We REPRINTED FROM
Wee Volume VII, Numbers 11-12, Pages 597-708,
OF THE
Monthly Bulletin of the State Commission of Horticulture
NATURAL HISTORY
OF THE
| GROUND SQUIRRELS
OF CALIFORNIA _
By JOSEPH GRINNELL and JOSEPH DIXON
Contribution from the University of California
Museum of Vertebrate Zoology
REPRINTED FROM
Volume VII, Numbers 11-12, Pages 597-708,
OF THE
Monthly Bulletin of the State Commission of Horticulture
NATURAL HISTORY
OF THE
GROUND SQUIRRELS
OF CALIFORNIA
By JOSEPH GRINNELL and JOSEPH DIXON
\\i %
Contribution from the University of California
Museum of Vertebrate Zoology
CALIFORNIA STATE PRINTING OBF
SACRAMENTO
ie yal fs
1— 43007
SS
CONTENTS.
Page
TMS NOMS. Sea ee eS Sapo) oie en ey es EGR fiat cht Ua 4
Introduction Re te a Sande ar LG pe cle Sy ere ere aoe 5
ANTES INO SKN 6
aixeyito the: Ground Squirrels of Californias 9220 == sans ss eS ee 8
(Caniitoraauley GChaohpiarel Crome vv ee ee ee ee 9
BEASTS Yen 1 oC ¥2 ULNA SS CUT Ta eae ap es ane Se 44
(Caraibi uiisieraal Cheonael Sioquiberele se eee eee 49
OW STASe, Gr OUT, SoU Te ee ae a aN ee ees Se ees 52
Rocks Squirrel: 2222) Ses oe Se Se ee ee ee a ee ees 58
ORES OG TOUT ys CU ge ee a ee ee ee 59
ARES Yh ra £53 Gyr ATT SS Ca Te ee 67
Stephense sort-haireda Grounds Squirnel aes eee ee 73
IMIGINE RS (Greowenel (SOW RS a eS 75
WUWOTONE) TRO WHO ENVieGl Chaobasl: Stonbuicreey i Sa es a ee 76
Deathevalley, Round-tailled=GroundsSquirrele==22 ee 80
Palme sprminesmround-taledsGround a SquiGtel 2s ee eee 81
SierraaGolden-mantled: Ground) Squirrel2ee222 25S Se aS ee eee 83
inane Colékemsceinilecl Chron Stories a 89
San Bernardino Golden-mantled Ground Squirrel_____.___-_______________ 92
Draseras Aways. (Creobboual (Syonb nena ss eo ee ee eS 94
Nelson FASTEST OP Cres GeO VANS Cp UT aa I TL ge RL tla Sea ein a 103
WosmBanos;-Antelope: Ground *Squirrela==s2 5 See eee 110
Summary of Points of Special Importance from the Standpoint of
Grounds Squirrels C omit ole a ANGE eh ales barker hae) Benne nue eee ee 112
NEAT RES GPE ELD een Cont Ke bees a ea ea oT eA ee eS ea 115
Norr.—Figures indicating page numbers refer to folios at foot of pages
ILLUSTRATIONS.
PLATES.
PAGE
Bleue. alee Ceibidonaavieh Chrobinclatsonvube nes) se 5)
Plate 2. Douglas Ground Squirrel and Oregon Ground Squirrel____-__________ 52
Plate 3. Belding Ground Squirrel and Sierra Golden-mantled Ground Squirrel__ %9
Plate 4. Yuma Round-tailed Ground Squirrel and Mohave Ground Squirrel____ 76
Plate 5. Desert Antelope Ground Squirrel and Fisher Ground Squirrel_—______ 98
FIGURES IN TEXT.
PAGE
Fig 1 Mans! Ob= SeVieralluSPECIESh Ollse S34 OU Gs S CUD Te CN Se eg aie 9
Fig. 2. , svoune Nelson Antelope Ground squirrela=232= ee eee 106
Fig. 29. Adult pair of Nelson Antelope Ground Squirrels____________________ 107
Fig. 30. Diagram showing relative economic importance of different ground
ESTO ADO i) 3) Sareea ce es RL eS SS ee a Se ee sii Seales air Ee) 114
Norr.—Figures indicating page numbers refer to folios at foot of pages.
NATURAL HISTORY OF THE GROUND
SQUIRRELS OF CALIFORNIA.
By JOSEPH GRINNELL and JOSEPH DIXON.
Contribution from the Museum of Vertebrate Zoology, of the University of
California.
INTRODUCTION.
Human occupancy of a new country always tends to upset the primi-
tive balance of things. Man either purposefully or incidentally begins
at once to modify the original complement of animal and plant life both
through destruction of native species and by bringing in with him alien
kinds. Some native species become more and more restricted in range,
even disappearing altogether; others tend to increase and spread,
finding conditions for their existence to be improved through man’s
activities.
In the case of the ground squirrels of California, we have a group of
mammals which seems to have in many places benefited by human
invasion. This is probably due to the destruction by man of the many
predatory animals, such as hawks, eagles, coyotes and badgers, which
under original conditions kept the small herbivorous mammals in check,
and in part to the improved food supply made available to the ground
squirrels through his cultivation of crops. Because of the destructive-
ness of these rodents to the planted crops and native forage upon which
man is dependent to a large extent directly or indirectly for his own
food supply, the problem of ground squirrel control has become one
of very immediate agricultural and pastoral importance.
It would seem that knowledge, as full as possible, of the ground
squirrels of California is necessary to determining the most successful
means of controlling them and to applying these means properly to the
varying conditions throughout our state. This knowledge should in-
elude the main distinctions by which each may be known from its
relatives, the distribution of each of the species, the extent of the bur.
rows, the breeding rate, the food habits, and, indeed, every other class
of facts obtainable relative to their natural history. It is not often
apparent, in advance, which facts will and which will not prove of
critical importance in economic work.
To illustrate the value of a thorough knowledge of the food habits
of the animal in question, when the most efficient method of controlling
destructive rodents is sought, we need only to point to the present
method used in poisoning the California Ground Squirrel by the use
of barley coated with strychnine, rather than barley soaked in a strych-
nine solution. By applying a knowledge of the food habits of this
animal it was possible greatly to increase the effectiveness of poisoned
grain because of the discovery by Stanley E. Piper, of the United States
Biological Survey, that this squirrel is more readily poisoned through
the membranous walls of its cheek-pouches when merely carrying the
poisoned grain than through the stomach after the poisoned grain
has been eaten. Strychnine-coated barley has not, however, been found
5
598 THE MONTHLY BULLETIN.
so successful when applied to the Oregon Ground Squirrel, which animal
apparently does not habitually gather and store seeds and grain to a
large extent, but is active chiefly during the spring and early summer
when green vegetation, upon which it depends for food, is to be had.
Some sort of green baits might be expected to be more effective with
this species.
It is very desirable at this time that we know more about. the extent
of estivation and hibernation among our ground squirrels. We know
little or nothing of the effect of gases upon squirrels in this condition ;
and it is obvious that such part of a squirrel population as is dormant
at the time of a poison campaign will escape destruction and become
a nucleus of reinfestation.
During the past spring and summer our work of excavating squirrel
burrows after the occupants had been gassed, has shown that one fre-
quent cause of failure in the ordinary waste-ball method of applying
carbon bisulphid is due to the fact that sudden elevation in the course
of the burrow, of as much as two feet in some cases, prevents the heavy
gas from reaching the animal. This condition was found to occur
much more frequently than is generally supposed.
The instances just cited all suggest that the present knowledge of
our ground squirrels is far from complete, and they serve to emphasize
the above contention that a more thorough knowledge of this subject
is essential to securing the most intelligent and efficient methods of
control of these our chief rodent pests. It is the purpose of the present
paper to supply the information available from all sources in as much
detail as it has proven feasible for the authors to secure it at this time.
The facts and inferences are given just as they came, irrespective of
whether or not they show obvious and immediate economic bearing.
They are here available to everyone who is concerned with methods of
control.
ACKNOWLEDGMENTS.
The present paper has been prepared at the suggestion of Mr. G. H.
Hecke, California State Commissioner of Horticuiture, and Mr. W. C.
Jacobsen, Superintendent of Rodent Control under this commission.
Both these men have rendered many valuable helps during the progress
of our work and have co-operated to facilitate its final publication.
Their emphasis all along has been upon the need of a summary of the
facts relative to rodent natural history at this particular time, when
efforts from every direction are being concentrated upon the problem of
increased crop production.
Upon the facilities and auspices of the Museum of Vertebrate Zoology
of the University of California the writers have been dependent for
the opportunity of carrying through their undertaking; and behind this
has been the continual financial and moral support of the founder and
constant patron of the Museum, Miss Annie M. Alexander. The eol-
lections of specimens and the field records contained in this Museum,
gathered during the past ten years, have been absolutely indispensable
THE GROUND SQUIRRELS OF CALIFORNIA. 599
to the present accomplishment. OO [st join] oases fem
a i ; tu ase : | nel!
10 CEE Pot EE EEE
a 4 on cI a fas
Pou Ces iH H saree HH EER g Suegseeceeea==—— a
Fic. 12. Diagram showing extent and height of breeding season in the California
Ground Squirrel. Heavy line shows percentage of females pregnant, for weekly periods
from January to May. Based on record of embryos found in over 10,000 females
examined by the United States Public Health Service (McCoy, 1912, p. 1070). -
Soon after the efforts against the squirrels were relaxed the latter
began to ‘‘spill in’’ from adjacent areas until now in places they are as
numerous as ever. Nevertheless the prime object was attained, that of
eliminating the foci of dissemination of the disease.
It is extremely important to know definitely the season and rate of
breeding of any economically important, rodent. Fortunately for our
purpose, there is available for the California Ground Squirrel abundant
data, supplied through the records of the United States Public Health
Service (see McCoy, 1912, p. 1070). As will be seen from the accom-
panying diagram (fig. 12) based on over 10,000 females examined, the
breeding season is restricted to a comparatively brief period of the
year. Pregnant female ground squirrels have been taken in the Bay
region as early as the first week in January, but the main breeding
season does not begin until February, and it is practically concluded
by the middle of April. The largest per cent of pregnant females is to
be found during the last week in February. By June 4 only two-tenths
of one per cent (0.2) of females examined contained embryos. At higher
26
THE GROUND SQUIRRELS OF CALIFORNIA. 619
altitudes, where warm weather comes on much later and more abruptly,
these breeding dates would be correspondingly later and the breeding
season still more restricted.
While males and females occur in practically equal numbers, mating
seems to be promiscuous; there is no permanent pairing off.
The number of young per litter, as ascertained from counts of
embryos, varies from 4 to 11. The average, from very extensive records
kept by the United States Public Health Service (McCoy, 1912, p.
1070), may be inferred to be very close to 7.2. The same records serve
further to show that there is some variation in size of litter from
month to month. The average for February is 6.9; for March, 7.3;
for April, 7.5; for May, 6.8. The tendency seems to be toward slightly
larger litters in April, which is beyond the date of maximum number
of pregnant females (see fig. 12). Number of mammez (nipples),
which is usually six pairs in this species, occasionally but five, is no
eriterion for number of young per litter. All the evidence at hand
indicates that each female raises but one litter each year. A female
ground squirrel was taken on the University campus at Berkeley, on
March 138, 1918, which contained eleven embryos each of which meas-
ured three-fourths of an inch long. Eight of these were contained in
one branch of the uterus and three in the other. Another female
taken at the same time contained eight embryos, each of which measured
five-eighths of an inch long. Five of these were in one branch of the
uterus and three in the other.
On April 6, 1918, G. R. Stewart and the junior author dug out two
female ground squirrels which had been previously gassed in their bur-
rows. One of these females was found in a nest with four small young
which we took to be about ten days old, since their eyes were not yet
open. These baby squirrels averaged 170 millimeters or 62 inches in
length; a typical one weighed 61 grams, or a little over 2 ounces.
They were well covered with hair, which already showed on the back
the characteristic dappled pattern of the adult squirrel. The tail,
however, was nearly round and showed little sign of the fringe of hairs
along the sides. Their stomach contents showed no sign of their having
eaten green vegetation or anything else than milk. Data from other
sourees indicate that the young are not completely weaned until they are
at least half grown. The other female secured in an adjoining burrow
not over ten feet distant was found to contain seven small embryos each
of which measured three-eighths of an inch in length. These embryos
could not well have reached full development short of two or three
weeks, so we have a variation of nearly a month in time of birth at one
locality.
Cases such as those just given are thought to be exceptional and may
serve in part to explain the occurrence of late litters such as have been
the basis of the claim that this animal has two litters a season. Litters
of young squirrels which sometimes appear very late in the season are,
too, likely to be merely the result of efforts to replace first litters of
young which have met an untimely death. Thus two litters might be
born in one season, though only one raised.
Shaw (1916, p. 4) gives 24 or 25 days as the period of gestation in
the Columbian Ground Squirrel (Citellus columbianus) in the region
about Pullman, Washington. The period of gestation of the California
27
620 THE MONTHLY BULLETIN.
Ground Squirrel has not to our knowledge been determined; yet the
facts at hand, such as the general rate of development of the embryos,
and of the young after birth, lead us to believe that it is close to thirty
days.
The bulk of the young ground squirrels in any one locality make
their appearance with remarkable uniformity as to size and regularity
as to date. Our data is incomplete, as to exact time of birth; but we
have plenty of records of embryos in various stages of development,
and we can observe the time of appearance of the young squirrels above
ground. In the lowlands the majority are probably born the last of
March, and by the last of April the first born are beginning to appear
aboveground, playing about the mouths of the burrows. In the higher
altitudes the young are born later. Females in the Transition Zone
and lower part of the Canadian Zone had not yet given birth to their
young in June. ‘‘Spring’’ in the lowlands comes in April, while the
spring of the higher altitudes does not occur until late June or July.
Hence the young do appear at the same season, considering the differ-
ences in temperature conditions at the different elevations. The
accumulation of a certain quantity of heat from without seems to be
necessary each year to start the squirrels breeding.
Young California Ground Squirrels may be considered fairly preco-
cious. They ordinarily begin to venture outside their nest burrows
when yet very small, in ascertained cases only cne-fourth or even one-
fifth the weight of the adults. They are then probably not over four
weeks old. At Snelling, Merced County, on May 28, 1915, C. L. Camp
(MS) observed that young ‘‘evidently just emerging for the first time
in their lives, seemed confused when they saw a horse and buggy and
often ran almost directly under the wheels.’’ Two months later, in
the high mountains, the young squirrels behaved the same way. A
probably abnormal occurrence was that of a very young squirrel found
on April 29 wandering aimlessly about in the grass near a burrow
entrance. This squirrel weighed only 61.5 grams, or less than one-
tenth the weight of adults. It was practically helpless and would have
fallen easy prey to any sort of predaceous animal.
The first litter of young ground squirrels seen aboveground in the
season of 1918 by the junior author was noted on April 28 at 1,500
feet altitude on San Emigdio Creek, Kern County. In this litter there
were six young at least one-third grown. Judging from the ‘‘sign’’
about the burrow, these youngsters had been foraging above ground for
a week or ten days. The season at this altitude was at least ten days
later than it was down on the lower parts of the San Joaquin Valley.
Several burrows of small diameter and amateurish construction were
found at the edge of a thick patch of alfilaria that grew near the nest
burrow. These young squirrels in spite of their small size were busily
harvesting the heads of the ripening alfilaria and when alarmed ran
down the small burrows which each had dug for himself. While the
observer was standing over one of these burrows a youngster came up
halfway out of a hole six feet away, but catching sight of him gave
a hasty alarm note and scurried back down the hole. Twenty-five
minutes elapsed after this before any of the young squirrels reappeared
above ground.
THE GROUND SQUIRRELS OF CALIFORNIA. 621
As far as is to be observed, the male takes no active interest in the
welfare of the young. Indeed, he dwells altogether separately from the
family and does not see his offspring until they begin foraging out of
doors. His only function at all, as regards the upbringing of the
young, is that of sounding general alarm throughout the colony when
danger threatens. As for the mother, even she is notably indifferent
to her young after they appear above ground. When suddenly alarmed,
she flees to safety on her own account, leaving the youngsters to shift
each for himself as best he may.
The rate of growth of the young is such that they reach mature size
by September, when they are from four to six months old (McCoy,
1912, p. 1069). But before this time, by the first of August, the young
of the year begin to emigrate locally, so as to establish each for himself
anew home. It is hkely that this process of emigration is hastened by
the development on the part of the parents of an attitude of incom-
patibility. According to this idea the initial solicitude of the mother
for her young at the helpless age is later reversed, so that she becomes
antagonistic to them and finally speeds their departure. The young,
at the same time, begin to give evidence of an instinct to wander. At
any rate, the month of August sees the important phenomenon of emi-
eration or dispersion well under way. Young of the year then put in
their appearance in unexpected places; new ground is invaded, and
the total territory occupied by the squirrels increased in extent insofar
as the increase in population makes necessary and the favorable nature
-of the country permits. Undue congestion of population tends thereby
to be prevented.
The natural enemies of the California Ground Squirrel are of many
kinds, and under original conditions so many as regards individuals
as to provide a regular automatic check to any abnormal increase of
the squirrel. The most important are golden eagles, red-tailed hawks,
coyotes, badgers, wildeats, weasels, rattlesnakes and gopher snakes.
Each of these various animals pursues the squirrels in its own particular
way. Hawks and eagles swoop down on them from their vantage points
in the air. Wildcats and coyotes lie in wait near the burrows until
the squirrels venture forth in search of food, when they pounce upon —
them. Badgers, weasels and snakes capture the squirrels in their bur-
rows. Some specific cases will be cited here. It must be remembered
that, while casualties to squirrels may be inflicted by their customary
enemies almost hourly in any general neighborhood where man has not
exterminated these predators, the chances of a person’s being in a
position at the critical moment to witness a tragedy of this sort are rare.
At the San Emigdio Ranch in Kern County on April 25, 1918, the
junior author watched a Golden Eagle (Aqwila chrysaetos) capture and
devour an adult ground squirrel. The eagle was first observed flying
quietly down a canyon. By weaving in and out in its course the bird
was able to skirt the irregular hillside so as to keep within fifteen or
twenty feet of the ground. At length the eagle skimmed abruptly
around the shoulder of a hill, just clearing the tops of the wild oats,
and dropped quickly down upon a luckless ground squirrel. The latter.
had evidently been on a foraging expedition and did not have time to
reach his burrow, so complete was the surprise. The eagle seized the
squirrel with both sets of talons, and the piercing grip by these effective
29
622 THE MONTHLY BULLETIN.
instruments quickly dispatched it. The bird then proceeded to tear
the animal to pieces with the stout beak and, perched on the ground,
devoured it on the spot. The strategy and success of this method of
attack was obviously dependent upon the eagle keeping close to the
ground so as to remain out of the squirrel’s range of vision until the
last moment.
At Pleasant Valley, Mariposa County, on May 17, 1915, C. L. Camp
(MS) fed a ground squirrel that had been shot, to a Golden Eagle kept
captive by a storekeeper there. The eagle ate head, skin and bones,
but discarded the stomach and large intestines. Other birds, such as
the turkey vulture, have been observed by the junior author to similarly
avoid the stomach and intestines of ground squirrels that have been
killed by taking poisoned barley. Coyotes have also been known to
show the same fine discrimination when eating ground squirrels which
they themselves have not caught.
Some idea of the success with which Golden Hagles sometimes pursue
ground squirrels may be had from the fact that at Lilac, San Diego
County, on April 4, 1907, James B. Dixon (MS) found eleven freshly
caught ground squirrels in and about an eagle’s nest that contaimed
two eaglets about a week old.
During the spring of 1904 W. L. Finley and H. T. Bohlman observed
and photographed a pair of young Golden Eagles in various stages of
development from the time the eaglets were nine days old until they
left their birthplace nearly three months later. The aerie was a bulky
affair placed in a horizontal fork of the upper limbs of a large sycamore
tree that grew in a canyon back of Mission San Jose, Alameda County.
In speaking of the food of the Golden Eagle, Finley (1906, pp. 9-10)
says: ‘‘His food consists almost entirely of the ground squirrels that
are so abundant through the California hills. On our second trip [on
April 12], when we looked into the nest, we found the remains of the
bodies of four squirrels lying on its rim. At each visit we examined
the food remains and the pellets about the nest, and we are sure that
a very large proportion of the eagles’ food supply consisted of squirrels.
... 1 am satisfied that this family of eagles regularly consumed an
average of six ground squirrels a day during the period of nesting,
and, very likely, more than that. . . . But even this low estimate would
mean the destruction of 540 squirrels along the hillsides in about three
months’ time.’’
The nest of a Western Red-tailed Hawk (Buteo borealis calurus)
examined by J. B. Dixon (J. Dixon, 1917, p. 12) on March 28, 1906,
and containing one day-old chick, two pipped eggs and a rotten egg,
was found to contain also the remains of two ground squirrels. This
was near Vista, San Diego County. At Pala, in the same county, the
same observer found the nest of a Red-bellied Hawk (Buteo lineatus
elegans), April 3, 1916, containing three young, a week old, together
with one ground squirrel and two pocket gophers. The dead squirrels
counted in the nests represent, of course, merely the surplus which the
old birds had just carried to the young. The squirrels that the old
birds themselves or the young may have eaten on the day of observation
are not taken into account.
At Dunlap, Fresno County, on September 30, 1916, H. S. Swarth
(MS) found a large rattlesnake (Crotalus oreganus) which showed a
30
THE GROUND SQUIRRELS OF CALIFORNIA. 623
bulge in the middle portion of its body. ‘This proved to mark the loca-
tion of a full-grown ground squirrel, which had been swallowed entire,
head first.
Near the mouth of Tejon Creek, Kern County, on July 16, 1914, C. L.
Camp (MS) watched a rattlesnake (Crotalus oreganus) about three
feet and a half long, swallow a ground squirrel. He describes the
incident essentially as follows: The snake had just bitten the squirrel
on the side of the face below the eye. The squirrel flopped about for
five or ten minutes and then dropped over a bank and died, out of sight
of the snake. The snake then slowly crawled down over the bank after
its prey, found it, touched it all over with the end of its tongue, and
then seized the animal by the nose. The squirrel moved slightly. The
snake drew back and waited motionless for some time. The snake then
got a fresh hold on the squirrel’s nose, pulled the body out straight,
and started to work its jaws over the squirrel’s head. Things went
rapidly as far as the squirrel’s ears, then operations proceeded more
slowly. The snake writhed about and gradually worked its jaws over
the shoulders of the squirrel, first moving the upper jaw forward with
slight jerks and then pulling up on the lower jaw. Finally, after the
rodent had been half swallowed, we approached closer to take a picture
and the snake disgorged the squirrel as the result. of a violent effort
lasting a minute or so. We went away and in a little while the snake
returned to its food and had swallowed it almost ome toy, within
15 or 20 minutes more.
On Pine Flats, in the San Gabriel iene, a lanes, lazy rattler
was secured which showed a bulge about halfway, along its body. Dis-
section disclosed a full-grown California Ground Squirrel which had
been swallowed. (Grinnell, J. and H. W., 1907, p. 53.)
On San Emigdio Creek, Kern County, on the morning of April 23,
1918, the attention of J. Dixon (MS) was attracted by the nervous
barking and peculiar actions of a large male ground squirrel. With
the aid of the binoculars, the actions of the squirrel, which was less than
75 yards distant, were easily followed. The squirrel was obviously
much wrought up and his sharp, nervous notes were quite different in
pitch and intensity from the ordinary metallic alarm note. The ani-
mal’s attention was continually focused upon an opening just beneath
a certain small white rock at the edge of a stone pile. While his atten-
tion thus remained fixed, the squirrel kept running back and forth in
a semicircle about thirty inches distant from the object concerned.
During this time the squirrel’s tail, which was held arched over his
back, was twitched violently sideways every time he barked. The
alarm notes were uttered during a momentary pause at the end of
each advance in the are-shaped path of the squirrel. The squirrel’s
whole demeanor reminded the observer of that of a pup that has cor-
nered some old pussy cat and still hesitates to make an attack. Having
witnessed three similar performances by ground squirrels, in San Diego
“rounty, the observer proceeded to investigate and found, as in the three
previous instances, that a coiled rattlesnake was the cause of the excite-
ment. In the present case there were two, a male and female, tightly
coiled together at the mouth of a squirrel burrow, and they were dis-
patched. An hour later this same squirrel, which was easily identified
by a peculiarity in its pelage due to wear, was observed digging a new
31
684 THE MONTHLY BULLETIN.
burrow some fifty feet distant from where the rattlesnakes had been.
There was no way of determining whether the presence of the snakes
had influenced this action, but it was evident that this squirrel made
no effort to fill up the entrance to the burrow which had been pre-
empted by the snakes. It is a popular notion that ground squirrels,
when the opportunity offers, bury snakes alive.
As for mammals as enemies of ground squirrels, the evidence most
readily obtainable is derived from examination of the excrement of
the former. Coyotes have regular places for deposit of excrement, on
hill tops or ridges. Bones and teeth of ground squirrels frequently
have been found represented in these deposits (J. Grinnell, MS). The
remains of two freshly eaten ground squirrels were found in the stomach
of a wildcat killed in central San Diego County (J. Dixon, MS).
As to food, the California Ground Squirrel shows a wide range of
taste, even though there are at the same time decided preferences. He
cheerfully adopts substitutes when favorite foods are lacking; he is
not averse to taking considerable barley with his wheat. A list of all
the plants eaten by the ground squirrel would be a very long one, and
if locality be taken into account great variation would doubtless be
found from place to place. The above general statements will be borne
out, in part at least, by the data presented in the paragraphs to follow.
On the University campus at Berkeley, on March 13, 1918, the ma-
jority of the California Ground Squirrels were feeding on the tender
leaves of alfilaria (Hrodium). A female squirrel was observed by the
junior author at this time to eat the leaves of young plants of the star
thistle (Centaurea). On San Emigdio Creek, Kern County, on April
28, 1918, a squirrel was seen to disappear down a hole carrying a sheaf
of freshly cut heads of foxtail (Hordewm) held tightly in his mouth.
A few minutes later this squirrel was gassed and when the burrow was
dug out the fresh foxtail heads were found on the edge of the nest.
Previously this squirrel was seen to gather heads of both foxtail and
alfilaria, but preference was given to the latter (J. Dixon, MS). The
young as well as the old squirrels seem to prefer alfilaria when obtain-
able to any other plant.
In the region about Walnut Creek, Contra Costa County, on July 26
and August 16, 1918, the authors found ground squirrels feeding exten-
sively on seeds of bur clover (Medicago hispida). . Dried burs of this
plant were abundant on the hillsides in the near vicinity of the squirrel
burrows, and although there was a plentiful supply of barley on the
adjacent stubble fields this was in major part passed up in favor of
the clover seeds. Hulled seeds of the bur clover were found to pre-
dominate in the cheek pouches and the stomachs of the score or more
squirrels that were shot. This fondness on the part of the ground
squirrels for bur-clover seed suggests a possibly better way of poisoning
these rodents by using the entire bur of the clover than by the use of
barley, wheat or other grains, which are now so padiy needed for human
consumption.
In southern California the seeds of the plant known as wild cucumber,
manroot, or chilicothe (Echinocystis macrocarpa) is eagerly sought by
ground squirrels. Gnawed hulls of the seeds of this plant are fre-
quently found in large quantities near the summits of rock piles where
the husking or lookout stations of the squirrels are located. In Yosemite
32
THE GROUND SQUIRRELS OF CALIFORNIA. 625
Valley a ground squirrel was seen gathering green fruits from the top
of a four-foot manzanita bush.
C. H. Merriam reports (1910, p. 5) that the seeds of the manroot
(Echinocystis fabacea) are eaten in the vicinity of Modesto from the
middle of May to the middle of December. The seeds are eaten from
KO Oy Fp y
may
OP rr
b
Fig. 13. Drawings from dissections to show relative extent
of cheek-pouches in (a) California Ground Squirrel and (b)
Belding Ground Squirrel. One cheek-pouch opens into the
mouth cavity on each side; it is lined with membrane contin-
uous with that lining the mouth and is used for carrying food
materials such as seeds and bulbs from the forage ground to
either the store house or the husking place. It is to be inferred
that the California Ground Squirrel is much more of a seed-
gatherer than the Belding. The latter, like the Oregon Ground ©
Squirrel, is more of a grass-eater, and also does not garner
food io the extent that the “digger” squirrels do.
the time they begin to form until they are fully ripe. ‘‘Other favorite
seeds are those of elderberry (Sambucus), jimson weed (Datura), wild
nightshade (Solanum), turkey mullein (Hremocarpus), tarweed
(Madia), and numerous grasses. . . . In southern California the
squirrels are fond of the fruit of the prickly pear (Opuntia).”’
_ Ground squirrels are provided with more or less extensive, membrane-
lined cheek pouches opening inside the mouth, which are used in gather-
ing and transporting food (see fig. 13). Often when the animals are
seared out of weed patches or bushes, or away from some supply of roots
33
3—43007
626 THE MONTHLY BULLETIN.
or bulbs which they have discovered, their cheeks are seen to be bulging
with the contents of these pouches. They are able to operate their
teeth and lips even when these pouches are copiously distended. The
cheek pouches of the California Ground Squirrel are especially well
developed and this, we think, is correlated with the pronounced seed
gathering and storing propensities of this species. The following rec-
ords of cheek-pouch contents, as secured from specimens collected,
contribute further to our knowledge of the kinds of food of this animal
and also of the quantity in which these may be gathered.
A female taken in a stubble field near Walnut Creek, Contra Costa
County, July 26, 1918, held in her cheek pouches 26 seeds of bur clover.
A male taken August 15, 1918, at the same place had 78 seeds of bur
clover and one seed of needle grass. Two other males had one and
three bur-clover seeds, respectively. Another female taken at the same
time and place contained 212 seeds of bur clover and 12 seeds of some
kind of wild grass. Another male held 97 grains of barley and three
bur-clover seeds. A ground squirrel taken at Cisco, Placer County, on
October 9, 1913, was carrying 92 seeds of the green manzanita (Arcto-
staphylos patula), while a squirrel secured near Pleasant Valley, Mari-
posa County, on May 28, 1915, had dug up and was earrying in its
pouches 12 bulbs of a species of wild hyacinth (Brodiwa hyacinthina).
At El Portal, Mariposa County, a squirrel was secured with three large
acorns of the golden oak in its cheek pouches.
We will now consider those feeding habits which make the California
Ground Squirrel come into conflict more directly with man’s interests.
‘‘Of cultivated nuts, almonds and walnuts are preferred; of other
crops, apples, prunes, peaches, apricots, figs, olives, . . . the seeds of
cantaloupes, watermelons and citron melons, and all the grains are eaten
whenever they are to be had, and green alfalfa and clover are sometimes
taken’’ (Merriam, 1910, p. 5). Frank Stephens (1906, p. 66) has
summed up the food taken by this animal as follows: ‘‘The food is
principally of a vegetable nature, preferably grain and other seeds,
fruit, potatoes, green plants, ete. Eggs of poultry and wild birds are
relished.’’ We have heard considerable testimony from ranchers to
the effect that individual ground squirrels in different localities have
learned to raid henneries, so that the above statement is not exceptional.
A great deal of damage is done by California Ground Squirrels each
year in orchards and vineyards. The following instances, given by
Merriam (1910, p. 6) are typical of such depredations. ‘““Ground
squirrels are particularly fond of green almonds and of the pits of
green peaches and apricots, eating these from the time the kernels begin
to form until the fruit is ripe, thus doing serious damage. They are
very destructive to apples also, and in places in the foothills of the
Colfax-Auburn region are said to take fully half the crop. ... In the
fall of 1907 E. A. Goldman reported that they were doing serious dam-
age to young vineyards about Orosi, in Tulare County, by biting off the
leaves and tender shoots of the vines.... Im the orange groves
between Porterville and Springville, in Tulare County, it is reported
that they occasionally gnaw the bark of the orange trees and sometimes
cut the fruit and carry it off. Besides destroying nuts and fresh fruits
they attack drying prunes and carry off large quantities.’’
34
THK GROUND SQUIRRELS OF CALIFORNIA. 627
On May 14, 1918, near the mouth of Caliente Creek wash, Kern
County, in one corner of a 640-acre field planted to wheat, four large
bare spots were counted by the junior author in an area of not over ten
acres. These denuded areas were circular in shape and averaged 75
yards in diameter. They were caused by the ground squirrels having
eaten and destroyed the ripening wheat and even the stalks so that
nothing but weeds remained. In a single one of these denuded areas
twenty-three occupied squirrel burrows were counted. In this same
field, within a six-foot circle the center of which was a lone squirrel
burrow, 113 heads of wheat were picked up (see fig. 14). These heads
Fic. 14. These 113 heads of wheat were picked up within a six-foot circle, the center
of which was a “digger” squirrel burrow situated in the edge of a wheat field. They
were part of what had been gathered within three or four days, apparently by the one
squirrel.
had all been cut and carried to the burrow within three or four days,
as they were not yet dry. This was evidently the work of a single
squirrel, since no other squirrel was seen to go near the burrow. These
113 heads of wheat probably constituted part of what was intended for
storing, and did not include that required for current consumption.
In gathering food California Ground Squirrels slink along slowly
close to the ground, often half hidden in the grass. In gathering ripe
alfilaria only the clusters of seed cases are taken, with relatively little
of the stem. However, when the plants are young, the stems and leaves
are much relished by the squirrels. The usual method of feeding as
revealed by the binoculars, is for the squirrel to sit up on his haunches
within reach of the alfilaria heads, which are dexterously gathered into
little bunches by the front paws of the animal and then quickly snipped
off by the sharp incisor teeth. During this last operation the head of
the rodent is often inclined to one side. In gathering bulky food ma-
terials such as the heads of foxtail the cheek-pouches are not always
used, the material being carried crosswise in the squirrel’s mouth directly
to the burrow.
On the San Joaquin River near Mendota R. M. Hunt (MS) reports
seeing squirrels go cut into the tules of the sloughs seemingly to eat the
35
628 THE MONTHLY BULLETIN.
green stalks. Several times on following up rustling sounds squirrels
were discovered on thick mats of dry fallen tules among the standing
green ones and just above the water. One, on being alarmed, jumped
into the water with a splash and, although lost to sight, probably
reached safety by swimming. Davis ‘““Tsland,’’ near Mendota, is part
of the mainland at low water, but in May, with high water, becomes a
true island and with the highest water the ground everywhere is com-
pletely submerged. On June 20, 1918, a squirrel was discovered on
this island. It jumped from a piece of ground into the water and
swam, in much the manner of a dog, to a tree up which it took refuge.
Fic. 15. Metropolis of ‘digger’ squirrels under a small oak on a grain-sown hill-
side; photographed near Walnut Creek, Contra Costa County, ‘August 15, 1918.
Owing to the dryness of the season and to the depredations of the squirrels, the grain
on the hill above the oak had been left uncut.
A current report was to the effect that each year at high water ground
squirrels are marooned on this island and live for the time being in the
big hollow-trunked willows there. This shows that flooding does not
necessarily drive out or drown these squirrels in such localities as afford
refuges on high ground or in trees.
On wild land, alfilaria, foxtail and bur clover are perhaps the three
plants that are eaten to a greater extent than any other of our forage
plants. Alfilaria is eaten from the time it appears above ground until
it ripens, and even after that, when the seeds have scattered out, they
are gathered and either eaten at once, or stored. The long, curled
‘‘propellers’’ are broken off and discarded. In Strawberry Canyon on
the University campus, in April, the squirrels were harvesting foxtail
and alfilaria on sunny southern exposures where the plants had matured
early. Later in the season, during late June and early July, these same
squirrels with their families of half-grown young were found to have
moved down the hillsides, some 150 yards, to the moister, shady ground
near the creek bed where the foxtail was still green, and here they were
busily gathering the foxtail heads just ripening on July 6. There is
an obvious rotation in the use of the different important plants for food,
36
THE GROUND SQUIRRELS OF CALIFORNIA. 620
dependent upon the sequence in which they become available. Thus,
alfilaria is eaten during winter and early spring; then the foxtail crop
claims attention; and the bur clover, after its seeds ripen, is harvested
all through midsummer and autumn. Of course the above statements
are only of local application.
Examination of the food stores of ground squirrels would go far
toward providing adequate knowledge of their food habits. Such inves-
tigations should be made preferably in the fall. Specific information
now available is as follows: |
In digging out a colonial burrow near Bakersfield, Kern County, on
May 3, 1918, a storehouse was uncovered. This consisted of a cavity
or pocket off the main run (see a, fig. 8), which measured five and a
half by eight inches in two diameters and was eighteen inches beneath
the surface of the ground. ‘The stored food consisted of a double hand-
ful of nearly dry heads of foxtail grass carefully packed in dry sand.
A few alfilaria seeds were also included with the foxtail, but alfilaria
was scarce at this locality.
Upward of fifty of the button-like seeds or ‘‘cheeses’’ of the mallow
(Malva) were observed at the entrance of another burrow at the same
place, but the observer was unable to determine whether or not these
seeds were being stored. The mallow seeds were found for the most
part on the lookout station at the entrance to the burrow.
“*A¢ Modesto in May, 1909, Piper found stores of alfilaria seeds
packed in cavities and well mixed with dry sand. In December of the
same year he examined a number of stores of grain unearthed by a
farmer while scraping and leveling his land. Each of these caches
consisted of from a pint to a quart of oats stored in cavities and packed
in dry sand. They varied from 8 to 18 inches in depth beneath the
surface; some were in short blind holes; others at the ends of branches
of the main burrow’’ (Merriam, 1910, p. 5). 5
An idea of the quantity of food eaten by the California Ground
Squirrel can be derived from the following data:
A female taken near Coulterville, Mariposa County, on June 3, 1915,
weighed 553.5 grams, or about a pound and a quarter. The stomach
and its contents alone weighed 77.5 grams, or about 22 ounces (C. L.
Camp, MS). Figuring out the ascertained weight of the stomach in
other individuals, 5 grams, the ratio of stomach contents to total weight
in this squirrel proves to have been about 1 to 7. The material repre-
sented is presumed to have been fresh green stuff.
Some experiments have been carried on at the Museum with captive
squirrels with the purpose of determining the amount of green forage
consumed daily. Fifty grams, or nearly two ounces, of green alfilaria
was found to be the average daily ration for an average-sized squirrel.
In cases where all food had been withheld from the squirrels the previ-
ous day, the greatest amount of succulent alfilaria, the favorite food of
the squirrel, consumed in one day was 80 grams, or somewhat less than
three ounces.
Five immature ground squirrels taken July 26, 1918, near Walnut
Creek, Contra Costa County, gave an average total weight of 504.3
(427.2-517.2) each in grams. The average weight of the stomach con-
tents in these five squirrels was 13.2 (10.3-19.0), so that the average
ratio of the weight of the stomach contents to the total weight was
37
630 THE MONTHLY BULLETIN.
1 to 38 (1 to 50-1 to 22). The stomach contents in these cases con-
sisted almost entirely of finely chewed seeds of barley and bur clover.
The squirrels were shot between noon and 2 p.m. Seven full-grown
males taken on August 15, 1918, near Walnut Creck, gave an average
total weight of 659.4 (576.8-724.7) grams each; the average weight of
the stomach contents was 17.9 (11.5-20.5); and the average ratio of
contents of stomach to total weight was 1 to 37 (1 to 63-1 to 30).
Seven full-grown females taken at the same time and place gave an
average total weight in grams of 500 (370.7-681.4) each; the average
weight of the stomach contents was 9.7 (5—-15.8) ; and the average ratio
of contents of stomach to total weight was 1 to 42 (1 to 101-1 to 37).
All these fourteen squirrels were foraging in stubble fields, and the
stomach contents consisted of barley and bur clover seeds finely chewed
and of nearly the same degree of moistness as ordinary baker’s dough.
The squirrels were shot between 10 a.m. and noon.
It is believed by us that two ounces of green forage or one-half ounce
of dry grain is an average stomach-full for an average-sized California
Ground Squirrel and that two stomach-fulls represent a day’s ration.
It is evident that the proportion between the weight of the stomach
contents and the total weight averages considerably less in this species
than it does in the Oregon Ground Squirrel. The California is more
of a seed eater and less of a grass eater than the Oregon Squirrel and
therefore enjoys a more condensed ration.
During late summer digger squirrels, particularly the old adults,
become exceedingly fat. In this condition they become obviously lazy
and may often be seen lounging at the entrances to their burrows sim-
ply enjoying the sunshine. As the season farther advances, a decided
decrease in squirrel population is noted. The active young of the year
are still foraging abroad, but even these restrict their activities to the
brightest hours of sunshiny days. What becomes of the squirrels which
have altogether disappeared underground ?
One would naturally expect that the life history of such a notorious
animal as the California Ground Squirrel would be known pretty
thoroughly. However, such does not seem to be the case; there are sev-
eral features of the underground life of this squirrel in regard to which
our information is very inadequate and of which from the standpoint of
rodent control it would be most useful to know. As has been previ-
ously mentioned, little appears to be definitely known regarding the
period of gestation of this animal. The condition of the young at birth
and their subsequent care and development is also not well known.
Another moot point is that of estivation or hibernation of this species
of ground squirrel. Merriam (1910, p. 4) states that ‘‘this species
does not hibernate, except in the mountains, although in the foothills
and valleys the animals usually stay in their burrows during stormy
and severe weather. At the upper limit of their range, where the
ground in winter is covered with snow, they may remain underground
long enough to be said to hibernate, but over the greater part of the
state they are out in numbers every month of the year.’’ However,
we believe we have evidence to indicate that a period of xstivation or
hibernation (or the two combined), in other words a state of torpidity
initially induced by the heat and dryness of summer, obtains among
some at least of the adult ground squirrels even in the lowlands. This
38
THE GROUND SQUIRRELS OF CALIFORNIA. 631
- period of dormancy extends from late summer well through midwinter,
and thus ‘‘sestivation’’ may be said to go over directly into true hiber-
nation. The old adults seem to be the only ones that ‘‘hole up,’’ for
the young adults somewhat less than a year old, that is, the young of
the year, may be seen about the burrows during suitable weather
throughout the winter.
In support of the above belief, that a period of torpidity overtakes
the older individuals of the squirrel population regularly each year, the
following evidence is submitted:
(1) Close watch, extending over a period of between four and five
years, was kept on a female ground squirrel that lived in the dooryard
at the home of Mrs. Elizabeth Grinnell in Pasadena. This particular
squirrel did not xstivate until its second year. Then and during each
succeeding year of its life it «stivated regularly, becoming very fat and
retiring to its burrow during the last week in August. It emerged
lean and hungry, with marked regularity, about the twenty-second of
each following February. When removed from the burrow at intervals
during this period, the squirrel was found to be in a torpid state, with
respiration not perceptible.
(2) In a ease in the junior author’s personal experience, near Escon-
dido, San Diego County, all the squirrels that were active in a certain
field in the fall were poisoned or otherwise killed, and yet old breeding ©
squirrels suddenly appeared in this same field the following February.
This occurred when there was seemingly no possible chance for rein-
festation from the surrounding fields, which had been cleaned up also.
Similar testimony has reached us from a number of men identified with
efforts to exterminate these rodents.
(3) It occurred to the present writers that it might be possible
through the examination of specimens to learn the extent to which old
adults are out in midwinter. The heads of 186 ground squirrels were,
at our request, secured by the United States Public Health Service,
shot and trapped near Martinez, Contra Costa County, during January,
1918, and sent to the Museum of Vertebrate Zoology, where the skulls
were cleaned and carefully examined. Relatively advanced age was
determined from the skulls upon the following criteria: general size,
zygomatic breadth, breadth of jugals, stoutness of postorbital processes,
degree of development of sagittal crest, degree of approach of parietal
ridges, breadth and degree of concavity of frontal surface, advance
in coalescence of the adjacent bones along certain sutures, and amount
of wear on the crowns of the molariform teeth.
The results of our examination are given in Table II:
TABLE II. Proportions of adult to young ground squirrels abroad in midwinter.
|
|
Total | Number Number Ratio of
Date received (in 1918) | number of | ofold | of young | old adults
| skulls | adults adults | to total
Bean Lasy, Bae eee sain he eA i axaTs) etal 1 fe 1 to 18
EERON DEE 7 Ce ee 34. | 4 30 | Ito 85
ETM A TY ps2 De CA ee SE RNs ee 86 18 68 | lto 4.7
RIE WOES 29 ea Cee a cee 48 11 | 87 | lto 4.3
The foregoing data are not nearly as complete as could well be desired,
but as far as they go they show that ‘‘old adult’’ squirrels are relatively
39
632 THE MONTHLY BULLETIN.
scarce aboveground in January as compared with the younger animals,
those probably less than one year old. Further, the proportions of old
to young increases rapidly towards the last of that month; in other
words, as the breeding season approaches. It is probable that the full
old-adult population is not abroad aboveground until the last of Feb-
ruary, when the ratio of old adults to young of the previous year would
certainly not be nearly so little as 1 to 4, which is the minimum possible
at the immediate close of the breeding season.
In spite of the above lines of evidence, the real extent of this habit of
estivation among our ground squirrels is not satisfactorily known. It
is exceedingly difficult to follow any individual squirrel under perfectly
normal conditions through all its various activities for any great length
of time. However, an important factor concerned in the work of
destroying these animals is suggested ; that is, the desirability of placing
emphasis upon the need of poisoning in the spring rather than in the
fall, when part of the breeding stock may be stowed away out of the
reach of poisoned grain. It is a question, too, whether or not a dormant
animal, in which respiration is extremely slow, would be fatally injured
by a fumigant before the latter would be dissipated.
Human interest in the California Ground Squirrel naturally concerns
itself most especially with the questions of total population, rate of
increase, and rate of re-invasion of territory previously cleaned of squir-
rels. As to the first question, we have founa it difficult to find an
accurate basis for determining the squirrel population living on any
given unit of area, such as an acre or a square mile. Counts may be
taken of living squirrels that happen to be aboveground at any one time,
or of burrows which give evidence of current use. In the first ease
the count is never likely to cover all of the squirrels in the area, because
the chances are overwhelmingly against all of the squirrels being above-
ground at one time. Season of the year, time of day, and state of
weather will affect profoundly this proportion of squirrels below ground
to those in sight. In the latter case some sort of estimate of ratio of
squirrels to burrows must have been arrived at. Season of the year
must again figure importantly in the estimate, because of the jump im
population following the breeding season, and progressive decrease
thereafter.
On July 26, 1918, the authors took two censuses of ground squirrels
on a badly infested ranch about three miles northwest of Walnut Creek,
Contra Costa County (see fig. 16). The first census was taken on a
south-facing hillside on an area 100 feet square, approximately one-
fourth of an acre. Three counts gave 19, 16 and 17 squirrels, respec-
tively, in sight at once. ‘Twenty-five open burrows were counted in
this area. This, therefore, was at the rate of 76 squirrels and 100
burrows per acre, or 14 burrows to each squirrel. The breeding season
at that date was well passed. Allowing one adult to every four young
gave fifteen adults to every 100 burrows or between six and seven open
burrows to each adult squirrel after the breeding season.
The second census was taken in a mowed field from which a crop of
barley hay had been recently harvested. The area taken was on a north
slope and measured 250 feet square, covering about 14 acre. Three
counts were taken between noon and one o’clock. The number of squir-
relg seen out at once was 25, 26 and 25, respectively. Sixty burrows
40
THE GROUND SQUIRRELS OF CALIFORNIA. ~ 633
were counted in this area, so that the infestation was at the rate of 20
squirrels and 50 holes per acre. This is at the rate of 24 burrows to
each squirrel.
On May 28, 1918, a single isolated colony was investigated at a point
twelve miles west of Fresno. This colony was in a plowed field which
had been planted to grain for several years past. Here, in an area 100
feet square 16 squirrels, eight of which were less than half grown, and
17 burrows were counted. The ratio here was close to one burrow to
each squirrel. This figure, again, applies to a period after the close
Fic. 16. Hillside near Walnut Creek, Contra Costa County, badly infested with
“digger” squirrels. On August 15, 1918, squirrels were here present at the rate of
fifty per acre. From this breeding ground they were at this time invading the grain
fields on the opposite slope.
of the breeding season, when the squirrel population had reached its
maximum.
Counts taken before the breeding season naturally give different
results. At Berkeley on March 13, 1918, the junior author counted 47
squirrel burrows in a colony which occupied about one acre on a hillside.
By counting the squirrels which appeared aboveground in this area on
several successive days it was ascertained that there were about nine
adult squirrels inhabiting this acre of ground. This gave an average
of over five burrows to each squirrel.
The above-cited instances are based on maximum infestation. Local
distribution is often very irregular, since squirrels may be abundant on
the southern exposure of a hill and yet be entirely absent on brushy
northern slopes only a hundred yards or so distant. Even on the plains
and in the valleys, although the distribution is much more uniform,
there is often marked unevenness in infestation irrespective of human
interference. Surgeon John D. Long (1912, p. 1596), in comparing
the cost of the various methods of destroying ground squirrels, based
his estimates of cost on an infestation of ten holes per acre. Presum-
ably, this was taken as representing an average infestation according to
41
634 THE MONTHLY BULLETIN.
the experience of the United States Public Health Service in their
eradication work. This appeals to us as a fair estimate on well-popu- .
lated territory, such as that around San Francisco Bay.
It is the authors’ belief that if the entire area in California occupied
by this species be taken into consideration a population of one squirrel
per acre, or 640 per square mile, at the conclusion of the breeding season,
would be a fair average. At this rate there would be a total population
of 32,000,000 California Ground Squirrels in the state in July, and one-
fourth this, or 8,000,000, in March, before the young of the year are out.
If the closely allied Fisher and Douglas ground squirrels be included,
as from an economic standpoint might well be done, the ‘‘digger squir-
rel’’ population of the state in summer, when crops are maturing, may
be put at between 40 and 50 millions, in this state.
As for rate of increase, we are dealing with a prolific animal. As
_already shown, the average size of the litter in the California Ground
Squirrel numbers practically eight. Males and females are present in
a general population in about equal numbers. Even though but one
litter is reared by each female squirrel each year, this would mean that
for each pair of squirrels at the beginning of the breeding season there
will be ten individuals at the close of the breeding season. The evidence
we have examined goes to show that all the squirrels breed the first year
of their lives—that is, when each is not quite one year old—as well as
subsequently, and that the life-time of a squirrel, if it dies of old age, is
five years. If we do not count upon any fatalities, one pair of squirrels
can be reckoned on to give origin to a population in five years of 6,250!
In recent efforts to eradicate squirrels a 90 per cent efficiency has
been currently estimated. This means that, if no follow-up campaign
be waged, ten squirrels out of each original 100 will be left, to form a
nucleus of future increase. At the end of the second year the popula-
tion would be back to normal. Supposing, further, that a follow-up
campaign is waged at the end of a suitable interval before the next
breeding season, also with a 90 per cent effectiveness; then only one
squirrel per original hundred would be left. Even then, when only
six squirrels are left on one square mile, these in the third breeding
season will produce, barring normal fatalities, the original 640, with
a good margin to spare.
The factors limiting the population of ground squirrels under nat-
ural conditions, that is, as not affected by human agency, include the
following, in the order of probable importance: (1) Quantity of food
available at the season of the year when food is scareest; (2) natural
enemies, including predatory mammals, birds and reptiles; (3) adverse
weather conditions, recurring rather infrequently, as when territory is
inundated during exceptionally heavy rains; (4) disease; (5) old age.
The rate of increase, through long ages, has been adjusted to more than
meet the expected death rate from all causes combined. This rate of
increase, fourfold each year, is now inherent and we have no reason
for expecting any abrupt and permanent change in it either way.
With the arrival of the white man and his accessories in California,
the natural balance has been upset. Man has destroyed a large per-
centage of the natural enemies of the ground squirrel. Cultivation of
the land has, on the other hand, in portions of the state improved the
food supply. The general tendency is for the squirrels to breed up on
42
THE GROUND SQUIRRELS OF CALIFORNIA. V2 GS)
uncultivated land where they are least molested through human agency,
and from this they spread out and invade nearby cultivated fields.
The process is most conspicuously in evidence during late summer con-
sequent upon the emigration of the young of the year, this beg in
compensation for the tendency to congestion of population brought on
during the breeding season.
Reduction in the food supply locally causes the squirrels to spread
out in search of new pastures. Such movements are usually less than
a mile in extent, and of course come particularly to notice in the vicinity
of grain fields and orchards to which the squirrels drift at the time the
crops begin to ripen. Some idea of the rate with which ground squirrels
reinfest cultivated fields which are adjacent to wild land may be had
from the following instance. Mr. O. N. Garrison of Karlimart, Tulare
County, stated in an interview that during the spring of 1918 thirty-six
ground squirrels were drowned out on a five-acre field of alfalfa at the
first irrigation and this in spite of the fact that the field had been free
from squirrels at the end of the previous irrigation season in the fall
Oro U7:
From the earliest times of which we have record to the present day
the California Ground Squirrels have given the impression of abun-
dance. Changes in the status of the species within history have only
concerned local occurrence. There is nothing to show that there has
been any extension of the general range of the species, or any retraction
in it either. As already set forth, the arrival of the white man and the
institution of agriculture has undoubtedly had the effect locally of
increasing the ground squirrel population. On the other hand, where
man has been aroused by the seriousness of their depredations to the
point of adopting and putting into force effective means of control the
numbers of the squirrels have been conspicuously reduced. Thus at
Earlimart on May 16, 1918, ground squirrel burrows were found to be
abundant over a large acreage of ‘‘hog wallow’’ land. Live squirrels,
however, were exceedingly scarce, only five being found on one tract of
forty acres which had been thoroughly poisoned the previous season.
A count taken on this tract showed that there was an average of fifty
empty burrows to each squirrel present.
A very few localities have been reported in which the squirrels are,
for the time being at least, things of the past; but the possibility of
re-invasion presents itself, and this, as already shown, may be a very
rapid process. It would seem that ground squirrels, like weeds or
scale bugs, will have to be watched continually, and proper measures
taken whenever necessary to prevent the reinfestation of land which is
thought to have been freed.
The difficulties in arriving at a fair estimate of the damage done by
the California Ground Squirrel, which is by far the most injurious
species in the state, are many and various. We have tried to get at
a satisfactory estimate (not a guess) in terms of dollars per annum,
but have not succeeded. It may be of some interest, however, to give
some other figures, indicative in partial degree of the loss that may be
occasioned by this ground squirrel.
In order to ascertain the bearing of squirrels upon grazing interests
we have found some basis for estimating squirrels in terms of live-
stock. We have weighed and examined the stomach contents of a series
43
636 THE MONTHLY BULLETIN.
of squirrels, with results already given. These, summarized, show that
one ounce of dry grain or seeds, or four ounces of green vegetation, 18
consumed each day by an average California Ground Squirrel. If we
take fifty pounds of green stuff as representing the amount of forage
consumed daily by one steer on open range, then 200 squirrels would
appropriate the forage which would keep one steer. Twenty squirrels
would eat as much as one sheep, and this last estimate would be most
significant, because sheep graze closer and hence the competition here
would be sharpest.
Expressing this relationship in another way, taking the average popu-
lation of ground squirrels on open range as one per acre or 640 per square
mile, the squirrels on each square mile appropriate the forage of three
steers or 32 sheep. If the entire range of the California Ground
Squirrel be taken into account and be supposed to consist purely of
erazing lands (and so of minimum land value) grazed to their fullest
capacity, then the squirrels of this species take the place of 160,000
cattle or 1,600,000 sheep. Of course, it is not likely that the squirrels
come into actual close competition with livestock in ordinary years; but
in extra dry years, such as that of 1917-18, when all the living things
which depend on vegetation for support are hard pressed to maintain
existence, then the squirrels cannot help but crowd the cattle interests
of the country, which are of such vital human importance.
‘FISHER GROUND SQUIRREL.
Citellus beecheyi fisheri (Merriam).
PLATE V.
Other names.—Fisher Spermophile; Digger Squirrel, part; Spermophilus beecheyi,
part; Spermophilus beecheyi fisheri; Spermophilus grammurus fisheri; Citellus
varicgatus fisheri; Citellus grammurus fisheri; Otospermophilus beecheyi fisheri;
Spermophilus grammurus beecheyi, part.
Field characters.—As for the Beechey Ground Squirrel, differing in paler tone of
general coloration, and in more extensive and purer white shoulder patches. Mength
of body alone about 93 inches, with tail about 6 inches more.
Description.—In all pelages: Closely like beecheyi, except for pallid tones of
color predominantly light cinnamon-drab, and extension of light areas. The shoulder
patches in typical fisheri are much clearer white and tend to meet on the fore back
between the shoulders; in some specimens the mid-dorsal grayish brown stripe is
almost obliterated by these white invasions. The back of the ear is usually grizzled
buffy in fisheri instead of chiefly black, and its hinder margin and base are silvery
white. The lower surface of the body and the upper surfaces of the feet are usually
much whiter, less buffy, than in beecheyi. ;
Color variations.—The range of individual and seasonal variation in fisheri seems
to be about the same as in beecheyi.
The extreme of the characters of fisheri are developed in the Inyo region, and grad-
ual intergradation or blending takes place towards beecheyi chiefly through southern
Tulare and Kern Counties. The dotted line on the map (fig. 17) separating the ranges
of fisheri and beecheyi represents no place of abrupt demarcation but only somewhere
near the middle of the belt of intergradation. Many individuals from the vicinity
of this hypothetical line are so nearly betwixt typical beecheyi and typical fisheri
that they can only arbitrarily be placed under one name or the other. This has been
done with such intermediate examples in the lists of specimens examined.
44
THE GROUND SQUIRRELS. OF CALIFORNIA. 637
Measurements.—Average and extreme measurements, in millimeters, of thirteen
mature specimens from Inyo County are as follows: Five males: total length, 417
(400-455) ; tail vertebre, 163 (155-180) ; hind foot, 57 (50-65); ear from crown,
19 (16-22); greatest length of skull, 55.4 (54.1-57.0) ; zygomatic breadth, 34.7
(33.38-36.3) ; interorbital width, 13.3 (13.1-13.9). Eight females: total length, 396
(374-417) ; tail vertebrae, 157 (145-170) ; hind foot, 53 (51-55); ear from crown,
19 (18-23); greatest length of skull, 53.9 (52.3-55.7); zygomatic breadth, 33.2
(31.0-34.7) ; interorbital width, 18.2 (12.2-14.3).
The above figures show that the race fisheri is decidedly smaller in almost every
particular than beecheyi. The disparity between the sexes is quite as well shown,
however, and the rest of the variable features seem to be exhibited in about the
same degree, making due allowances for the smaller number of fisheri measured.
Weights.—Average and extreme weights in grams cf eight mature specimens from
Inyo County are as follows: Five males, 589 (480-656); three females, 400
(321-440). Averages in ounces: males, about 202; females, about 14.
It is probable that a larger series of weights would give somewhat different averages.
That for the females seems low.
Type locality——kKern Valley, 25 miles above Kernville [=South Fork of Kern
River 25 miles east of Kernville], Kern County, California (Merriam, 18938, p. 183).
Distribution area.—Roughly the western borderlands of the Mohave Desert, north
into the Inyo region and south as far as the northwestern arm of the Colorado
Desert. More in detail, the western side of Owens Valley including the adjacent
east slopes of the Sierras north to the vicinity of Mammoth Pass: east from the south-
ern end of Owens Lake through the Coso, Argus and north end of the Panamint
Mountains; the extreme southern Sierras, including the entire drainage basin of the
Kern River; the southern end of the San Joaquin Valley south of Tulare Lake,
and the Carrizo Plains country and adjacent hills and valleys to the westward; the
Tehachapi, Tejon, San Bernardino, San Jacinto and Santa Rosa Mountains and
adjacent desert borders. The approximate line of blending between the races beecheyi
and fisheri is shown on the map (fig. 17). With regard to life-zone the Fisher Ground
Squirrel extends from the Lower Sonoran to the Canadian but its greatest numbe*s
are reached, and most of its habitat lies, in the Upper Sonoran (see fig. 23).
Specimens examined.—A total of 96 specimens from the following localities, all
in California: Inyo County: Little Onion Valley, 7,500 ft., east slope Sierra Nevada
west of Independence, 1; Independence, 4; vicinity of Lone Pine, 3; vicinity of Jack-
ass Spring, 6,200-6,500 ft., northern part of Panamint Mts., 9; Little Lake, 2;
Olancha, 1; Little Cottonwood Creek, at 10,000 ft. alt., 1. Tulare County: Jordan
Hot Springs, 6,700 ft., 1; Jackass Meadow, 7,750 ft., 1; Trout Creek 6,000 ft., 3;
Taylor Meadow, 7,000 ft., 5; Cannell Meadow, 7,000 ft., 1; Earlimart, 2; Tipton, 5.
Kern County: Kern River, seven miles above Kernville, 1; Fay Creek, 4,100 ft., 2;
west slope Walker Pass, 4,600 ft., 3; Weldon, 1; Isabella, 2; Bodfish, 1; Kern River,
twelve miles below Bodfish, 1; eight miles northeast Bakersfield, 1; San Emigdio, 2;
Fort Tejon, 5. San Luis Obispo County: near Simmler, on Carrizo Plains, 1. Ven-
tura County: Mount Pinos, 8. San Bernardino County: Victorville, 2; Cushenbury
Springs, 1; Doble, 7,000 ft., San Bernardino Mts., 1; Bluff Lake, 7,500 ft., San
Bernardino Mts., 2; F*sh Creek, 6,500 ft., San Bernardino Mts., 1. Riverside
County; near Banning, 1; Cabezon, 9; Snow Creek, near Whitewater, 1; Schain’s
Ranch, 4,900 ft., San Jacinto Mts., 4; Fuller’s Mill, 5,900 ft., San Jacinto Mts., 1;
Round Valley, 9,000 ft., San Jacinto Mts., 1; Tahquitz Valley, 8,000 ft., San Jacinto
Mts., 1; Strawberry Valley, 6,000 ft., San Jacinto Mts., 9.
The Fisher Ground Squirrel is closely related to, and -in general
very much like, the California Ground Squirrel with which it blends
in Kern and Tulare Counties. In general appearance the former is
slightly smaller and decidedly paler than the latter. The Fisher Squir-
rel may be recognized in the field by its extensive white shoulder
patches. This sub-species is also known as “‘digger’’ squirrel.
The range of the Fisher Squirrel includes Kern Valley and part of
Owens Valley, the extreme southern part of the San Joaquin Valley,
and a strip of territory alcng the northern and western edges of the
” 45
638 THE MONTHLY BULLETIN.
Mohave Desert from the mountains east of Owens Lake south to the
Santa Rosa Mountains west of Salton Sea.
In altitude this squirrel ranges from 450 feet, as at Palm Springs
at the eastern base of San Jacinto Peak, to 10,500 feet, as within a
quarter of a mile of the summit of the same mountain (H. S. Swarth,
MS). It is to be found from the southernmost plains of the San
Giellus beecheys beechey!
Giellus beechey/ fisheri
Cilellus beechey! Nesiolicus
Citellus douglas Wi
Cilellus varie galus grammurus
DISTRIBUTION MAP
MUSEUM OF VERTEBRATE ZOOLOGY
UNIVERSITY OF CALIFORNIA
Fic. 17. Map showing California distribution of the California, Fisher, Catalina
Island and Douglas ground squirrels, and the Rock Squirrel, all being of the “digger”
category. ‘The spots represent localities from which actual specimens have been
examined.
Joaquin Valley to 10,000 feet altitude in the Mount Whitney region.
This rodent thus shows little regard for zonal limitations, occurring all.
the way from the Lower Sonoran zone to the Canadian zone, though
its numbers above the Upper Sonoran are small. It is equally at home
46
=
THE GROUND SQUIRRELS OF CALIFORNIA. 639
in the cultivated fields in the irrigated sections, about Bakersfield and on
the rocky ridges of the Panamint Mountains.
At Jackass Springs, in the Panamint Mountains, Inyo County, on
October 5, 1918, eight Fisher Ground Squirrels were counted in a three-
hour census in the belt of sagebrush and pifion. These were invariably
perched upright on the summits of gray granite boulders. They were
even then notably pale-colored, with beccheyi in mind (J. Grin-
nell, MS).
At Mount Pinos, Ventura County, during the first week in July,
1904, Fisher Squirrels were present from the very summit (8,826 feet)
down. They were trapped among the rockpiles near the top, and on
the smooth slopes among the firs on the north side. Young were num-
erous, and quite unsuspicious, being run down with ease when caught
a little ways from their retreats (J. Grinnell, MS).
Near Lone Pine in Owens Valley on June 16, 1917, Fisher Ground
Squirrels were found inhabiting the lower embankment of the Los
Angeles Aqueduct. At one point three miles south of Lone Pine, some
thirty squirrels were noted along the aqueduct in a distance of half a
mile. Other colonies were found along Lone Pine Creek at the edge
of an old orchard (A. C. Shelton, MS).
In the region about Bakersfield Fisher Squirrels were found in con-
siderable numbers near the mouth of Caliente Creek east of Bakersfield
both in the wheat fields and on the adjoining plains covered with a low
growth of cactus. In the irrigated region southwest of that city the
squirrels were locally numerous on pasture land.
The Fisher Ground Squirrel as far as we can see is indistinguishable
from the California Ground Squirrel in many particulars such as
behavior, voice and mannerisms. This statement applies also to the
general feeding and breeding habits of the form. Many incidents
bearing on such points as enemies and natural checks have been
recounted in our chapter relating to beecheyt, since they are for the
most part identical in the two races.
Certain instances of behavior in the desert race seem worthy of
special mention. At Isabella, Kern County, on July 4, 1911, W. P.
Taylor (MS) states that it was a common thing to see the squirrels up
from the ground in guatemotes or willows. At Palm Springs, River-
side County, on February 4, 1916, two Fisher Squirrels were seen to
leap an irrigation ditch near town, a clear jump of about four feet
(H. S. Swarth, MS). Sometimes individuals of this species do not
hesitate to jump into water and swim, so as to escape from enemies.
At Onyx, Kern County, on June 19, 1911, a half-grown squirrel was
surprised on the bank of an irrigation ditch which was full of water.
The stream was six feet wide, with rapid current. Without the least
hesitation, the squirrel precipitated itself into the water and swam
across, reaching the opposite shore by a diagonal down-stream course.
It then quickly ran to a burrow, with the location of which it seemed
familiar and from which it is likely to have come originally and crossed
the ditch of its own accord for the purpose of foraging (J. Grin-
nell, MS).
The time of birth of the young in this species varies with altitude,
more precisely zone, from April to late in June. At Cabezon, River-
side County, a one-third grown young one was secured May 16, 1908,
47
640 THE MONTHLY BULLETIN.
while at 8,500 feet on Mount Pinos, Ventura County, a similar sized
young one was taken July 11, 1904. At the former locality three juve-
niles and an adult female were drowned out of one community burrow in ~
an almond orchard. This is probably about the minimum number in a
litter, as the average number of young in a litter appears to be only
slightly less than in the California Ground Squirrel. “‘The average
number ... of young at a birth . . . along the borders of the Mohave
Desert appears to be ...6or7’’ (C. H. Merriam, 1910, p. 4). At
Schain’s Ranch, San Jacinto Mountains, on June 18, 1908, a family of
eight young ground squirrels was observed aboveground at one time
at the mouth of a burrow (W. P. Taylor, MS).
Regarding food preferences of this sub-species a special feature has
been noted with extraordinary frequency, as follows. Many Fisher
Ground Squirrels are taken in meat-baited steel traps set for predatory
carnivores under circumstances which make it seem certain that they
were caught while trying to steal the bait. They have also been known
to eat woodrats and even other individuals of their own kind which
they have found dead in traps.
At Kelso Pass, Kern County, on July 8, 1911, two Fisher Ground
Squirrels came to drink at a seepage from a spring. One drank six
times, the fifth time for over two minutes, by count of seconds (J.
Grinnell, MS). ;
The following records of cheek-pouch contents establish some of the
sorts of food taken by this animal. At Taylor Meadow, Tulare County,
a squirrel was taken on July 25, 1911, with 88 seeds of a lupine
(Lupinus grayt) in its cheek-pouches. Another squirrel taken seven
miles above Kernville, Kern County, on June 26, 1911, was carrying
a seed of the Digger Pine (Pinus sabiniana); while a third squirrel
taken at Lone Pine, Inyo County, had gathered and placed in its cheek
pouches 118 seeds of Hncelia frutescens and 5 seeds of Hymenoclea
salsola. Pe
Squirrels of this subspecies were found doing a large amount of dam-
age to the almond crop at Cabezon, Riverside County, on May 16, 1908.
Here they were living right in the almond orchard, most of the inhabited
burrows being dug close to the roots of the trees. Other short, shallow
burrows were noted, but these were thought to be of use only for tem-
porary protection in case the animals were taken by surprise (C. H.
Richardson, MS).
In Antelope Valley, near Fairmont, Los Angeles County, on June 22,
1904, the authors found ground squirrels doing enormous damage to
almonds, climbing the trees and biting open the green fruit to take out
the pit and often leaving the hull in place on the tree. The pit was
frequently found to have been removed from a remarkably small hole
in the side or end of the shell.
At various points within the range of fisheri we have been told by old
residents that digger squirrels have only recently invaded the locality
and that a few years ago there were none where many squirrels are now
present. In many such cases the sudden increase in the number of
ground squirrels is evidently due not to invasion from without, but to
the breeding up, under favorable conditions, of the local stock of squir-
rels which have been present all the time, but which was formerly so
48
THE GROUND SQUIRRELS OF CALIFORNIA. 641
small and scattered that it did not attract attention. A typical example
is as follows.
Residents of Owens Valley at Lone Pine stated in June, 1917, that
the ground squirrels there had only recently invaded the valley and that
none were known in that vicinity five years before. But from this same
locality specimens now preserved in the Field Museum of Natural His-
tory in Chicago were obtained in 1902, fifteen years previously.
Although the squirrels are said to be steadily increasing along the west
side of Owens Valley, little or no effort appears to have been attempted
at controlling the pest.
At the Car] Walters Ranch, two miles north of Independence, on
June 26, 1917, Fisher Ground Squirrels were found to be fairly abun-
dant on both this and most of the other ranches in the vicinity. They
had been considered a nuisance here for a number of years (A. C.
Shelton, MS).
The irrigation and cultivation of extensive areas have resulted in a
greatly increased available food supply which has proven acceptable to
-the ground squirrel and has resulted in greatly increasing its popula-
tion. It is the authors’ belief that the squirrels have been present in
Owens Valley from time immemorial and that as long as they were
few in numbers and stuck to the rocky, uncultivated ground they
remained largely unnoticed, but that when they invaded irrigated
fields and became numerous they attracted attention and were then
thought to have but just moved into the valley.
It is believed that, on the whole, there are only about half as many
Fisher Ground Squirrels to the square mile throughout its range as
there are California Ground Squirrels to the same unit of area in the
range of that form. Fisher Squirrels nevertheless prove very destruc-
tive locally to cultivated crops. Many small isolated orchards and
‘“dry-farmed’’ grain fields are scattered throughout the western and
northern parts of the range of fisheri and these frontier ranches are
the ones which suffer. While the money value of the crop destroyed
may be small, yet such crops are often the settler’s principal means of
obtaining a livelihood and, although this may be humble indeed, its loss
is felt critically. It is the authors’ belief that the Fisher Ground
Squirrel ranks third, or next after the Oregon Ground Squirrel, in point
of economic importance in California.
CATALINA ISLAND GROUND SQUIRREL.
Citellus beecheyi nesioticus Elliot.
Other names.—Island Spermophile; Citellus nesioticus; Spermophilus beecheyi,
part.
Field characters.— As for the Beechey Ground Squirrel. Only to be distinguished
from it on comparison of series of specimens; coloration averaging darker, general size
greater, and tail relatively shorter. Length of bod; alone, ‘n males, about 113
inches; w*th tail (without hairs) about 7% inches more.
Description.—Adulis in April: Similar to the Beechey Ground Squirrel (San
Francisco Bay region) as already described, but general coloration darker; top of
head from nose to nape, and broad area down middle of fore back between light
49
4— 43007
642 THE MONTHLY BULLETIN. ,
shoulder patches, deep cinnamon-brown, the hairs individually being black, tipped with
cinnamon; middle of back darker in tone than top of head; spot above upper eyelid
blackish; cheeks and sides of neck much darker in tone than in beecheyi; whitish
shoulder patches, restricted in exten*, dull and indistinct as compared with fisheri and
douglasii, even more so than in beecheyi. Under surface of body very dark in tone,
the hairs extensively grayish bister at bases and tipped with cinnamon buff. Tail
and feet colored as in beecheyt.
Color variations.—The type and one other specimen show a black patch on the
crown, due to lack of cinnamon hair-tippings; this, of course, is merely an individual
feature.
The May-taken series at hand shows various transition stages from winter to sum-
mer pelage. In most of the specimens the fore parts are in fresh harsh summer coat,
while the rump is still covered with the winter coat, showing underfur, and being
more or less worn and faded. The tail in some examples is markedly worn and faded,
with the usually resulting changes in color. In some specimens the hairs of the
tail show but two dark bands instead of three; but this variation occurs also in
other near-related races of ground squirrels. The two skins taken in February are in
full winter pelage, showing more or less underfur over the whole body and no signs
of molt.. The fore parts, as compared with the summer pelage, are less bright in
color tones, and the shoulder patches are even less distinctly whitish. Hinder upper
- surface and tail exactly as in beecheyi of same season.
Measurements.—Avyerage and extreme measurements, in millimeters, of nineteen
full-grown specimens from near Avalon, Catalina Island, are as follows: Seven
males: total length, 471 (447-495); tail vertebrae, 189 (175-200); hind foot,
59 (55-63); greatest length of skull, 60.2 (56.1-63.7) ; zygomatic breadth, 36.9
(33.8-39.2) ; interorbital width, 14.8 (13.3-15.9). Twelve females: total length, 444
(406-475) ; tail vertebra, 179 (161-194) ; hind foot, 56 (538-62) ; greatest length of
skull, 57.7 (54.0-62.4) ; zygomatic breadth, 35.9 (83.38-87.6) ; interorbital width,
14.3 (18.0-15.4).
Close examination of the series of skulls shows to us no character by which to
tell them from beecheyi or fisheri except for average greater size. ‘There is the
usual range of variation in proportions, due to age, this factor being judged from
degree of wear on the crowns of the molariform teeth. Old skulls are largest,
broadest relatively to length, and with most prominent ridges and processes. It is
difficult for us to understand how Hlliot (1904, p. 263) could have assigned the
numerous cranial characters he did to the form he named, except on the ground that
he examined but a very few specimens of beecheyi and fishert and that these
happened to be extreme.
Type locality.—Santa Catalina Island, California (Hlliot, 1904, p. 263); more
exactly, vicinity of Avalon, according to the collector of the type, Mr. John Rowley,
in interview.
Distribution area.—Santa Catalina Island, California. Life-zone, Upper Sonoran.
Specimens examined.—A total of 21 skins and skulls, all from the vicinity of
Avalon, Catalina Island. Two of these (including the type) were loaned us from the
Wield Museum of Natural History, Chicago; and nineteen were loaned us from
the Museum of History, Science and Art, Los Angeles.
Only three species of rodents are known to be native to Catalina
Island, a harvest mouse, a white-footed mouse, and the Catalina Island
Ground Squirrel. This last-named animal is, as in each of the other
cases, but slightly differentiated from its counterpart on the adjacent
mainland. With little doubt it differs no more from its near relative,
the Beechey Ground Squirrel, in general habits and traits, than it
does in structure.
Until the present year very little has been known of the Catalina
Island Ground Squirrel. In fact, the original characterization of the
race was so unsatisfactory as to leave doubts in the minds of some
students as to whether the island animals really differ at all from the
THE GROUND SQUIRRELS OF CALIFORNIA. 643
mainland ones. Fortunately for the present writers, our appeal to Mr.
Frank S. Daggett, Director of the Museum of History, Scienee and
Art, in Los Angeles, was promptly met by action, and Mr. L. E. Wyman
of Mr. Daggett’s staff was detailed to go to Catalina and obtain a suffi-
cient number of specimens for deciding the doubtful questions. Mr.
Wyman was eminently successful, and the resulting series of skins and
skulls, together with the accompanying information, was freely placed
at our disposal for use in connection with the present paper.
Mr. Wyman found the squirrels fairly swarming May 9 to 16, 1918,
at the upper end of a narrow tract of bottom land about a mile back
of Avalon. This tract, dotted with elderberry trees, had been seeded
to barley, and the grain stood knee-deep except in the spots where it
had been persistently eaten down by the squirrels. The hillside adjoin-
ing. on the northwest was steep and fairly well covered with cactus and
chaparral, and in places it was honeycombed with burrows. The bottom
of the hill was beset with extensive diggings every fifty feet or so.
Besides the barley, the squirrels were feeding on a variety of wild
vegetation. Hach of the numerous stomachs examined contained.a well-
chewed green mass. Cheek-pouches were found to contain barley blades’
and certain seeds, and in one ease four bulbs of ‘‘sour-grass’’ or ‘‘ grass-
nuts’’ (Brodiwa capitata), the largest of which was half an inch in
greatest diameter. These bulbs seem to be specially sought after, as
several small areas were found, usually on south-fronting grassy hill-
sides, where the ground was all dug up by the animals, and hulls of
Brodiza bulbs were lying about.
One ground squirrel was seen at work in a wild tobacco tree about
seven feet from the ground. He had gnawed at the stem near the top
until only a shred kept it from dropping. Gnawed shells of chilicothe
seeds were also found.
Mr. Wyman believes that the notes and actions of the Catalina
Island Ground Squirrel do not differ to any appreciable extent from
those of the mainland Beechey. The island animals were perhaps
slightly less noisy, though when once started to barking they seemed
hardly able to stop. They were found to be shy on open ground,
hustling to cover when the invader of their domain was yet 200 yards
off. By sitting quietly under a tree, however, Mr. Wyman had one
squirrel approach him to within ten yards and feed on barley shoots.
On the brushy hillsides, the collector was able to stalk his quarry with
ease.
All the females taken were notably fat, and none contained embryos.
Also no young of the year were seen; so that it would seem that the
breeding season of the island squirrel is much later than that of the
mainland animal—later, at least, than May 16. Every specimen taken
by Mr. Wyman was ‘‘loaded with fleas;’’ these, however, quickly dis-
appeared and in no ease caused any annoyance to the collector.
Since ground squirrels were seen by the senior author commonly in
August, 1903, in the vicinity of the Isthmus, near the northwest end
of Catalina, it may be inferred that the animals are widely distributed
over this island. No species of ground squirrel whatever exists native
on any of the other California islands.
51
644 THE MONTHLY BULLETIN.
DOUGLAS GROUND SQUIRREL.
Citellus douglasii (Richardson).
PLATE Il.
Other names.—Douglas Spermophile; Digger Squirrel, part; Arctomys douglasii ;
Citellus douglasii; Citellus variegatus douglasii; Spermophilus grammurus douglasii ;
Spermophilus douglasii; Citellus beecheyi douglasii; Spermophilus grammurus
beecheyi, part; Citellus grammurus douglasii.
Field characters.—As for the Beechey Ground Squirrel, from which differs notice-
ably in the possession of a blackish brown wedge-shaped patch on the fore part
of the back; also shoulders more extensively silvery white, and tail longer. Length
of body alone, in males about 11 inches, with tail about 8 inches more.
Description.—Adults in early summer pelage: Crown of head to nose buckthorn
brown, becoming mixed with blackish toward eyes and ears; backs of ears deep bister
brown margined behind broadly with clay color; insides of ears dull cinnamon-buff ;
eyelids white; whiskers black; side of head and of body behind shoulder deep bister
brown, with much buffy white tippings to hairs; a conspicuous wedge-shaped patch
on middle of fore part of back, with apex at nape of neck, solid deep bister brown
in color, almost black in some specimens; shoulder patch extensively silvery white,
this extending backwards to hinder end of median dark wedge. Minder portion of
body colored as in the Beechey Ground Squirrel, but dappling more conspicuous, due
to the whiter tone of the light spots. Under surface of body of darker tone than in
beecheyi, seemingly due to the darker, sepia brown, bases of the hairs showing
through the dull white or buffy overwash. Feet as in beecheyi but clouded above with
dusky. Tail colored as in beecheyi but light tippings to hairs greater in extent and
whiter in tone, thus accentuating the white fringe, and producing a grayer effect
throughout.
Color variations.—Young but a third grown usually show the characters of the
species, both as to color and relative tail length, quite as well as do adults. In one
example, however, the black dorsal wedge is considerably obscured by buffy mottlings,
and it thus resembles beecheyi of the same age.
The effects of wear and fading rarely bring such extreme modification of color tones
in douglasiti as in beecheyi and fisheri, possibly due to the lesser intensity of the
sunlight and dryness to which their habitat is usually subject. The black wedge on
the fore back is most vivid in fresh pelage; in cases where wear and fading have
progressed to an extreme degree, the black wedge is much dulled toward brown, and
may be effaced almost entirely. The identity of the ground squirrels in any given
locality can be determined with certainty by securing several individuals, when the
normal, distinctive coloration is sure to be shown by some of them.
Measurements.—Average and extreme measurements, in millimeters, of seventeen
full-grown specimens from the northwestern counties of California (Sonoma to
Humboldt) are as follows: Twelve males: total length, 478 (488-504) ; tail vertebre,
200 (175-221) ; hind foot, 60 (57-63) ; ear from crown, 23 (19-29) ; greatest length
of skull, 60.5 (57.8-63.1) ; zygomatic breadth, 37.0 (34.9-88.2) ; interorbital width,
14.38 (18.5-15.7). Five females: total length, 489 (427-453); tail vertebrae, 192
(161-210) ; hind foot, 57 (56-60) ; ear from crown, 23 (18—26) ; greatest length of
skull, 58.5 (56.8-60.4) ; zygomatic breadth, 35.9 (35.0-86.8) ; interorbital width, 14.0
(138.1-15.0).
Always taking age into account, there appear to be fairly diagnostic average skull
characters for douglasii as compared with beecheyi, fisheri and nesioticus. Douglasii
averages smaller in regard to auditory bulle, and narrower as regards rostrum and
brainease. Yet, as the above measurements show, the gross size of the skull is not
especially different. :
Type locality.—Probably somewhere in southern Oregon or northern California.
The type was a hunter’s skin “received from the banks of the Columbia” (Richardson,
1829, p. 172). :
Distribution area in Californiaw—Roughly, the northwestern section of the
state, north of San Francisco Bay, west of the lower Sacramento River, and north of
a diagonal line from near Chico northeast to the Nevada line near the southern
52
STATE COMMISSION OF HORTICULTURE PLATE II
OREGON, GROUND SQUIRREL (AT LEFT); DOUGLAS GROUND SQUIRREL (AT RIGHT),
THE GROUND SQUIRRELS OF CALIFORNIA. 645
boundary of Modoc County. (See map, fig. 17.) Life-zone, Upper Sonoran and
Transition, ranging down into Lower Sonoran along the western side of the Sacra-
mento Valley. Altitudinally, the species ranges from near sea level up to as high as
6,500 feet (near South Yolla Bolly Mountain) and even 6,800 feet (on- the Scott
Mountains, Siskiyou County).
More in detail: The southern limit of the range of douglasii is not known to reach
the Golden Gate; it falls, on the sea-coast, somewhere not far to the north of Point
Reyes Station, and extends from there to the vicinity of Petaluma, leaving the south-
ern two-thirds of Marin County uninhabited. It extends nearly or quite to Benicia
and to the southern end of the range of hills west of Vacaville. The flood-plain of
the Sacramento River forms the eastern boundary north to beyond the Marysville
Buttes. Thence northeastward, across the Sacramento Valley, there is no obvious
barrier. In Butte, Plumas and Lassen Counties the ranges of douglasii and beecheyi
approach very closely, but so far as known they do not overlap; nor have undoubted
hybrids or geographic intergrades been reported.
_ Specimens examined.—A total of 65, from the following localities in California:
Modoc County: Sugar Hill, 3; Parker Creek, Warner Mts., 3; Deep Creek, Warner
Mts., 1. Siskiyou County: Mayten, 1; six miles northwest of Callahan, Scott River
Valley, 6; Summerville, 1; Castle Lake, 3. Shasta County: McCloud River, near
Baird, 7. Tehama County: Mill Creek, 2 miles northeast of Tehama, 4; four miles
south of South Yolla Bolly Mountain, 1. Butte County: four miles southeast of
Chico, 4; Dry Creek, on Oroville-Chico road, 3. Glenn County: Winslow, 4. Yolo
County: Rumsey, 1. Solano County: three miles west of Vacaville, 2. Humboldt
County : Eureka, 1; Fair Oaks, 2; Ferndale, 1; Cuddeback, 1. Trinity County: Hay-
fork, 2; Helena, 2. Mendocino County: Sherwood, 3; three miles south of Covelo, 1;
six miles north of Willets, 1; Mount Sanhedrin, 8. Sonoma County: seven miles west
of Cazadero, 4.
The Douglas Ground Squirrel belongs to the group of large, bushy-
tailed, tall-eared ground squirrels which include the California, Fisher,
Catalina Island and Rock Squirrels, and in common with the first and
second of these at least it is often called Digger Squirrel. Although
the differences are not great, they are evident and should be recognized
in economic work, for they not only concern color, but apparently also
habitat and food preferences. The Douglas Squirrel differs from its
next neighbor of the ‘‘digger’’ category, the California, in having a
conspicuous blackish wedge-shaped patch on the middle of the back
between the shoulders, in having the shoulder region more extensively
grayish white, and in having the tail a little longer and grayer.
The name of the squirrel now under discussion was bestowed upon it
(Richardson, 1829, p. 172) in acknowledgment to an early English
explorer in western America, David Douglas, for having brought home
specimens of the animals met with, many of which proved to be new
to science. Douglas’s travels carried him through parts of Oregon
and probably northern California; but the type of this ground squirrel
was a hunter’s skin received from the Columbia River. There is no
tellmg now exactly where it really came from originally, though prob-
ably from much south of the Columbia, since the species is not known
to have existed within history that far north.
In northern California the Douglas Ground Squirrel occupies a wide
area; in fact, at the extreme north from the Pacific Ocean to the Nevada
line. To the southward its range includes all of the upper Sacramento
Valley, and its western half lower down, and the whole coast region
(hills and included valleys) south nearly to San Francisco Bay. Refer-
ence to the map (fig. 17) will show that the range of the Douglas is
almost exactly complementary to that of the Beechey; at no point do
53
646 THE MONTHLY BULLETIN.
they overlap, or, indeed, as far as known, quite meet. Roughly, the
Douglas Ground Squirrel occupies the northern and northwestern third
of the state.
The local or habitat preference of this species is more exclusively
for hilly country than in the case of the California Ground Squirrel.
It is true that the Douglas exists out on the floor of the Sacramento
Valley nearly to the lands annually flooded along the river; but it
occurs there interruptedly, in far separated *‘colonies,’’ and never any-
where are the great numbers reached that characterize beecheyi in the
San Joaquin Valley. The preferred haunts of dowglasw are the open-
ings or glades on hillsides, beneath scattered oaks or pimes, or else the
open tracts along stream courses, not, however, quite down to the
water’s edge. The edges of the smaller valleys between the coast ranges
are well populated, but the open floors of these valleys are not often
invaded very far or in any considerable numbers. Dense chaparral
and thick woods are avoided altogether.
It is interesting to note here that where the coast redwoods have been
lumbered out the Douglas Ground Squirrels have come in from the
interior so as to be plentiful where formerly scarce or wanting. Chapar-
ral slopes which have been swept by fire are also quickly invaded and
occupied for a time, until the brush grows up thickly again. It is
probable that the squirrels are unable to maintain themselves against
enemies, such as bobcats, that habitually hunt by stealth through under-
brush; the squirrels require a certain amount of space around them so
that they can have a fair show of reaching the safety of their burrows
after an enemy is first caught sight of. Even though the Douglas
Ground Squirrels are nowhere so very numerous as compared with
certain other rodents, their predilection for clearings brings them into
economic prominence locally. We have been told repeatedly of cases
where newly cleared farms in mountain valleys have been invaded at
harvest time from the nearby hillsides, to the almost complete loss
of the crops.
It is a curious thing that the Douglas Ground Squirrel should not
oecur south clear to the shores of San Francisco Bay, inasmuch as the
Beechey on the south side of the bay extends up to either the very
shore line itself or to the margin of the salt marshes adjacent, or did so
until very recent years This may be merely another indication of the
lesser degree of aggressiveness or prolificness on the part of the Doug-
las Squirrel. Marin County seems to be devoid of any ground squirrels
whatsoever, except for a few douglas along.the Sonoma County bor-
der. Joseph Maillard (interviewed on May 8, 1918) states that in his
forty years or more of residence in Marin County, he never saw any
ground squirrels in the southern part or westwardly towards Point
Reyes. Individuals were seen twice many years ago on the Rancho San
Geronimo, but “‘they never stayed.’’ ‘To all appearances the conditions
here are identical with those in the Russian River district and a few
miles west of Petaluma where the animals in question are plentiful,
or used to be until successfully combated.
Within the California portion of its range the Douglas Ground Squir-
rels are believed to be most numerous in Tehama County, this according
to the consensus of opinion in the office of the State Superintendent of
Rodent Control. In Shasta County, next on the north, there are rela-
54
THE GROUND SQUIRRELS OF CALIFORNIA. 647
tively few. To the westward they extend within a mile of the seacoast
in the vicinity of Eureka and at Cape Mendocino, but elsewhere mostly
not closer to the sea than eight or ten miles. Nowhere in the immediate
coast belt are they reported especially numerous or injurious. Pocket
gophers there loom up as the most destructive rodent.
The voice and mannerisms of the Douglas Ground Squirrel are not
to us in any points that can be remembered materially different from
those of the California Ground Squirrel. A fair test of this could, of
course, only be made upon the two if studied side by side under per-
fectly normal conditions. In the nature of the case this is impossible,
for in no known locality do they occupy common ground.
The tail is at all times the most conspicuous feature of this ground
squirrel. Sometimes when running to its burrow a squirrel will hold
its tail in a continuously vertical position, or this member may be
thrashed fore and aft. Ordinarily the tail is held nearly parallel to
the ground, with more or less of an arch in it. In this posture of tail
one is reminded strongly of the Gray Squirrel.
Our own observations, and the testimony of people in general who
are familiar with several of our ground squirrels including the Douglas,
indicate that the latter is the most prone of all to climb trees. For
instance, near Tehama, June 8, 1912, several individuals were seen
well up in large white oaks (W. P. Taylor, MS). At Winslow, Glenn
County, June 19, 1912, one was seen in a buckeye, and several from
twelve to fifteen feet above the ground in willows and cottonwoods
(W. P. Taylor, MS). At Sisson, Siskiyou County, August 11, 1914,
one was seen thirty feet above the ground in an incense cedar (T. I.
Storer, MS). It is a common thing to see them perched upon the
tops of fence posts or stumps. Individuals may under certain circum-
stances so nearly resemble Gray Squirrels as to be actually mistaken
. for them. This emphasis of the tree-climbing habit in the Douglas
Ground Squirrel is, suggestively enough, thus associated with greater
length of tail and grayer tone of color of tail, as compared with its
nearest relatives. It seems, also, that this species, more generally than
any other, raids orchard trees such as almond and apricot.
The sure test, on the basis of behavior, of a ground squirrel as com-
pared with any true tree squirrel, such as the California Gray, is that
the former, no matter how high in a tree when discovered, will, upon
alarm, take to the ground as quickly as possible, and seek safety in a
burrow below ground, rather than make off through the branches from
tree to tree, or ascend into the uppermost foliage of a treetop. Not
infrequently, when surprised in a tree, a ground squirrel will for the
time being ‘‘freeze’’ and attempt to escape being seen by remaining
motionless. But after being further disturbed and once starting, he
makes for the ground by the shortest route.
The burrowing habits of the Douglas Squirrel are similar to those
of related species. Steep banks seem to be chosen for burrowing into,
whenever available. Many burrows open under rocks, bushes and
tree roots. On open, level ground, with no protective shelter at hand,
the mouths of the burrows are marked by good-sized mounds, showing
the presence of an extensive system below ground. As far as we know,
no one has yet made a complete excavation of the burrow system of
this species.
5b
648 THE MONTHLY BULLETIN.
The breeding season is indicated by the time of appearance of the
young aboveground. In Scott Valley, Siskiyou County, where the
species is abundant, very small young were seen abroad on June 8
(1911). At Winslow, Glenn County, young one-fourth to one-half
erown were captured on June 16 (1912). At 6,800 feet altitude on the
Saloon Creek Divide, in the Scott Mountains, Siskiyou County, July
10 (1911), nursing females were captured, but no young were yet out
(L. Kellogg, MS). It is thus probable that at the lower altitudes the
young are born during the last half of May, while at the highest levels
they are not born until at least a month later. Only one litter is reared
each year.
Unfortunately we have no facts of our own to offer in regard to
size of litter. We have an idea that fewer young are born each year
than in the case of the California Ground Squirrel, judging roughly
from the numbers of young seen aboveground, about five. But this is
almost pure conjecture. F. E. Garlough, of the Uniied States Bio-
logical Survey, is under the impression (interviewed September 7,
1918) that litters in the lowlands average close to eight, while in. the
mountains five is the usual number. He has known of as few as two
and as many as fourteen embryos having been found in pregnant
females.
The following definite data on file in the Museum of Vertebrate
Zoology show some of the kinds of food selected by the Douglas Ground
Squirrel and also the quantity in which each of these kinds may be
gathered at one time. A male squirrel taken on Dry Creek where
-erossed by the Oroville-Chico road, in Butte County, May 31, 1912,
contained in its cheek pouches 29 seeds of a wild lupine (Lupinus
micranthus). Three others taken on Butte Creek, near Chico, June 3
and 5, 1912, contained in their cheek pouches materials as follows:
male, 12 seeds of milk thistle (Silybwm marianwm) ; female, 219 grains
of barley and one head of English plantain (Plantago lanceolata) ;
female, 142 grains of barley. The cheek-pouch contents of two squirrels
taken on Mill Creek, near Tehama, June 12, 1912, consisted of, respec-
tively : female, 121 seeds of bur clover (Medicago hispida) and 70 small
unidentified seeds, part loose and part in three whole pods; female, 181
seeds of brome-grass (Bromus carinatus) and one piece of an acorn.
Two squirrels taken in the hills three miles west of Vacaville, July 3
and 6, 1912, contained in their cheek-pouches: female, 29 seeds of Napa
thistle (Centaurea melitensis) and 80 seeds of bur clover; male, 82
seeds of bur clover, 4 seeds of Napa thistle and one cherry pit. A
male taken three miles south of Covelo, Mendocino County, July 20,
1913, held in its cheek-pouches 14 whole fruits and 103 separate seeds
of the common manzanita (Arctostaphylos manzanita), as also a few
small unidentified seeds of two kinds.
From all sources comes the testimony that this species takes barley
and wheat with particular avidity. Its storage propensities are highly
developed, and it would be interesting to see actual figures as to the
quantity of grain garnered underground in one autumn season. Where
they invade apricot orchards, as in the foothill district of the Warner
Mountains near Alturas, these squirrels climb the trees and take out
the pits, discarding the pulp of the fruit.
56
THE GROUND SQUIRRELS OF CALIFORNIA. 649
The Douglas, as is known of most other ground squirrels, is fond of
flesh when this can be obtained. Many have been taken in the meat-
baited steel traps kept out in various localities for carnivores.
Hibernation seems to be more prevalent with dowglasw than with
beecheyi, for all of the population of the former is reported to disappear
for weeks at a time, even in the lower valleys. At the higher altitudes,
where there is more or less heavy snow, all the squirrels disappear over
a period of some months. In Hayfork Valley, Trinity County, the
senior author was assured by several different people living there that
the Douglas Squirrels hibernate regularly and completely ‘‘ from Novem-
ber till April.’’ The earliest spring record we have for a mountainous
region is of one squirrel caught in a box trap February 25 (1911) near
Helena, Trinity County (A. M. Alexander, MS).
The natural enemies of this squirrel probably include practically all
those already specified in our chapter on the California Ground Squir-
rel. Only one specific instance is at hand. A gopher snake found
run over in a road near Chico, June 7, 1912, was found to contain in its
stomach a young Douglas Ground Squirrel (T. I. Storer, MS).
Coyotes are locally reputed to levy considerable toll upon this rodent.
We have heard the argument advanced against the poisoning of ground |
squirrels on wild mountain land in the northwest coast district that
reducing the squirrel population will deprive the coyote of one of his
chief sources of subsistence and that he will thereupon be forced to
seek food elsewhere and so be more prone to raid the poultry of the
valley ranches and the flocks of sheep in the mountains. On the other
hand, it may be advanced that the total coyote population is adjusted
to the total amount of food available at the season of least supply, and
that removal of any one important kind of food will in course of time
reduce the total coyote population able to exist in any general territory.
A high natural mortality for this species may account for its relative
_ lack of aggressiveness as compared with the California Ground Squirrel.
The testimony of a number of people from localities widely scattered
over the range of the Douglas Ground Squirrel is to the effect that
every few years there is a great reduction in its numbers. Some fairly
close observers, forest rangers in the Trinity region, for instance, think
this is due to the effects of severe winter weather, as when there is an
exceptionally heavy snowfall or torrential rains of unusual amount.
In either case the squirrels are thought to be drowned in large propor-
tion when lying dormant underground. Other persons think there are
recurrent epidemics of some disease fatal to the ground squirrels. We
have no-good evidence bearing upon either hypothesis.
Because of this observed reduction in numbers during some winters,
certain ranchers have objected to carrying on poisoning operations in
the fall, since their efforts might prove to have been unnecessary.
They prefer to deal with the naturally reduced squirrel population of
the springtime, at the close of the dormant period.
The general range of the Douglas Ground Squirrel has not changed
within history as far as definite records show. But, locally, there have
been marked fluctuations. On the western side of the Sacramento
Valley the animals have been almost completely cleaned out on many
large tracts as a result of systematic poisoning. This is particularly
true, as we are assured by W. C. Jacobsen, State Superintendent of
57
650 THE MONTHLY BULLETIN.
Rodent Control, of the Davis, Williams, Willows and Orland districts.
The reason for this is twofold: The Douglas Squirrels never did have
a secure foothold in the Sacramento Valley, such as the Beechey Squir-
rels have in the San Joaquin Valley; and the former, according to
current impression, takes the poisoned grain more readily.
On the other hand, with the clearing of forest lands in the coast dis-
trict, through lumbering and homesteading, the squirrels are thought
to have extended their confines locally. At any rate, they have become
numerous where formerly absent altogether or present in such small
numbers as to have been overlooked by the average person.
In certain sequestered valleys among the northern coast ranges we
have been assured of a loss to grain crops, where no effort at poisoning
the squirrels had been made, of from 5 to 25 per cent. In such cases
the squirrel population from the wild land immediately adjacent seemed
to have moved in en masse, as harvest time approached, to take advan-
tage of the special food supply thus made available. Nevertheless, the
Douglas Ground Squirrel, by reason of its relatively sparse population
over most of its range, and the ease with which it can be reduced in
numbers with reasonable effort, does not rank as of so much economic
importance as some other species. We would place it fourth among
our ground squirrels, giving precedence to the California, Oregon
and Fisher.
ROCK SQUIRREL.
Citellus variegatus grammurus (Say).
Other names.—Plateau Ground Squirrel; Rocky Mountain Ground Squirrel;
Citellus grammurus.
Field characters.—As for the Beechey Ground Squirrel, differing in longer tail and
erayer general coloration; fore parts of body continuously grayish white, without
specially set-off shoulder patches. Length of body alone about 104 inches, with tail
about 8 inches more.
Description.—Summer pelage: Head dull buckthorn brown, grizzled on cheeks and
sides of snout; eyelids dull white; whiskers black; backs of ears dull buffy brown,
insides of ears pinkish buff. Forward half of upper surface of body light gray, with
decided dusky mottling in transverse trend; hinder half of upper surface, of a tawny- —
olive tone, lighter on sides, and with similar transverse mottling. Whole lower surface
of body and upper surfaces of feet, pale pinkish buff, nearly white in some specimens ;
belly with grayish bases of hairs showing through. Tail considerably bushier than in
beecheyi, as well as being longer; length of hairs up to 50 mm. (2 inches) ; tips
of hairs more extensively white, thus nearly as in douglasii; dark and light intervals
on individual hairs same as in beecheyi, that is, three dark and four light, the latter
including the tipping.
Color variations.—Wear and exposure to intense sunshine evidently accounts for
the yellowing of the pelage of one specimen at hand; also the tail of the animal shows
a curious crinkling of the hairs as if scorched. An adult of date June 2 has the
forward half of the body in fresh new (summer) pelage; this is relatively harsh in
texture, without underfur. Young less than half grown are colored almost exactly as
described above for adults, but the pelage on the under surface is very scanty, so
that the bare skin shows through extensively. No winter specimens are at hand from
within the state of California.
Measurements.—Only two adult specimens are available from California. ‘These
are from the Providence Mountains, eastern San Bernardino County, and show meas-
58
THE GROUND SQUIRRELS OF CALIFORNIA. 651
urements, in millimeters, as follows: Male and female (nos. 117301 and 117800,
respectively, Biol. Surv. coll., U. S. Nat. Mus.) : Total] length, 470, 465; tail vertebree,
194, 205; hind foot, 58, 54; ear from crown, 20, 21; greatest length of skull, 61.2,
58.4; zygomatic breadth, 38.5, 37.0; interorbital width, 15.4, 14.2.
No skull differences of ciucial importance betweer grammurus and beecheyi are
apparent to us in the material at hand for study.
Type locality.—Purgatory River, near mouth of Chacuaco Creek, Las Animas
County, Colorado (according to Cary, 1911, p. 87). This form was originally
described by Thomas Say in 1823.
Distribution (in California).—Inhabits the Providence Mountains, in eastern San
Bernardino County (see fig. 17) ; also “the canyons of the Colorado River” (Merriam,
1910, p. 2). lLife-zone chiefly Upper Sonoran.
Specimens examined from California—A total cf five, all collected by Frank
Stephens, June 1 to 3, 1902, in the Providence Mountains, 5,000 to 5,500 feet alti-
tude. These were loaned us from the Biological Survey collection, United States
National Museum.
The Rock Squirrel is really a very close relative of the Beechey
Ground Squirrel and its habits are doubtless closely similar. It is a
wide-ranging form through the southern Rocky Mountain region, sta-
tions of occurrence in southeastern California being merely far western
outposts. Two of the specimens from the Providence Mountains are
young less than half grown; these were taken on June 1, and indicate
a breeding date at about the same time of year as for other ground
squirrels in the upper Sonoran zone.
OREGON GROUND SQUIRREL.
Citellus oregonus (Merriam).
PLATE II.
Other names.—Oregon Spermophile ; Bull Dog; Prairie Dog, part; Gopher; Bobby ;
Sand Rat; Short-tail; Woodchuck; Belding Ground Squirrel, part; Picket-pin, part;
Spermophilus oregonus; Citellus beldingi, part; Spermophilus richardsont.
Field characters——A medium sized, short-tailed ground squirrel, of stocky build,
and of brownish gray coloration without special stripes or markings of any sort (see
fig. 20a). Length of body alone about 8% inches, with tail about 24 inches more.
Description.—Adult in slightly worn spring pelage: Whole upper surface of a
general drab tone of coloration, tinged with cream-buff along sides and with dull
cinnamon on top of head and down middle of back. There is usually a faint pattern
of fine dappling. Eyelids dull white; whiskers black; ears clothed with short hairs,
like top of head in color. Upper surfaces of feet tinged with warm buff; palms naked ;
soles naked except for sparse hairing forward from heel nearly to tubereles; claws
horn-color, dusky at bases. Tail full-haired, flattish, widest about one-fourth way
back from end; color on upper surface mostly like back, except for showing through
of the hazel bases of the hairs, and for black zone about end succeeded by a
buffy white fringe; under surface of tail bright cinnamon rufous, with a broad band
of black at end and continuing backwards a little ways along either side, and the
whole margined narrowly with buffy white. Under surface of body dull cream-buff,
paling on throat and inner sides of legs; much brownish lead-color of the hair-bases
shows through on abdomen.
Color variations.—As wear proceeds toward an extreme the whole coat Reconies
grayer, and the cream-buff tints tend to disappear by fading. Males usually remain
much less worn than females; otherwise we can see no differences in coloration
between the sexes. The material we have shows evidence of but one molt each year,
59
652 THE MONTHLY BULLETIN.
this beginning about July Ist; but we have no specimens of dates between August
and May. It is possible that there is an autumn molt leading into a distinct winter
coat. Small young are softer-pelaged than adults, but colored just the same.
Measurements.—Average and extreme measurements, in millimeters, of nineteen
mature specimens from northeastern California are as follows: Nine males: total
length, 275 (260-300); tail vertebre, 65 (56-80); hind foot, 42 (87-45); ear
from crown, 9 (7-11) ; greatest length of skull, 45.1 (44.2-46.5) ; zygomatic breadth,
29.1 (27.1-31.0) ; interorbital width, 10.4 (10.0-11.1). Ten females: total length,
280 (271-292) ; tail vertebree, 57 (47-68) ; hind foot, 48 (41-44) ; ear from crown,
7.5 (6-8); greatest length of skull, 45.7 (44.9-47.2) ; zygomatic breadth, 29.7
(29.1-80.4) ; interorbital width, 10.4 (9.7-10.9).
From the above figures it would seem that, in this ground squirrel, females are
larger than males, except for tail and ear. ‘There are chances, however, that measure-
ment of greater numbers would give somewhat different results. It must be kept in
mind that the figures taken from the freshly killed animals were supplied by
several different people, and method of securing each measurement undoubtedly varies
somewhat with the persons doing the measuring. Hven with the skulls, all measured
by the senior author of this paper, size clearly varies to some degree with age, and the
proportions present in our series, of animals of different ages, will naturally affect
the average.
Weights.—Average and extreme weights, in grams, of six full grown females are:
302 (267-365.8). This average in ounces is about 103. The heaviest example was
notably fat, the lightest, lean. Adipose tissue thus counts importantly in weight,
though probably also weight increases, as does size of skull, with age. The animals
would probably weigh most just prior to hibernation, as they are then fattest.
Type locality—Swan Lake Valley, Klamath Basin [Klamath County], Oregon
(Merriam, 1898, p. 69).
Distribution (in California).—Occupies the northeastern corner of the state,
comprising the counties of Modoc, Lassen, eastern Siskiyou, and a portion of Plumas
(see fig. 18). The metropolis of the species lies in the Upper Sonoran life-zone, but
the animals extend through Transition, and even enter the Canadian. In detail:
west from the Nevada line as far as the vicinity of Goose Nest Mountain, Siskiyou
County, and vicinity of Big Meadows, in extreme northern Plumas County; south
from the Oregon line to the last named locality and to the valley of Susan Creek,
in Lassen County. Altitudinally, this ground squirrel extends from as low as 3,300
feet, on the Pit River, up to 9,000 feet, on Warren Peak, Warner Mountains (Mus.
Vert. Zool.). i
Specimens examined.—A total of 51 from the following localities in California:
Modoe County: Sugar Hill, 4; Goose Lake near Davis Creek, 2; South Fork Pit
River near Alturas, 3; Warner Mts. (Parker Creek and Squaw Peak), 6. Siskiyou
County: near head of Little Shasta River, north of Goose Nest Mt., 1; Bull Meadow,
northeast of Goose Nest Mt., 1; seven miles south of Macdoel, 24; Grass Lake, 6.
Lassen County: Termo, 1; west end of Horse Lake, 1; fifteen miles west of West-
wood, 1. Plumas County: ten miles west of Big Meadows, 1.
The Oregon Ground Squirrel occurs in California only in the extreme
northeastern counties of the state; but it has a rather wide general
range which includes much of Oregon east of the Cascades, and parts of
northern Nevada. It is a Great Basin plateau species, and its range
ends to the westward in California rather abruptly in the vicinity of
Goose Nest Mountain (head of Little Shasta River and Grass Lake)
and in the Pit River Valley in the vicinity of Burney, Shasta County.
To the southward it extends to Big Meadows, in Plumas County a
little southeast of Mount Lassen, and to the valley of Susan River, in
Lassen County.
In most of the sagebrush territory thus bounded, the Oregon Ground
Squirrel is conspicuously abundant, more so, some people believe, than
any other species anywhere in this state. While not so large as the
60
THE GROUND SQUIRRELS OF CALIFORNIA. 653
Cifellus ore gonus
Cifellus beldingi
Cifellus mollis stephensi
Citelus mohavensis
citelus ftereticaudus fereticaudus
Citellus fereticaudus eremonomus
Citellus tereticaudus Chorus
DISTRIBUTION MAP
MUSEUM OF VERTEBRATE ZOOLOGY
UNIVERSITY OF CALIFORNIA
Fig. 18. Map showing California distribution of the Oregon, Belding, Stephens
Soft-haired, Mohave, Yuma Round-tailed, Death Valley Round-tailed and Palm Springs
Round-tailed ground squirrels. The spots represent localities from which actual speci-
mens have been examined.
Beechey Ground Squirrel individually, it exceeds that species in num-
bers. At any rate, it ranks highest in importance among rodent pests
within its domain.
The Oregon Ground Squirrel is an inhabitant chiefly of mountain
meadows and the borders of the bigger meadows of the valleys. It
does not care for marshy ground, and it avoids thick brush and rocky
slopes. Ina way, it is complementary in habitat to the Douglas Ground
Squirrel, which occurs in much of the same territory; rarely are the
two seen on common ground. It is obviously because of its preference
for grass land that the Oregon Ground Squirrel has come so seriously
61
654 THE MONTHLY BULLETIN.
into conflict with man’s interests. Extensive clearing of the sage-
brush and seeding of these clearings to grain and hay has doubtless
benefited the squirrels. Indeed, this is likely one of the factors that
accounts for their increase of late years as testified to by several of
the old-time residents whom we have interviewed.
In Butte Valley, Siskiyou County, the Oregon Ground Squirrels
are popularly known as ‘‘bull dogs,’’ in Modoe County as ““short-tails”’
(evidently as distinguished from the longer tailed Douglas Ground
Squirrel), and elsewhere, locally, as ‘‘bobbies,’’ “‘prairie dogs,’’
‘“oophers,’’ and ‘‘woodchucks.’’ The last three names, of course, are
misapplications of names properly belonging to quite different kinds of
rodents.
In the latter part of May, 1918, the senior author accompanied Mr.
W. C. Jacobsen, State Superintendent of Rodent Control, in a tour
through northeastern California for the particular purpose of studying
the Oregon Ground Squirrel. In traveling eastward from Shasta
Valley, we first encountered this species toward the head of the Little
Shasta River, on the Mills ranch at about 4,200 feet altitude. Here
we found a field of vetch to be riddled with the burrows and secured one
of the animals to verify this, the westernmost record station for the
species. At Bull Meadows, a little east of Goose Nest Mountain, the
squirrels were exceedingly numerous on the uncultivated open ground
among scattering lodgepole pines. Subsequently we found them plen-
tiful around the margins of Grass Lake, nearly as far west, but due
south of Goose Nest. But it was on the floor of Butte Valley, from
the vicinity of Bray north to Dorris, wherever there were open grass
lands, that the Oregon Ground Squirrels simply swarmed. The fol-
lowing observations made May 16, 1918, on a ranch seven miles south
of Macdoel, will give an idea of the abundance of the animals where
conditions are most favorable to them.
Taking a position at the right-angled intersection of two fences,
the observer counted the animals in the quarter-circle gaze thus
bounded and found that there were sixty-five squirrels in plain sight
within a distance of one hundred yards of him. This was about nine
o’elock in the forenoon of a bright day, when the squirrels were at
about the height of their daily activity aboveground. Young of the
year were included.
Again, three adjacent plots of pasture were paced off, thirty-nine
paces square, and the open burrows counted. In one plot there were
151, in the second 182, in the third 194, an average of 176. This, fig-
ured out, makes 560 open burrows to the acre! If we allot one adult
squirrel to each five openings, which our observations showed to be
about the proper ratio, there would be 112 adults to the acre, not
counting young. Figuring, further, this would make somewhat over
70,000 squirrels per square mile! This, however, would pertain only
in limited areas and to those pasture lands where little effort had yet
been. made to reduce the pests. The population of the sagebrush
plains and pine woods of Butte Valley would be much smaller. It is,
of course, the pasture lands and grainfields where the squirrels come
into chief conflict with man’s interests, and this is where they are most
abundant. Some further estimates in this connection are lkely to
prove worth while.
62
THE GROUND SQUIRRELS OF CALIFORNIA. 655
The average weight of six adult female Oregon Ground Squirrels
was found to be 302 grams (about 104 ounces). The full stomachs of
these six squirrels were found to give an average weight of 18.5 grams.
Subtracting the ascertained weight of the stomach itself (3.5 grams),
gives the weight of the contents, alone, representing doubtless one full
meal, as 15 grams, or one-twentieth the entire weight of the animal.
The stomach contents was in all cases a closely packed, slightly moist
(not watery) mass of finely chewed green stuff. This could not be
analyzed as to kinds of plants represented, but the squirrels were seen
to be feeding upon all sorts of vegetation, practically everything going
to make up the usual forage grazed from such lands by live stock.
Our observations led us to believe that, at the very least, two full
stomach-loads of greens were eaten by each squirrel each day, or 30
erams of forage. Of course this does not account for wastage, evidence
of which, in the way of cut stems and grass blades, was plentiful.
Figuring from the average number of adult squirrels per square mile,
70,000, and counting on two meals per day, we find a minimum of
2,100,000 grams, or somewhat more than two tons, of green forage
devoured by the squirrels each day on a square mile of pasture.
Granted that a grazing steer eats fifty pounds of pasture forage each
day, we conclude that the squirrels on a square mile of pasture
appropriate each day the forage which might support ninety head of
cattle.
Expressing it in other ways, 750 Oregon Ground Squirrels during the
erowing season of pasture grass eat as much as one steer, and the
squirrels on every seven acres of pasture thickly inhabited by them
eat as much as one steer!
The burrows of the Oregon Ground Squirrel where the animals are
at all numerous fairly riddle the ground. Most of the openings come
to the surface at a rather steep angle and without any earth at their
mouths. Now and then there is an opening which slants to the surface
and has a good-sized mound, and such as these seem to mark the
nesting burrows as distinguished from the short, temporary, refuge
burrows, or those occupied by males. We spent the entire day of
May 16 excavating one nesting burrow, with results shown in figure 19.
The mound at the main entrance to this burrow system was rather
large in extent, though shallow. It consisted of this year’s loosely piled
earth, covering up the grass on an area of nearly two square yards and
thus marking the place conspicuously. The system of burrows, in part
at least, probably represented two seasons’ work and maybe more.
While there were only two openings to this system, there were several
points at which underground branches came nearly to the surface so
that a hard-pressed squirrel, pursued by some underground enemy,
could have quickly dug clear out and escaped overland.
As usual with ground squirrels, the runways were everywhere smooth
and free from excrement, the nest chamber in use being unexpectedly
clean. ‘The feces of the young are evidently collected by the mother and
carried to the places where her own are deposited, in the special
branches or defecatoria. Here the earth is tamped over the mass in
such a way that the pellets are kept separated by the soil particles, with
no chance to fester. The fecal pellets are dryish, anyway. Some
saved for examination, probably from the adult squirrel, prove to be
63
656 THE MONTHLY BULLETIN.
Fic. 19. Plot of a used nesting burrow of the Oregon Ground
Squirrel, as excavated by J. Grinnell and W. C. Jacobsen in a pasture
near Macdoel, in Butte Valley, Siskiyou County, May 16, 1918.
Main opening of burrow-system at a, with shallow, bean-shaped
mound nearly two square yards in extent opposite. Greatest depth
of earth in mound, 100 millimeters. Only other opening, at s, flush
with surface, and without any out-pushed earth. Mouth of burrow
at a, 100 millimeters wide by 90 high. Mouth of opening at s, 75 by
60. Dimensions of burrow at f, 75 by 60 mm.; at c, 90 by 65; at d,
60 by 60; at 0, 60 by 60. Depth of burrow at b, beneath surface of
ground, 300 mm.; at ¢, 350; at d, 200; at f, 300 ;-at 9g, 520; at h,
590; at j, 750; at k, 1,000; at 0, 660; at p, 520; at 7, 550. Branches
at i, e and ¢ came nearly to surface of ground. Old nest cavity at k, 300 mm. in
diameter, and floored with a damp mixed mass of old frazzled grasses, excrement,
and earth. At m and J, chambers, 770 and 1,110 mm., respectively, beneath surface
of ground, packed full of a mixture of excremental pellets and loose earth. Blind
terminal at n, 850 mm. deep. New nest, in use, containing many live fleas, at q;
cavity of this, 190 mm. wide by 170 high, and 700 mm. beneath surface of ground,
nearly filled with a dry clean hollow mass of shredded juniper bark and weathered
grasses. The excavating was begun at a, and the female and six third-grown
young were overtaken at s and #?, where they were about to escape.
Total length of this burrow system, 66 feet. Average diameter of burrow, 2%
inches. Volumetric content of entire system, 34 cubic feet. Greatest depth reached,
45 inches, or nearly 4 feet. j
short-cylindrical or elliptical in shape, and measure 6.5 millimeters
in diameter by from 15 to 22 in length.
There were two nest cavities in the system unearthed, an old one,
and the one in use. The latter contained a dry, hollow mass of frazzled
juniper bark and weathered stems and blades of grass. The female
parent and six third-grown young were overtaken farther along in the
burrow system, near one terminus of it, but that the nest had but
recently been vacated was shown by its feeling of warmth to the touch
and the presence of numerous lively fleas. The female proved a tartar
in defense of herself and young, biting effectively with her sharp incisor
teeth and scratching with her strong claws. This was as a final recourse,
however, as the first endeavor on the part of all the occupants, when
the burrow was opened up, was to escape and run to the nearest shelter,
such as offered by some neighboring burrow, or by a flat rock. As far
as our observations went, there was no indication that the adult male
lives in the same burrow with the female, or has, indeed, anything to
do with the rearing of the young.
The burrow system in question was found to be 66 feet long, includ-
ing the various windings and all of its branches. Its average diameter
was about 24 inches, and the volume, or cubical air content, 34 cubic
64
THE GROUND SQUIRRELS OF CALIFORNIA. 657
feet. The greatest depth reached beneath the surface of the ground was
45 inches. This was in rather dry pasture, and there was no sign of
a water-table; the soil to this depth was only moderately damp.
The notes of the Oregon Ground Squirrel are of two sorts. The
most impressive consists of a series of from 8 to 12 shrill, high-pitched
ealls, uttered in rapid succession—seep, seep, seep, seep, seep, seep, seep,
seep, seep. The tendency is to weaken on the last few syllables, but
the same pitch is nearly or quite maintained throughout. This call
seems to be uttered only by adults, and seems to signify alarm at the
first, or distant, approach of danger. One hears it taken up here and
there all over a large meadow when it is first entered. Then there is a
single shrill chirp of somewhat lower pitch, uttered now and then by
either old or young. At times one will hear scarcely a note for many
minutes, even when many of the squirrels are in sight, and then again
the calls will be given back and forth from all sides.
One old female watched from a distance of 20 feet stood stock still
for several minutes at the mouth of her burrow, in upright, “‘picket-
pin’’ fashion. The fore feet she held against her stomach in front.
When she gave the several syllabled call she opened her mouth very
wide, depressing the tongue on to the floor of her mouth so that it could
not be seen, and uttered the successive notes with much appearance of
effort. The convulsive movements of the body were synchronous with
the notes as uttered. The picket-pin attitude is really not so frequent
as a crouching one, though when it is assumed it renders the squirrel
visible a long way, especially where the grass is short. When feeding,
the squirrel hunches over on its haunches, and uses both front feet and
the fingers of these for holding and manipulating the food. When
foraging the squirrels do much slinking along, with body horizontal and
seemingly touching the ground. When a general alarm is sounded one
sees them running in every direction, with a rather clumsy and not
rapid, hopping gait. When so running the tail, short and never con-
spicuous, is held either out straight behind or raised at an angle
of 30 degrees. Often when halting, or coming to a stand on the alert,
the tail is twitched up from the horizontal several times in rapid
succession, the whole body also twitching at the same time.
Rarely does an. Oregon Ground Squirrel leave the ground, even to
climb onto a rock or log. The body is relatively heavy and the general
movements are far from nimble. In just one instance was a squirrel
observed to have actually climbed; one individual was seen at Sugar
Hill, Modoe County, up in a bush four feet above the ground (W. P.
Taylor, MS). Marshes or very wet meadows are avoided; in other
words, this species does not take to water. Still, we have the one
instance of an individual, near Canby, Modoe County, seen (W. C.
Jacobsen, MS) swimming across the Pit River. The current here was
sluggish and the channel about eighteen feet wide. The act was to all
appearances voluntary.
At the season of our special observations, the middle of May, the
Oregon Ground Squirrels were seen to be feeding on practically every
sort of pasture vegetation. Cuttings of meadow grass, blades and stems
of grain, and leaves and stems of alfalfa were seen on their mounds or
in the mouths of their burrows. As already stated, determination of
65
5—43007
658 THE MONTHLY BULLETIN.
the kinds of plants eaten, from stomach examination, proved impractica-
ble because the food is chewed so finely. Even young less than a third
erown were feeding freely on green stuff. Six young taken on May 16
were found to weigh from 65.1 to 104.7 grams, averaging 82.4 grams as
compared with 302 grams, the average weight of adults. Their stomachs
were distended with finely cut food, and were found to weigh on an
average 5.4 grams, or about one-fifteenth their total weight as against
the one-to-twenty ratio in adults. It would seem that partly grown
young eat more in proportion to their size than old squirrels—which was
rather to be expected.
There seem to be two periods of maximum daily activity above-
eround on clear days, about 9 a.m. and again in mid-afternoon. This
squirrel seems to be preéminently a sunshine forager. One day when
a thunderstorm came up in the afternoon the squirrels nearly all dis-
appeared from aboveground coincidently with the gathering of the
clouds.
The breeding season of the Oregon Ground Squirrel, as is to be
expected, varies with altitude, or, rather, with life-zone. The young are
born later in the Transition and Boreal zones, than in the Upper
Sonoran. On May 15 scores of adults were seen on Bull Meadows, near
Goose Nest Mountain, 5,000 feet altitude, in the Canadian zone, but not
one youngster was seen; while on May 16 everywhere in Butte Valley
around Maedoel, at 3,000 feet, in the Upper Sonoran zone, young were
out in great numbers. All of these were of about the same size, one-
fourth to one-third grown, showing the uniformity of time of birth
throughout a region of uniform temperature conditions. On May 19,
1910, a collecting party from the California Museum of Vertebrate
Zoology found small young, just out, on Sugar Hill, 5,000 feet altitude,
Modoe County.
There is but one litter a year, and the number to a litter is supposed
to vary from 4 to 15, averaging about 8. Exact statistics from which to
determine these figures accurately are not available. A man who was
irrigating an alfalfa field near Macdoel regularly day after day told us
that he had drowned out many families of young and that the broods he
had seen consisted of from 4 to 11, averaging, he thought, 8. Mr. W. C.
Jacobsen, from his own extensive experience with this species, considers
4 and 12 to be extremes, and 8 the average. He knows, indirectly, of
one case of 15.
The Oregon Ground Squirrels lie dormant in a dry nest beneath the ~
surface of the ground for fully half the year, even at the lowest altitudes
in the general territory inhabited by them. The bulk of the population
goes into hibernation during July and does not come out until March.
These statements are made upon the authority of Mr. W. C. Jacobsen,
who is further of the opinion that the exact time of disappearance, which
varies somewhat from year to year, is controlled by moisture and conse-
quent supply of green food. The drier the year the earlier the squirrels
20 into winter quarters, this in spite of the hotter late-summer tempera-
ture at the lower altitudes. In 1915, the squirrels in Big Valley, Lassen
County, had nearly all gone in by July 3; in Warm Springs Valley,
Modoe County, they had gone in by July 10; but on the Warner Moun-
tains, Modoe County, they were just going in on July 22 of the same
year. In 1914, a year of more moisture and better feed, the time of
66
“(LHS Lv) TAYyINOS GNNOYS ONIG1gae (1457 LV) TSYYINDODS GNNOYS AGATLNVW-N3q0109 WduHals
Ill ALW1d SAYNLINODILYOH AO NOISSINWOD ALVLS
THE GROUND SQUIRRELS OF CALIFORNIA. 659
beginning hibernation at the same points was one and one-half to two
weeks later. Individuals have been reported to us as seen aboveground
as late as the first week of September, but all reports agree that the
majority are “‘holed up’’ before the first week in August.
In the spring the animals reappear often when there is yet much
snow on the ground. In 1916 they were out in force on March 16, when
they had burrowed up in places through two feet of snow and were
nibbling the sagebrush tips (W. C. Jacobsen, MS).
Enemies of the Oregon Ground Squirrel were, under original condi-
tions, doubtless numerous and effective in keeping down its numbers.
Gopher snakes, rattlesnakes, badgers, coyotes and Swainson Hawks are
known to feed regularly on it. Mr. J. O. Miller, a professional trapper
living at Yreka, informs us that nine out of ten coyotes trapped by him
during the summer months have remains of ground squirrels in their
stomachs. One coyote taken in Butte Valley had parts of seven Oregon
Ground Squirrels in its stomach. An old-time resident near Alturas
told the senior author that the killing off of the ‘‘varmints’’ (predaceous
animals) in recent years seemed to him to have had something to do
with the increase and spread of ground squirrels. We are strongly
inclined to his belief. Hncouragement of those natural enemies which
are not in themselves seriously detrimental to man’s interests would go
far to check the undue increase of the ground squirrels.
BELDING GROUND SQUIRREL.
Citellus beldingi (Merriam).
PLATE Ill.
Other names.—Belding Spermophile; Bob-tailed Spermophile; Prairie Dog, part;
Picket-pin, part; Spermophilus elegans; Spermophilus beldingi; Colobotis beldingi.
Field characters——A medium-sized, short-tailed, “picket-pin” type of ground
squirrel, without side-stripes or other conspicuous markings, but with bright reddish
brown back. Length of body alone about 7% inches, with tail 2% inches more.
(Closely similar to Oregon Ground Squirrel, but smaller and with back reddish
krown instead of brownish gray; compare figs. 20a and 20b.)
Description.—Adult in full fall pelage: Sides of head, hind neck, shoulders, sides
of body and flanks continuously yellowish brown (numerous fine hairs which are
chiefly black, though light-tipped, lend a dusky tone to these areas) ; a tinge of olive-
ochre pervades the lower margins of those areas adjoining the light underparts; eyelids
white; whiskers black; ears dusky, finely haired, not tufted; crown of head to nose,
tawny-olive; a broad sharply outlined band of bright hazel brown running down
middle of back from between shoulders, narrowing to base of tail. Tail short, full-
haired, flattish ; above mixed hazel and black, black predominating toward end, where
also a well-defined buffy white fringe; under surface of tail conspicuously deep
cinnamon-rufous, with subterminal black interval, and buffy white fringe all around.
Upper sides of feet buffy white; claws chiefly black, with horn-colored tips; palms
naked; soles naked save for sparse hairing from heel halfway to tubercles. Under
side of head and neck, and inner sides of fore and hind legs, buffy white; belly
eream-color, with lead-color of bases of hairs showing through.
Color -variations.—As far as we can see from the series of specimens studied,
adults molt but once a year, during July. May and June specimens show clearly
the effects of wear and fading, and are grayer, with the mid-dorsal brown area much
duller than in the fresh pelage described above. Young not one-fourth grown are like
adults in color, but with mid-dorsal area paler, snuff brown, and under side of tail clay
color.
67
660 THE MONTHLY BULLETIN.
Measurements.—Average and extreme measurements, in millimeters, of twenty
mature specimens from the Yosemite section of the high Sierra Nevada are as
follows: Ten males: total length, 268 (280-280) ; tail vertebre, 66 (60-74) ; hind
foot, 44 (41-45.5); ear from crown, 9 (7-11); greatest length of skull, 44.5
(42.246.3) ; zygomatic breadth, 28.0 (26.4—29.5) ; interorbital width, 10.5 (9.7-11.0).
Ten females: total length, 260 (240-288) ; tail vertebrae, 66 (55-74) ; hind foot, 43
(40-46) ; ear from crown, 10 (8-18); greatest length of skull, 44.0 (41.3-46.5) ;
zygomatic breadth, 28.2 (26.7—28.9) ; interorbital width, 10.4 (9.7—11.0).
Relatively old individuals show greatest size, especially of skull, which also has
acquired more conspicuous ridges and sharper angles. Males average a trifle larger
than females.
Weights.—Average and extreme weights, in grams, of twenty mature specimens
from the Yosemite section of the high Sierra Nevada are as follows: Ten males, 222
(125.5-285.0) ; ten females, 240 (172-805). Average, in ounces, both sexes, about 8.
The example showing the least weight was fully adult, but was very lean. Like
other ground squirrels this species varies greatly in weight according to the amount
of fat present. Specimens taken in August and September are, as a rule, fattest.
Type locality.—Donner, Placer County, California (Merriam, 1888, pp. 317-820).
Distribution area.—Higher parts of the central Sierra Nevada (chiefly Hud-
sonian life-zone), from vicinity of Independence Lake, Nevada County, south to
southeastern border of Yosemite National Park in vicinity of Mount Lyell (see fig.
18). Altitudinal range, from 11,800 feet (as on Mt. Conness) down on western
flank of Sierras to as low as 8,100 feet (Porcupine Flat, Yosemite Park) ; on easte n
flank to as low as 6,500 feet, at western border of Mono Lake (Mus. Vert. Zool.).
Specimens examined.—A total of 48 from the following localities in California :
Nevada County: Independence Lake, 13. Placer County: “Johnson’s Pass, High
Sierras” [= Summit], 1. El Dorado County: Mf, Tallae, 1. Alpine County: Hope
Valley, 4. Mono County: Mono Lake P. O., 1; Farrington’s, Mono Lake, 8; Mono
Pass, 1; Tioga Pass, 1; Walker Lake, 1. Tuolumne County: Tuolumne Meadows, 8;
middle Lyell Canyon, 1; head Lyell Canycn, 5. Mariposa County: Mt. Hoffman,
10,700 ft., 1; Tioga Road, southeast Mt. Hoffman, 3; near Vogelsang Lake, 2; two
miles east Porcupine Flat, 1; one mile east Lake Merced, 1.
This species of ground squirrel was named after Lyman Belding, an
early resident of Stockton and a naturalist of considerable attainment.
Belding found it in the summer of 1885 in the vicinity of Summit,
Placer County, and sent a specimen to Dr. C. Hart Merriam, who later -
(1888) described the species, calling it Spermophilus beldingi.
The most notable thing about the Belding Ground Squirrel is the
great altitude of most of the area it inhabits. It is very closely restricted
to the alpine meadows of the high central Sierra Nevada. The warmer
levels below seem to be just as inimical to its welfare as the cold upper
zones certainly are to the other ground squirrels which inhabit the
middle slopes or foothills. Reference to our diagram (fig. 23) will
show some interesting facts in this regard. We would infer that the
Belding Ground Squirrel is the hardiest of all our species as regards
ability to endure long and cold winters, though here the habit of hiber-
nation must come importantly into play as tiding it over the extremes.
This squirrel occurs in fair abundance on the preferred portions of
its general range, namely, the grassy meadows in the neighborhood of
timber line. Individuals rarely occur down as low as the belt of red
firs and aspens (Canadian zone) on the west slope of the Sierras, though
on the east slope a few do occur down through the Jeffrey pine belt.
It is quite strictly an inhabitant of open levels; it is rarely or never
seen in the woods or on steep or rocky slopes. Occasionally an indi-
vidual ascends to the top of some glacier-borne boulder out in a meadow
for a look around, but we have yet to observe any greater exploit in
elimbing.
68
THE
(a) Oregon Ground Squirrel in
meadow near Klamath Falls, Oregon.
Photographed by H. C. Bryant, May 30,
-1914. Note uniform coloration with
no indication of a reddish brown patch
on back.
(c) Same squirrel as shown in Db
standing upright in characteristic
“picket-pin” attitude.
Fic,
GROUND SQUIRRELS OF CALIFORNIA.
(b) Female Belding Ground Squirrel
at entrance to burrow; Tuolumne
Meadows, Yosemite National Park.
Photographed by T. I. Storer, July 27,
1915. Note patch on back rendered
photographically nearly black, but
wun was reddish brown. Compare
with a.
(d) Sierra Golden-mantled Ground
Squirrel or “bummer,” feeding on
scraps from the camp table. Note the
distended cheek. Bullfrog Lake, 10,600
feet, Fresno County. Photographed by
J. Dixon, September 1, 1916.
20.
69
662 THE MONTHLY BULLETIN.
Probably because of the open nature of their forage ground, these
squirrels seem exceptionally timid. The shrill cries of alarm greeting
the invader of a meadow upon his approach are quickly followed by
total disappearance of the animals, at least for the time being. Each
individual seems not to wander usually more than a few yards from
the mouth of its burrow, so that but a short run intervenes at any
moment between it and safety. The tail is held down when running,
not elevated nor waved. ‘The gait is rather slow and clumsy, impressing
one observer as resembling that of a short-legged dog. ‘‘Where the
grass is short there is little up-and-down movement of the body shown
in running; but in high grass, instead of parting the stalks and pressing
them aside as it progresses, the animal advances by a series of jumps
each of which carries it up clear of the grass so that it can glimpse
about for a possible enemy’’ (T. I. Storer, MS).
When within but a few feet of the mouth of its burrow and first
taking alarm, a squirrel will rise quickly on its haunches and assume
the rigid, upright, ‘‘picket-pin’’ posture (see fig. 20c). This usually
brings the animal’s head well above the grass tops, so that it can get a
good view all about. Also it can then be seen a long way, looking in
the distance like a tent-stake or picket-pin out on the meadow. During
this pose the fore limbs are pressed closely against the body. Some-
times the animal rises still higher, supporting its whole body on its hind
feet and using its stubby tail as a prop (C. lL. Camp, MS). ‘The fact
that the nose is continually twitched up and down, as if the animal
were drawing in air, suggests that the sense of smell may be keen and
that it may be used to determine the nature of a supposed enemy. If
the observer continues his approach the squirrel suddenly deserts its
‘‘picket-pin’’ pose and dashes for its burrow, where it may hesitate a
moment on all fours for one final look before diving out of sight.
The voice of this squirrel closely resembles that of the Oregon Ground
Squirrel. The usual call of warning consists of a series of from five to
eight short shrill whistles uttered in quick succession and weakening
toward the last. Females warn their young when foraging abroad. with
a lower-pitched, double note, or bark, e-chert’. A single note, strt, is
also frequently heard.
The burrows of the Belding Ground Squirrel are generally located
in the meadows which form their forage grounds. Sometimes, near
timber line, one finds them in the scant gravelly soil between granite
boulders, but always in or near patches of the kind of bunch grass
occurring at such altitudes. The mounds are rarely conspicuous, and
the holes open up to the surface steeply. Often there is no surplus
earth at all around the mouths of the burrows, but this condition might
be accounted for by the effects of washing from heavy rain or melting
snow. Several measurements of burrows gave an average diameter of
two inches. The extent of the underground burrow system has only
been tested out in one instance (see fig. 21). In this case the burrow
was located in a wet meadow, snowbanks melting all about at the time
(June 28), and it proved to be shallow, reaching an extreme depth of
only about thirteen inches. But blind branches directed downward
indicated the probability of greater depth later in the season when the
water table had lowered and the soil dried out. The total length of
this burrow system, including all its branches, was close to 54 feet.
70
THE GROUND SQUIRRELS OF CALIFORNIA. 663
Aft al N
=
Fic. 21. Plot of a used burrow belonging to a
female Belding Ground Squirrel, as excavated by |
J. Grinnell and T. I. Storer in a meadow near the
Tioga Road, on Snow Flat, 8,700 feet altitude,
Yosemite National Park, June 28, 1915.
Main opening of burrow at a (down this the
squirrel went when shot, and was subsequently
found at c); two other openings at a’ and a”; at b
and b’ blind branches directed downward (the squir-
rel may have essayed to dig deeper at these points
but was discouraged by water); food materials,
including lily tubers, in chamber at f; in the enlarge-
ment at the point marked nest was an accumulation
of dry grass, the remains of an old nest or the
beginning of a new one (the young would not have
been born for about two weeks); boulder at g |
bulged out over the portion of the burrow adjacent
to it, affording protection to the supposed nest-
chamber.
Diameter of burrow, 45 to 65 millimeters; average
of several measurements, 52. Average depth beneath
surface of ground, about 135 mm. Greatest depth,
at 6 and 0b’, 330 and 270, respectively. Total length
of system, about 54 feet.
The burrow system above described belonged to just one squirrel, an
adult female, which was found to contain five embryos, the only exact
evidence we have as to the number of young to a litter. This was at
8,700 feet altitude, on Snow Flat, Yosemite Park, on June 28. Half-
erown young were common on Tuolumne Meadows, 8,600 feet, July 16.
Young two-thirds grown have been taken at Independence Lake, Nevada
County, 7,000 feet altitude, as early as July 13. Three third-grown
young were seen, and one of them photographed (fig. 22), at 6,800 feet
altitude near Williams Butte, Mono County, June 28. There is thus
probably some variation in time of appearance of the young, with alti-
tude, the animals at the highest levels being born latest in the season.
The young are out quite generally by the 15th of July. Only one litter
71
664 THE MONTHLY BULLETIN.
is born each year. On July 31, on Tuolumne Meadows, Yosemite Park,
young Picket-pins were out in parties of six mostly, and sat about the
mouths of their burrows or foraged in the very near vicinity. When
frightened all members of each group darted for their refuge at the
same time, crowding into the hole with some difficulty.
Belding Ground Squirrels become very fat in late summer and hiber-
nate regularly; but exact dates of beginning hibernation in the autumn
and emerging in the spring are wanting. We do know that they are
not averse to running about over the surface of the snow at high alti-
tudes in June, and so probably come out much earlier, and that in one
year, 1915, they were still out as late as October 7 in the vicinity of
Ten Lakes, Yosemite Park, although a light snowfall had already
occurred. They were numerous on the extensive meadows in Tioga
Fic. 22. Third-grown young Belding Ground Squirrel; photographed by J. Dixon,
June 28, 1916, near Williams Butte, Mono County.
Pass on September 28. It is evident that, in spite of its more elevated
habitat, the Belding Ground Squirrel goes into its winter sleep a full
two months later than the Oregon Ground Squirrel.
Like the Oregon Ground Squirrel, the Belding feeds largely on grass
stems and blades. An individual has been seen gathering seeds from
grass heads, pulling the latter down to its mouth with its fore feet;
but it is certainly not the seed-eater that the California and Golden-
mantled ground squirrels are. Neither is there evidence that the Belding
stores up much food. As with the Oregon species, its cheek-pouches
are small (see fig. 13b). At Soda Springs, on Tuolumne Meadows, the
Belding Squirrels have been seen foraging like rats about the mule
corral.
72
THE GROUND SQUIRRELS OF CALIFORNIA. 665
The enemies of this species of squirrel probably include most of the
carnivores of the high mountains. A Mountain Weasel (Mustela ari-
zonensis) has been seen to kill one by biting it through the back of the
neck (C. L. Camp, MS).
The Belding Ground Squirrel bears no decided economie importance,
save as might be involved in the grass it eats. Its habitat falls only
within the summer range of sheep and cattle, and its numbers are
nowhere so great as to be likely to reduce the crop of pasture grass
to any material extent.
STEPHENS SOFT-HAIRED GROUND SQUIRREL.
Citellus mollis stephensi (Merriam).
Other names.—Stephens Spermophile; Picket-pin, part; Stephens Ground Squir-
rel; Spermophilus mollis stephensi. 5
Field characters.—Small size combined with very short and slender tail and gray
coloration (no stripes or special markings) ; ear small; length of body alone about 6%
inches, with tail about 2 inches more.
Description.—Nearly full-grown young in summer pelage (June): General tone
of coloration on upper surface of body, buffy gray; top of head from nose to hind
neck, pale cinnamon-buff, deepest on nose, and changing into color of back on
shoulder; cheek to shoulder, olive-buff; eyelids white; whiskers black; back light
drab with a faint effect of fine dappling; the hairs on the back lead-colored at extreme
bases, then gray, then bister, and tipped with buffy white. Upper surfaces of feet
dull white; palms naked; soles of hind feet clothed with dull whitish hairs to about
halfway forward from heel; claws blackish, with horn-colored tips. Tail flat-haired,
but narrowly so, and tapering from base to tip; upper surface buffy drab; beneath
dull white at base, becoming dusky pinkish buff toward end. Lower surface of body
silvery white, faintly buff tinged, particularly as forming a band along each side, and
with much of the leaden-hued bases of the hairs showing through.
We have at hand but two specimens of this ground squirrel, and these are both
immature.
Color variations.—A considerable series of specimens of Citellus mollis (sub-
species?) at hand from northern Nevada make it seem likely that stephensi varies
in color but little from the coloration as here described; probably old adults are
grayer, with little or none of the cinnamon-buff about the head. The summer pelage
at all ages is notably soft and silky as compared with that of most other species of
ground squirrels at the same season. There is possibly a distinct winter pelage, with
regular molts in spring and fall; but we have no specimens to indicate this.
One of our two specimens has the tail much flatter, and broader ended, than
the other; but this we think is due to the way the tail was wired when the skin
was prepared. The usual thing is for the tail to taper from base to tip, thus quite
unlike the condition found in the Mohave Ground Squirrel.
Measurements.—Nine specimens from the head of Owens Valley, in California,
average, in millimeters as follows: total length, 212; tail vertebre, 50; hind foot,
32.4 (Merriam, 1898, p. 70).
The two immature specimens in the Museum of Vertebrate Zoology, from near
Mono Lake, measure as follows, the first figures given being for the male, the second
for the female: total length, 195, 185; tail vertebrae, 45, 45; hind foot, 32, 32; ear
from crown, 4, 4; greatest length of skull, . . ., 35.6; zygomatic breadth, 21.8, 22.0;
interorbital width, 7.4,....
Weights.—Our two specimens weigh, in grams, as follows: male, 83.6; female, 78.0
(in ounces, about 8 and 2%, respectively).
Type locality.—Queen Station, near head of Owens Valley, Nevada [in Esmeralda
County, just across California boundary] (Merriam, 1898, p. 69).
73
666 THE MONTHLY BULLETIN.
Distribution.—Within the state of California, in only a very limited area com-
prising the sagebrush valleys of eastern Mono County, namely from southeastern
edge of Mono Lake to head of Owens Valley in vicinity of Benton Station (see fig. 18).
Life-zone, Upper Sonoran chiefly, barely entering Transition locally (see fig. 28).
Southernmost known locality of occurrence, Taylor Ranch, in Owens Valley, two miles
south of Benton Station. Altitudinal range, 5,300 to 7,300 feet.
Specimens examined.—A total of 2, both from Mono County: Mono Mills, 1; Dry
Creek, 1.
The Soft-haired Ground Squirrels belong to the Great Basin region
of the western United States and get into our California list only on
the basis of the occurrence of one of the subspecies, the Stephens, in a
few places along the eastern border of the state. This is a distinctly
different type of ground squirrel from any of our others, notably in the
soft, silky ‘‘feel’’ of the hair. In addition, the small size, short slender
tail, and uniform light grayish coloration make a combination of-
characters which is unique among our species.
Unfortunately, our own personal experience with this species has
been very limited. In September of 1917 the two of us made especial
search for it at the extreme head of Owens Valley. But we were too
late in the season; locally well known in the vicinity of Benton, we
were assured by the ranchers that the animals had all “‘holed up’’ by
about the end of July. On the Pellisier Ranch, five miles north of
Benton Station, ‘‘Picket-pins’’ were declared to have been present ‘‘by
the million’’ from April until July, but it was averred that by the last
of August they had all disappeared. Numerous round holes in the
ground among the sage bushes were pointed out to us as belonging to
these squirrels. There was abundant evidence that coyotes and badgers
regularly dig them out. Also we were told that at the season the
squirrels are above ground the Indians capture many for food.
On the Taylor ranch this squirrel was reported to be plentiful, but
to vary much in numbers from year to year. In the spring of 1916 it
was abundant; in 1917 scarcely any were seen.
In the sand-dune area along the east side of Mono Lake, the junior
author saw several Soft-haired Ground Squirrels on June 10, 1916.
The sand was fairly covered with their tracks. Those individuals seen
on June 11 near Dry Creek in the same neighborhood were notably
tame. They gave the impression of being flat-bodied, and slid along
the ground like lizards, stopping to scrutinize the intruder from the
shelter of the first bush reached. One was captured under a bush by
being pinned down with the gun.
Mr. Frank Stephens of San Diego, for whom this subspecies was
named, states (1906, p. 71) that he found the animals ‘‘rather common
in the valleys of eastern Mono County.’’ They were feeding on the
sagebrush and were exceedingly fat. The date of capture of the type
was July 12, 1891 (Merriam, 1898, p. 69).
74
feta) 4
“((4HOIY Lv) TAYYINOS GNNOYS AZAVHOW ‘(L457 LV) THYYINOS GNNOYS Gatlvl-GNNOY WWNA
Sy pepe, 12D Vos
ep ay
ane oA
Al ALW1d SYNLINDILYOH AO NOISSINWOD ALVLS
THE GROUND SQUIRRELS OF CALIFORNIA. 667
MOHAVE GROUND SQUIRREL.
Citellus mohavensis (Merriam).
PLATE IV.
Other names.—Mohave Desert Spermophile ; Mohave Desert Ground Squirrel, part ;
Spermophilus mohavensis; Citellus tereticaudus mohavensis, part.
Field characters.—A small-sized, brown-colored ground squirrel, without stripes
or special markings whatsoever on the body, but with short broadly haired tail,
white underneath; ear a mere rim; length of body alone, about 64 inches, with tail
about 24 inches more.
Description.—Adult in full winter pelage: General tone of whole upper surface
from nose to base of tail cinnamon drab; hairs on back when examined closely are
seen to be lead-color at base, then ashy white, then army brown, and tipped with
white; mixed with these hairs are a few of solid black color, and on the rump some
which are black with a white interval near end. lTyelids white, but cheeks like
back; rim of ear and upper sides of feet tinged with light pinkish cinnamon; palms
of fore feet naked; soles of hind feet clothed with long buffy hairs; claws black with
horn-colored tips. Under surface of body silvery white, but slaty bases of hairs show
through making the general effect light gray. Under surface of the flattish stubby
tail pure white; upper side like back at base, becoming mixed black and white toward
end; extreme end with white fringe. Adult in summer pelage: Coat very much
coarser and shorter than in winter; general color tone browner, close to cinnamon,
but a grizzling effect is produced by white hair-tippings everywhere on upper surface.
Sides of face paler than in winter, and lower surface of body pure white, owing to
lack of lead-color at bases of individual hairs.
Color variations.—Specimens of dates May 3 and 12 are in process of molt from
winter to summer pelage. Patches of worn and yellowed winter hairs remain on the
fore back and rump. ‘The tail is seemingly not included in the spring molt, and the
old tail hairs become crinkled and broken at the ends; the white of the under side
is dingy, and a dark subterminal band around the end of the tail shows through.
Measurements.—Average and extreme measurements, in millimeters, of seven adult
specimens (5 males, 2 females), from the northern part of the Mohave Desert are
as follows: Total length, 224 (212-230) ; tail vertebre, 62 (42-72); hind foot, 36
(34-87) ; greatest length of skull, 38.6 (88.1-39.0); zygomatic breadth, 24.3
(23.6—-25.8) ; interorbital width, 8.7 (8.2-9.2).
The two sexes appear to be alike in measurements as well as in coloration.
Weights.—An adult male, not particularly fat, was found to weigh 104 grams
(about 32 ounces).
Type locality—Mohave River, California (Merriam, 1889, p. 15). More exactly,
near Rabbit Springs, about 15 miles east of Mohave River at Hesperia, in San
Bernardino County (Stephens, in conversation, January 1, 1916).
Distribution area.—Not continuous; western parts of the Mohave Desert, from
Haiwee, Inyo County, south to Rabbit Springs, San Bernardino County (see
fig. 18). Life-zone, Lower Sonoran, though only in its upper portion apparently.
Altitudinal range, 2,500 to near'y 4,000 feet.
Specimens examined.—A total of 8, from the following localities in California :
Inyo County : Haiwee Meadows, 3,750 feet alt., about ten miles south of Owens Lake,
2 (in coll. U. S. Biol. Surv.) ; Little Lake, 3,100 feet, 2 (Mus. Vert. Zool.). San
Bernardino County: Salt Wells Valley (eastern edge near Inyo County line), 2,500
feet, 83 (U. S. Biol. Surv.) ; Rabbit Springs, 2,900 feet, east of Mohave River, 1 (in
coll. F. Stephens).
The Mohave Ground Squirrel, although first discovered in 1886 by
Mr. Frank Stephens of San Diego, has remained about the least known
of all our rodents. Only four rather scattered localities of occurrence
are definitely known, as listed above under ‘‘Specimens examined.”’
The dates represented are March 22 and 24, May 3 and 12 and June 5.
75
668 THE MONTHLY BULLETIN.
The two specimens in the Museum of Vertebrate Zoology were trapped
on the first two specified dates, in 1918, on the hillsides immediately
west of Little Lake. They were daytime-taken in oat-baited rat-traps
set beneath creasote bushes on gravelly ground. In spite of diligent
search by the collectors everywhere in the neighborhood, not one of this
species was seen alive. No information is available to us in regard to
either behavior or food.
This ground squirrel is altogether distinct from Citellus tereticaudus.
There is no indication of intergradation with that species, as stated by
Elliot (1904, p. 291). In fact, the animals reported by that author
from Daggett were all probably in reality tereticaudus, which species is
known to us to be present at Daggett. The tail of mohavensis is always
much shorter and more broadly haired than in tereticaudus, the claws
are stouter, the cheeks are brownish instead of white, the under side of
the tail is white, instead of buffy with brown mottlings toward the end,
the quantity of winter pelage is greater, and the general tone of colora-
tion is always decidedly dark.
The fact that the under side of the tail is white, as in the Antelope
Ground Squirrel, leads us to suspect some such special habit of display-
ing this member as is possessed by the latter animal. But this is mere
speculation. The relationships of mohavensis as indicated by structural
features are thought to lic rather with Citellus than with Ammosper-
mophilus. :
YUMA ROUND-TAILED GROUND SQUIRREL.
Citellus tereticaudus tereticaudus (Baird).
PLATE IV.
Other names.—Round-tailed Spermophile; Yuma Ground Squirrel; Mohave
Desert Ground Squirrel, part; Spermophilus tercticaudus; Xerospermophilus tcreti-
caudus ; Citellus tereticaudus mohavensis, part.
Field characters.—A small ground squirrel, of slender build, and of pale brown
color (no stripes or other markings) ; tail long and slender, not broadly haired; ears
very small, mere rims; length of body without tail about 6 inches, with tail about
32 inches more.
Description.—Adult in winter pelage: Whole upper surface from nose to and
including tail, light pinkish cinnamon in general tone; individual hairs lead-colored
at extreme bases, then dull white, then pinkish cinnamon, and with tipping of white.
Eyelids and whole lower surface to root of tail, white; side of head and neck
including ear dull white; whiskers black; hairs of belly lead-colored at extreme bases.
Upper surfaces of feet dull buffy white; claws dark brown basally, becoming horn-
eolor at tips; soles of feet haired save for under sides of toes. ‘Tail cylindrical in
shape, a little more heavily haired toward end than at base; under side dull buff, with
black mottlings in fine pattern toward end; above like back on basal half, becoming
black and buff mottled toward end; hairs at tip of tail brown at their bases, then buff,
then broadly black, and with white ends.
Adult in summer pelage: Coat short and harsh as compared with winter coat;
color above brighter pinkish cinnamon. Otherwise as in winter, but the tail, which
apparently does not molt, pale brown and still slenderer, due to the fading out of the
dark colors and to the wear and consequent shortening of the hairs.
Color variations.—Young partly grown are colored like summer adults, but the
pelage is not quite so harsh and on the under surface is so sparse as to allow
the bare skin to show through in places. There are two molts in the adults each year
76
THE GROUND SQUIRRELS OF CALIFORNIA. 669
and two distinct pelages separated by these. The spring molt occurs during April
(March 28 to May 1 according to specimens at hand), and the fall molt probably
during October though there are no specimens available to show its extent. The
remnants of the winter pelage during the spring molt become faded in some specimens
to a dull yellowish tone. This molt advances in a general way from the front back-
ward, but specimens often show a patchy or mixed coat on the back and rump.
Measurements.—Average and extreme measurements, in millimeters, of seventeen
adult specimens from the Colorado and Imperial valleys are as follows: seven males:
total length, 247 (225-261); tail vertebre, 95 (85-107); hind foot, 86 (34-87) ;
greatest length of skull, 37.1 (85.2-88.2); zygomatic breadth, 23.5 (22.5-24.4) ;
interorbital width, 8.9 (8.8-9.5). Ten females: total length, 241 (216-258) ; tail
vertebre, 91 (75-102); hind foot, 36 (83-88); greatest length of skull, 36.0
(34.3-88.2) ; zygomatic breadth, 22.2 (21.3-23.4) ; interorbital width, 8.6 (8.0-9.5).
Males are seen to be slightly larger than females. The ears in this species are
small, the rims rising not more than 8 millimeters (# inch) above their inner base.
In but few specimens did the collector attempt to secure the measurement of the ear.
Weights.—Stephens (MS) found two females and a male to weigh together 12
ounces, an average of 4 ounces each. “All were thin.”
Type locality—DFort Yuma [Imperial County], California (Baird, 1857, pp.
815-3816). :
Distribution area.—Low-lying sandy areas on the Colorado and Mohave deserts.
Life-zone, Lower Sonoran (see fig. 23). More specifically: the Imperial Valley west
as far as La Puerta (Mus. Vert. Zool.) in extreme eastern San Diego County, north
to the southern end of Salton Sea, and east to old Fort Yuma; thence north along
the Colorado River nearly or quite to the Nevada line; and from the vicinity of
Needles and Blythe, in the Colorado Valley, northwestward across the central part of
the Mohave Desert to at least as far as Kramer (Grinnell, MS), in west-central
. San Bernardino County. Altitudes of occurrence, from 200 feet below sea-level to
2,300 feet above. The range of this species is not continuous over the area just
indicated (see fig. 18), but consists of many colonies more or less distantly isolated
from one another.
Specimens examined.—A total of 28 from the following localities in California :
San Bernardino County, one-half mile north of Barstow, 1; Daggett, 1; Blythe
Junction, 4; Needles, 3. Imperial County: south end of Salton Lake, 6; six miles
south of Holtville, 2; Coyote Well, 4; Pilot Knob, 4; Colorado River opposite Cibola,
2. San Diego County: La Puerta, 1.
The Yuma Round-tailed Ground Squirrel was first made known to
science in 1857 from specimens taken by an army officer stationed at
old Fort Yuma, which was situated on the California side of the Colo-
-rado River opposite the present town of Yuma. It inhabits the hottest
of our southeastern desert valleys. Its metropolis lies in the Imperial
Valley and thence north along the valley of the Colorado; a few colonies
occur also on suitable parts of the Mohave Desert. Over this general
region the species is by no means continuously distributed. It seems to
be very particular in its requirements, only level ground of a sandy
nature being as a rule inhabited at all. Places are preferred where
wind-drifted sand has been accumulated into mounds about the bases
of mesquite, creasote bushes, or salt bushes. Here the burrows are to
be seen opening up among the stems of the partly buried shrubs; and
the animals, if not actually seen themselves, are shown by their tracks
in the sand surface to be in the habit of foraging out across the bare
intervals for the seeds which are to be found sifted among the sand
particles. i
The squirrels themselves are usually shy and by reason of their
obscure coloration and especially the shimmering glare on the desert
surface are not readily observed unless particularly sought for. Neither
are their total numbers very great even where conditions are fairly
77
670 THE MONTHLY BULLETIN.
favorable. While our observations show them to be strictly diurnal in
habits, we have noted an apparent aversion to direct sunshine. Perhaps
this is because the sunshine on the desert is in summer so intense as to
be quickly fatal to any small animal exposed to it for long. We know
for a fact of squirrels caught in traps by oue foot or merely a toe, on
open ground, which have quickly succumbed—‘sun-cooked’’ is the
ower |\Upper fe Bele ;
—{
Gifellus .beecheyi beecheyi :
Cifellus beechey fisheri
Citellus beecheyi nesioficus
Citelus douglas//
Citellus variegatus grammurus
Cifellus ore gonus
Cifellus beldingt
Cifellus mollis stephensi
Citellus mohavens/s
Citellus fereticaudus fereticaudus
CiteHus terelicaudus eremonomus Pa
Citellus tereticaudus chlorus
Callospermophilus chrysodeirus chrysodeirus ala
Callospermophilus chrysodeirus perpallidus
Callospermophilus chrysodeirus bernardinus
Qmmospermophilus feucurus /eucurus —e
=.
Fic. 23. Diagram showing the ranges of the ground squirrels of California accord-
ing to life-zones. (For life-zone map of California, see Grinnell, 1913, pl. 15.)
Ammospermophilus nelsoni nelsoni
Qmmospermophilus nelsoni amplus
term we use for such victims. At any rate, the squirrels are seen
crossing open spaces but momentarily, and thenceforth they remain 1
the shade of bushes until they take final alarm and descend into their
burrows.
The long, slender, ratlike tail is exclusively characteristic of this
species of ground squirrel. The body, too, is rather slender, though
after a full meal of green stuff individuals have been seen which showed
a rather pot-bellied outline. The mere rims of ears give the animal a
round-headed look. The movements are rather more agile than in most
of its relatives. It not infrequently climbs up into bushes to a height
of four or five feet, but here it becomes clumsy.
The voice of the Round-tailed Ground Squirrel is unmistakable when
once learned. As far as known to us, but one kind of note is uttered, a
single high-pitched squeak or shrill whistle, seep, uttered only at rather
long intervals, never in a series as with some others of the ground
squirrels. The quality of this call is such that the direction from which
78
THE GROUND SQUIRRELS OF CALIFORNIA. 67]
it emanates is difficult to fix; also the distance is hard to determine. It
seems to be given as a warning by an individual, either located within
the mouth of its burrow (Stephens, 1906, p. 70) or when standing
motionless under a bush. C. L. Camp (MS) records that he has seen
an individual, when its curiosity was aroused, stand high up on its hind
legs and utter its ‘‘sharp squeak’’ with the mouth wide open, at the
same time ‘‘giving the thorax a violent contraction.’’
Facts in regard to the breeding of this squirrel are shown in the
following data. On March 15 (1914) near Barstow a male Round-
tailed Ground Squirrel was seen abroad which proved astonishingly
indifferent. ‘‘It came up to where we were digging out a kangaroo rat
colony, smelling into various burrows, evidently intently hunting for a
female. The testes of this animal were enormous, dragging on the
ground behind it as it waddled along’’ (Grinnell, MS). Two females
captured in the valley of the Colorado River opposite Cibola, April 3
and 4 (1910), were found to contain six and four embryos, respectively ;
young about half grown were taken at Needles July 15 and 19 (1909)
(Grinnell, 1914, p. 224). Stephens (1906, p. 70) says that the breeding
season falls in March and April and that the number of young in a litter
is four to seven. In spite of the long hot period each year in the habitat
of this species, there is no evidence to show that more than one litter
is reared annually.
There is a period of inactivity during midwinter, when these animals
are not seen abroad. Whether or not there is regular hibernation, as
with the species of colder regions, we do not definitely know; but this.
seems to be the case.
‘‘The food is seeds the greater part of the year; these are stored to
some extent. In the spring, during the few weeks when green vegetation
is obtainable, leaves and buds are eaten voraciously’’ (Stephens, 1906,
p. 70). In our experience, stems of the squaw-tea (Hphedra) and
leaves of the mesquite form an important element of the diet wherever
and whenever obtainable.
In June, 1918, W. C. Jacobsen (MS) found several colonies of Yuma
Round-tailed Ground Squirrels in the Imperial Valley within five or
six miles south of Holtville. The interesting thing was that here the
animals were invading the cultivated fields and were finding alfalfa
suited to their tastes. Individuals were seen to eat the leaves of the
alfalfa with avidity, but left the stems uneaten. Many dry stems were
found lying about near the mouths of their burrows. At another
point, near Bond Corners, oat hulls were seen around burrows.
There is a possibility, therefore, that this strictly desert rodent might
come to have an economic bearing on the reclaimed sections of the
desert. Whether or not it will become a serious pest remains to be seen.
One note of interest in this connection is furnished by Stephens (MS),
who says that at Silsbee, while occasionally getting into the fields, the
Round-tails were easily drowned out. As far as known to us, this
species never drinks water even when within reach of it. In most parts
of its range and at most seasons of the year water is secured only
through chemical elaboration from its dry or nearly dry food materials.
It is currently reported by the farmers in Imperial Valley that the
native desert animal life quickly disappears when the land is brought
under cultivation and especially irrigation.
79
672 THE MONTHLY BULLETIN.
DEATH VALLEY ROUND-TAILED GROUND SQUIRREL.
Citellus tereticaudus eremonomus Elliot.
Other names.—Death Valley Spermophile; Citellus eremonomus.
Field characters——Exactly as for the Yuma Round-tailed Ground Squirrel.
Description.—As for the Yuma and Palm Springs Round-tailed Ground Squirrels,
but coloration decidedly darker than in either, near wood brown. ‘This feature is
characteristic in all of the eight skins of eremonomus at hand.
Color variations.—The time of the spring molt is indicated by a specimen of date
April 10, in which new summer pelage shows on the head and rump; an example of
May 3 is in absolutely new summer pelage except, of course, for the tail. One speci-
men has a bobbed tail, with an abnormal tuft of hairs at the end, showing con-
spicuously a band of black and then a terminal band of white. Most of the skins
show a curious spotting of the rump which is clearly not due to color markings on
the hairs, but to places where hairs are absent, so that the dark-colored skin and dark
bases of adjacent hairs show through. These may indicate scars from insect bites.
Measurements.—Average and extreme measurements, in millimeters, of eight adult
female specimens from Death Valley are as follows: total length, 249 (240-255) ;
tail vertebrse, 91 (87-93); hind foot, 35 (34-36); ear from crown, 2.1 (2.0-3.0) ;
greatest length of skull, 36.0 (34.8-86.6) ; zygomatic breadth, 22.5 (22.0-23.4) ;
interorbital width, 8.7 (8.8-8.8). No males are available.
Weights.—Average and extreme weights, in grams, of eight adult females from
Death Valley are as follows: 144.3 (121-158). The average, in ounces, is 5.1.
Type locality—Furnace Creek [Ranch], Death Valley, Inyo County, California
(Hiliot, 1908, p. 243).
Distribution area.—Floor of Death Valley, in Inyo County. Life-zone, Lower
Sonoran. Only known locality of occurrence, vicinity of Furnace Creek Ranch
(Greenland Ranch), —240 to —175 feet altitude. Apparently cut off from its nearest
relative, tereticaudus proper, by the elevated rim of the Death Valley basin.
Specimens examined.—A total of 8, all from the near vicinity of Furnace Creek
Ranch, —178 feet, Death Valley, Inyo County.
As far as known, this race of Round-tailed Ground Squirrel is limited
in its distribution to the bottom of the deep sink known as Death Valley,
and even there to the belt of mesquites immediately around the margin
of the alkali flats at the lowest level. The entire habitat of this Death
Valley subspecies thus lies below sea level, a. distinction probably not
shared by any other rodent in America.
Our experience with this squirrel was obtained during April and
early May, 1917, in the immediate vicinity of old Furnace Creek Ranch,
now known as Greenland Ranch. The animals at the time of our visit
were not invading the cultivated land, though we were assured by the
foreman that they had come into the alfalfa fields in previous seasons.
Since this was the type locality of the subspecies, special efforts were
made to obtain a series of specimens. The animals were not abundant,
and proved practically impossible to trap. Shooting was resorted to,
though with but lttle better results. The following notes were made
on April 10 by the senior author while hunting them.
During a two hours hunt at midday at least five individuals were
heard on the mesquite-crowned sand dunes within a mile southwest of the
ranch. The warmth had seemingly brought them out, for the previous
two or three days had been relatively cool, and none had been seen.
A temperature of over 100° in the shade seemed to be necessary to
80
THE GROUND SQUIRRELS OF CALIFORNIA. 673
bring the animals out into full activity. ‘‘I caught sight of one standing
upright at the mouth of its burrow, squeaking, and of two others run-
ning over the sand beneath the trailing green mesquite branches. The
lines of footprints in the sand centering at the mouths of their burrows
are diagnostic. The animals are extremely shy, going below ground
-at the slightest alarm. By standing ten minutes or so ‘at attention’
about fifteen yards from the mouth of a burrow down which one van-
ished, I finally saw the top of its head reappear to the level of its eyes.
This position was maintained for many minutes, until the animal
suddenly raised its whole head and neck into view, when I shot it.
“‘Later, while I was lying prone on the sand under a mesquite, one
came up to within eight feet of me and gave its shrill, wiry ery, or
squeak. A mere movement on my part, and it vanished, quick as
thought.’’ It was found that a little ‘“‘screeping’’ (lips to back of
hand) would often bring one of the squirrels stealthily investigating
through the brush, provided the observer kept perfectly motionless
himself and was possessed of patience. The squirrel would sometimes
squeak, apparently in answer, and thus be called into very close ‘‘aux’’
range. The burrows were as a rule located in the periphery of a large
mesquite clump, where they were shaded by the radiating leafy branches
which trailed down the sandy slopes. Not more than three burrows
certainly of this rodent were to be found about any one clump.
The mesquites during early April were just coming out into full new
foliage. The stomachs of the squirrels shot were distended with masses
of finely chewed mesquite leaves and nothing else. This, in fact, was
absolutely the only kind of vegetation anywhere in sight for hundreds
of yards. In one instance the total weight of the freshly killed animal
was found to be 154.5 grams; of the full stomach alone, 28.7 grams, or
19 per cent (near one-fifth) of the total weight. In other words, a
Death Valley Round-tailed Ground Squirrel may eat close to one- four th
its own weight of green mesquite leaves.
No young were seen by us up to the time of our departure, but they
are probably born about the first of May. Two old females captured
April 10 and 12 contained four and three embryos, respectively.
PALM SPRINGS ROUND-TAILED GROUND SQUIRREL.
Citellus tereticaudus chlorus Elliot.
Other names.—Pale Spermophile; Crtellus chlorus.
Field characters——Hxactly as for the Yuma Round-tailed Ground Squirrel.
Description —As for the Yuma Round-tailed Ground Squirrel, but tone of colora-
tion more grayish, avellaneous rather than light pinkish cinnamon. This difference
holds through all pelages and gives the impression of an olive-colored animal, when
close comparisons are made with series of the other related ground squirrels.
Color variations.—Specimens showing the spring molt to be in process bear dates
from March 29 to as late as June 3. As with the other races of tereticaudus the
pelage on the tail is not replaced during the spring molt and it becomes greatly faded
and worn. In extreme cases the tail with its shortened, singed-looking hairs is a
dirty pale brown color throughout, and as slender as a wood- rat’s tail. The summer
. 6—43007 81
674 THE MONTHLY BULLETIN.
coat is so short and thin that any scars there may be in the skin show through as
dark spots. These appear irregularly on certain specimens, usually those which
examination of the teeth shows to be the older individuals.
Measurements.—Average and extreme measurements, in millimeters, of twenty
adult specimens from Whitewater, Palm Springs and Mecea, in Riverside County, are
as follows: Ten males: total length, 241 (220-251); tail vertebrae, 90 (79-97) ;
hind foot, 86 (385-40) ; greatest length of skull, 36.6 (35.2-38.9) ; zygomatic breadth,
23.0 (21.6—-24.6) ; interorbital width, 8.9 (8.0-9.7). Ten females: total length, 240
(229-264) ; tail vertebra, 89 (80-102) ; hind foot, 35.7 (34-89) ; greatest length of
skull, 86.1 (35.6-37.5) ; zygomatic breadth, 22.8 (22.0-23.4) ; interorbital width, 8.8
(8.6-9.4) .
Type locality—Palm Springs, Riverside County, California (Hlliot, 1908, p. 242).
Distribution area.—The northwestern arm of the Colorado Desert between Salton
Sea and San Gorgonio Pass (see fig. 18). Life-zone, Lower Sonoran. More specifi-
cally, the Coachella Valley, entirely within Riverside County, from Mecca northwest
to Whitewater Station; altitude from —200 to 1,180 feet.
Specimens examined.—A total of 41 from the following localities, all in Riverside
County : Palm Springs, 6; Whitewater Station, 18; Mecca, 17.
This race of Round-tailed Ground Squirrel was first made known from
specimens collected in the vicinity of Palm Springs, out on the Colorado
Desert near the northeast base of San Jacinto Peak. Subsequent
exploration has shown it to be limited to the relatively small area of flat
desert lying between Salton Sea and the upper part of San Gorgonio
Pass, and shut in narrowly by the mountain walls on either side.
The slight features by which this subspecies is distinguishable from
the Yuma Round-tailed Ground Squirrel of the Imperial Valley south-
east of Salton Sea may be inferred to have arisen as a result of the
action of the body of water which formerly filled the Salton Sink to
sea level in cutting off or isolating the animals in the northwestern arm
of the Colorado Desert and thus giving them a chance to develop
peculiarities all their own. The ancient predecessor of the present
Salton Sea is known to geologists as Blake Sea, and this inland sea
extended from the base of the Chocolate Range of mountains on the
northeast to the very foot of the Santa Rosa Mountains on the south-
west, thus constituting an impassable barrier to any animal closely
restricted, as is the Round-tailed Ground Squirrel, to dry, level, sandy
eround. However this may have been, the Palm Springs subspecies
now ranges down the Coachella Valley from the northwest nearly to the
upper end of the present Salton Sea, in the vicinity of Mecea. One
can imagine the animal life of the desert floor now retreating, now
advancing, with the fluctuations of the old Blake Sea since the time it
was first cut off from the Gulf of California by the slowly growing delta
of the Colorado.
The general habits of the Palm Springs Round-tailed Ground Squirrel
are probably closely similar to those of the Yuma and Death Valley
animals. The first-named is fairly common locally, though it rarely
forces itself on the attention; it has to be specially looked for. At
Mecca in March and April (1908) one or two were caught nearly every
day in oat-baited rat-traps set on sandy mounds beneath mesquites.
Yet the animals themselves were rarely seen. On April 26 one was
surprised up in a mesquite; upon being shot it was found to have parts
of a mesquite flower in its mouth. The senior author was told that at
the experimental date farm near Meeca these squirrels had been seen
eating the dates.
82
THE GROUND SQUIRRELS OF CALIFORNIA. 675
At the railroad station of Whitewater this animal was found by
museum collectors to be common, June 3 to 5 (1908), in a tract of sand
dunes nearby. The shrill calls or whistles were heard frequently, and
many of the squirrels were trapped. Some of these were young, one-
third to one-half grown. The old males and part of the old females
taken then were very fat; all the rest lean. A female taken at Mecca,
March 27, was found to contain five large embryos. The extent of the
breeding season is thus indicated. Doubtless but one litter is raised
each year.
Search in the vicinity of Palm Springs in December and January of
different years has failed to show the presence of these squirrels actively
abroad; so that it is likely that they hibernate during midwinter. In
1916, Swarth (MS) found them out on February 4 in a tract of sandy
soil about a mile east of the village. They occurred in small scattered
colonies, each ‘‘colony’’ marked by twelve to fifteen open holes on level
eround among creasote bushes. ‘‘Parts of the burrows were shallow,
so that a person would sink through into them ankle deep.’’ The
animals when alarmed would scurry to their holes and disappear into
ae but would presently poke up their heads and utter ‘‘faint little
arks.’
No information has come to us that would indicate any decided
economic bearing on the part of the Palm Springs Round-tailed Ground
Squirrel. Because of its dry-land preferences it is likely that reclama-
tion and irrigation of the land would drive it away rather than attract
it. Thus the reaction would be just the opposite to that in the case of
the Oregon Ground Squirrel and similar species.
SIERRA GOLDEN-MANTLED GROUND SQUIRREL.
Callospermophilus chrysodeirus chrysodeirus (Merriam).
PLATE Ill.
Other names.—Gilded Squirrel; Gilded Ground Squirrel; Copper-headed Ground
Squirrel; Copperhead; Yellow-headed Chipmunk, part; Golden Chipmunk; Side-
stripe Ground Squirrel; Bummer; Trinity Ground Squirrel; Callospermophilus
chrysodeirus trinitatis ; Oitellus chrysodeirus, part; Spermophilus chrysodeirus, part ;
Spermophilus lateralis ; Callospermophilus lateralis chrysodeirus ; Citellus chrysodeirus
trinitatis; Tamias chrysodeirus; Tamias lateralis, part.
Field characters—A medium-sized, ground-dwelling squirrel with conspicuous
stripes along sides of body; whole head more or less deeply yellow or coppery red;
build stout; length of body without tail about 74 inches, with tail about 33 inches
more.
Description.—Adult in fresh late-summer pelage: Whole top of head and hind
neck, orange-cinnamon; cheek and side of neck to shoulder, ochraceous-tawny ; side
of snout, area around eye, ear and spot behind ear, ochraceous-buff of varying inten-
sity; whiskers black. Two black stripes and an intervening buffy white stripe on
each side of body; the whitish stripe longest, extending from shoulder over side of
rump nearly to base of tail; the lower black stripe next in length, the upper shortest
and it and its fellow of opposite side separated by a median band of grizzled light
cinnamon-brown: this band extends from between shoulders backwards to base of
tail, and expands on rump to cover flanks; side of body below lower black stripe,
light buff, obscured by dusky hair-tippings. Upper sides of feet light buff;
83
676 THE MONTHLY BULLETIN.
claws blackish-brown, horn-color at tips; soles of hind feet naked nearly to
heel. Chin and throat and insides of forelegs and thighs buffy white; belly with
hairs extensively slaty brown at base, tipped with whitish; in other words, whitish ©
with much slaty brown showing through. Tail well-haired, flat in form, broadest in
middle portion, tapering somewhat toward end; in color, as viewed from above,
chiefly black, with a margin of ochraceous-buff; there is considerable mixture with
cinnamon-brown toward base, however, and separation of the hairs discloses the
deeper-lying hazel color of their roots; lower surface of tail centrally solid hazel, pal-
ing to ochraceous-tawny at base of tail, then a zone of black, and then an outer fringe of
bright ochraceous-buff. The body side-stripes are sharply defined along their edges,
but at their ends fade out gradually ; also the reddish of head blends by degrees with.
colors of body adjacent.
Color variations—As far as we can see there is no difference in coloration
between male and female, in spite of the extraordinarily bright pattern of coloration
in this species. The young, even third-grown ones, are very similar to the adults in
pattern, the difference consisting only in paler tones of color, especially about the
head. ‘There is, however, considerable change in the depth of coloration with season.
In the spring and early summer the head region is much paler than in late summer
and fall, and there is much other evidence of fading and wear to which the pelage
has been subjected. In June specimens the head is pale cinnamon-buff.
As far as we can determine from the collection of specimens studied there is but
one thorough-going molt each year and this takes place in June and July. The
process is gradual. The exchange of old hair for new begins first on the head and
progresses backwards; but specimens often show a patchy coat, with areas of dense
new hair on the head or back surrounded by old worn hair.
We are unable to make out a distinguishable race from the Tr nity Mountain
region, trinitatis of Merriam, 1901, p. 126, type from “Trinity Mountains east of
Hoopa Valley, California (altitude 5,700 feet).” The characters assigned, of color
and size, are not borne out in our large series of specimens from the Trinity region
as compared with series from the northern Sierra Nevada. There is, however, a
slight tendency towards paling of colors in chrysodeirus at the southern end of the
Sierra Nevada and along their east flank; for example, as shown by specimens from
the east declivity of Kearsarge Pass, west of Independence. ‘This modification is
evidently in the direction of perpallidus.
Measurements.—Average and extreme measurements, in millimeters, of twenty
full-grown specimens from the west slope of the high central Sierra Nevada are as
follows: Ten males: total length, 272 (2538-290) ; tail vertebrae, 89 (75-104) ; hind
foot, 41 (38-43) ; ear from crown, 15.7 (11.0-19.0) ; greatest length of skull, 44.0
(42.2-46.2) ; zygomatic breadth, 26.6 (25.2-28.2) ; interorbital width, 10.4 (9.5-11.1).
Ten females: total length, 266 (243-285) ; tail vertebre, 88 (67-100) ; hind foot,
41 (8944); ear from crown, 16.1 (13.0-21.0); greatest length of skull, 42.7
(41.0-44.1) ; zygomatic breadth, 25.9 (25.0-27.1) ; interorbital width, 10.8 (9.2-11.0).
It would appear from the above figures that in males the tail averages a little
longer than in females. The skulls of old individuals, particularly males, relative age
being estimated by degree of wear on the crowns of the molar teeth, show greatest ~
size, particularly as regards zygomatic breadth and heaviness of rostrum. Old
skulls also show wider brain-case, broader jugals, and stouter postorbital processes. .
Weights.—Average and extreme weights, in grams, of twenty full-grown speci-
mens from the west slope of the high central Sierra Nevada are as follows: Ten
males, 181 (155-218) ; ten females, 199 (136-245). Averages, in’ ounces: males,
about 64; females, about 7.
The heaviest example (245 grams) was a pregnant female. Males average heavier
in the fall, when they are fat, than in early summer.
Type locality—Fort Klamath [mountains near], Klamath County, Oregon (Mer-
riam, 1890, p. 19).
Distribution area.—Upper coniferous belt (Canadian and Hudsonian life-zones,
less commonly down into Transition) along the Sierra Nevada, south as far as
Cannell Meadows, in extreme southern Tulare County; north through the Mount
Lassen country to Mount Shasta, and thence west through the Trinity, Seott and
Salmon Mountains (Mus. Vert. Zool.) to extreme eastern Humboldt County (Mer-
riam, 1901, p. 126); also on the Siskiyou Mountains, along the Oregon border of
western Siskiyou County (Merriam, 1901, p. 126); on the mountain- mass-to the
84
THE GROUND SQUIRRELS OF CALIFORNIA. 677
south of the Trinities, in the vicinity of Yolla Bolly Mountain, where Humboldt,
Tehama and Mendocino counties adjoin; and on the Warner Mountains, in eastern
Modoe County (Mus. Vert. Zool.). The range of the Golden-mantled Ground Squir-
rel in northern California is probably less continuous than indicated on the map
(fig. 24), there being sequestered colonies on detached mountains along with similarly
isolated representations of other boreal animals and plants.
Altitudinally, this squirrel extends regularly to above timber-line, where the moun-
tains are high enough for this, and downwards to the lower edge of the chinquapin belt,
that is, scarcely as far as the yellow pines or Douglas firs. At the farthest south, in
the Mount Whitney region, it has been noted as high as 11,800 feet, while downwards
it was not secn below 7,000 feet. In the latitude of Yosemite, the highest point at
which it was observed was 10,700 feet, and the lowest, Merced Grove of Big Trees,
5,000 feet. In the Trinity region, the lowest occurrence noted was at 4,500 feet
altitude. There is thus a notable lowering of altitudinal limits with increased latitude.
Specimens examined.—A total of 259, from the following localities in California :
Modoe County: ten miles northwest of Canby, 1; Sugar Hill, 11; Parker Creek and
North Fork Parker Creek, Warner Mts., 9; Warren Peak, Warner Mts., 7; Dry
Creek, Warner Mts., 1. Siskiyou County: head of Little Shasta River, northeast
base Goose Nest Mt., 2; Mount Shasta, 10; Kangaroo Creek, 1; Wildcat Peak,
3; Jackson Lake, 5; Saloon Creek Divide, 11; Castle Lake, 2; head of Rush
Creek, 6; South Fork Salmon River, 8. Trinity County: Bear Creek, 11; North
Fork Coffee Creek, 8; head of Grizzly Creek, 5; one-half mile south of South Yolla
Bolly Mt., 8. Lassen County: Hagle Lake, 2; Horse Lake, 1. Tehama County: two
to four miles south of South Yolla Bolly Mt., 19; Mount Lynn, 2. Plumas County:
Mohawk, 1. Sierra County: near Sierraville, 1. Nevada County: Independence Lake,
5. Placer County: Tahoe Valley, 2; Cisco, 13; two miles west of Soda Springs
Station, 1. El Dorado County: Mount Tallac, 1. Mono County: Leevining Creek, 1;
Walker Lake, 1; Bloody Canyon, 1. Tuolumne County: Ten Lakes, 1; Glen Aulin, 1;
Tuolumne Meadows, 4; head of Lyell Canyon, 2; Aspen Valley, 2. Mariposa County:
Vogelsang Lake, 1; Porcupine Flat, 83; one mile east of Merced Lake, 1; near Mono
Meadows, 2; Mount Clark, 1; Merced Big Trees, 5; Hast Fork Indian Canyon, 1;
Chinquapin, 3. Inyo County: Little Onion Valley, 1; Onion Valley, 4; Hockett
Trail (near Carroll Creek), 2; Little Cottonwood Creek, 4; Cottonwood Lakes, 6.
Fresno County: Kearsarge Pass, 5; Bullfrog Lake, 8; Bubbs Creek, 1; Horse Corral
Meadow, 2. Tulare County: Siberian Pass, 1; west slope Cirque Peak, 1; Whitney
Creek, 3; Whitney Meadows, 18; west slope Olancha Peak, 1; Dry Meadows, 1;
Monache Meadows, 7; Jackass Meadows, 14; Sirretta Meadows, 3; Cannell
Meadows, 5.
Of all our ground squirrels the Golden-mantled is the most brilliantly
colored. This rather bookish name for the animal is a translation of the
scientific name of the species, chrysodeirus; the more commonplace
appellations locally employed, ‘‘Copperhead”’ or ‘* Yellow-headed Chip-
munk,’’ serve just as well to set forth the conspicuous feature of
coloration. Because of the bright colors and especially the striping of
the body (see fig. Z0d), this ground squirrel is often called ‘‘ chipmunk ;”’
but the latter name applies to a quite different group of animals which
are slenderly built, agile, with long tails, and more numerous body
stripes which involve the head as well as the body.
The Golden-mantled Ground Squirrel is truly a ground squirrel in
essential features of appearance and behavior as well as structure.
Although it lives for the most part in forested regions, it keeps strictly
on the ground when traveling or feeding, and only ascends rocks or
logs when seeking a lookout station. The species, including its three
subspecies in California, is confined to the higher mountains. One
does not meet with it, in climbing the slopes, usually until well through
the yellow-pine belt. Individuals begin to appear with the firs, and
from there on to the upper limit of timber this species constitutes one
of the most conspicuous features of the life of the forest floor. Here
85
THE MONTHLY BULLETIN.
© Callospermophhis chrysoderus chrysodeirus
© Callospermophilus chrysodeirus perpallidus
© Callospermophilus chrysodeirus bernardimus
8 Ammospermophilus leucurus /eucurus
a Ammospermophilué nelsoni nelsoni
2 Ammospermophilus nelson omplus
DISTRIBUTION MAP
MUSEUM OF VERTEBRATE ZOOLOGY
UNIVERSITY OF CALIFORNIA
Fic. 24.
groups of ground squirrels.
have been examined.
Map showing California distribution of the golden-mantled and antelope
The spots represent localities from which actual specimens
the animals are to be seen scurrying across open spaces to their burrows,
just in front of the mouths of which they almost invariably stop a
moment before plunging out of sight, displaying then to full advantage
their color pattern. If the observer traverses their domain quietly, he
may suddenly discover individual squirrels intensely observing him
from perches on the tops of boulders or logs. There they sit in unosten-
tatious, hunched-over postures, blending so well with the background
that they are often passed by altogether unnoticed. The element pro-
tecting them from observation most, at such times, seems to be their
faculty for keeping absolutely still.
THE GROUND SQUIRRELS OF CALIFORNIA. 679
Rarely do Golden-mantled Ground Squirrels assume the upright
picket-pin pose so characteristic of some others of the species. They
most often maintain crouching attitudes when at rest. When running,
the gait is clumsy, as compared with the chipmunks usually to be seen
close at hand. The tail is rather longer than in others of the smaller
sized ground squirrels, and is more conspicuously displayed, often up
over the back, or, when running, either held vertically or frisked
violently fore and aft. This squirrel seems to be, as a rule, almost
devoid of voice. As far as our own experience has gone, there is only
a single chirp of alarm, not loud nor high-pitched, and even this is
uttered but rarely. One observer (W. P. Taylor, MS) has been
fortunate enough to run across a talkative individual. This animal was
watched as it sat bolt upright on a log uttering a ‘‘ sharp eall note,
to-chick, sometimes varying this to tachack, prr nie Ae Oemeral
squirrel-lke quality’’ was ascribed to these notes. At each utterance
a violent flirt of the tail was given.
Speaking of habitat agai, the Golden-mantled Ground Squirrel
shows decided preference for rocky slopes or forest floors littered with
logs, but at the same time without heavy undergrowth. Open ground
is preferred; yet it keeps out of large grassy meadows, save as visiting
the margins of these where they adjoin the woods. Again we see adjust-
ment so that each of the different kinds of rodents keeps to a separate
forage area without undue waste of energy in competing with
another. In the higher, rougher parts of the mountains we have often
found the Copperheads inhabiting rock slides. Here, as in the other
places, where there are logs or scattered rocks, the object appears to be
to secure protection for their burrows, so that these can be located
beneath heavy objects and thus prove difficult or impossible for badgers,
coyotes or bears to dig out.
The mouths of the burrows vary in diameter from 2 to 24 inches, and
the direction taken is usually steeply down into the ground for a foot
or more. Unfortunately, we have never availed ourselves of an oppor-
tunity to dig out the burrow system of a Golden-mantled Ground
Squirrel. We infer it to be simple and relatively short, for two reasons:
the mounds at the mouths of the burrows are usually small in quantity
of earth composing them; and the big roots, logs or rocks beneath which
the burrows in practically all cases lead, would seem to do away with
the need of an extensive and deeply penetrating system so as to secure
safety from enemies which pursue their prey by digging.
The Golden-mantled Ground Squirrel is a spermophile in the truest
sense of the word; it is preéminently a gatherer and eater of seeds, and
most of its time aboveground seems to be occupied in diligent search
for this sort of food. The cheek-pouches in this squirrel are developed
to a maximum degree, and it is no uncommon thing to see an individuat
returning to its burrow from a foraging expedition with its two pouches
so distended with seeds that the head seems double its ordinary width.
We have counted 636 seeds from the two pouches of one squirrel.
Some seeds identified in cheek-pouch contents saved are: Goose
grass (Galium aparie), rice-root lily (Fritillaria sp.), pentstemon
(Pentstemon azureus), and silver pine (Pinus monticola). In the late
summer and autumn months great activity is shown in garnering
chinquapins, and there seems good reason to believe that large stores
87
680 THE MONTHLY BULLETIN.
of these and various seeds are then housed away in the ground for use
the following spring when the animals come out of hibernation and
food is difficult to find otherwise. One individual had its. cheek-pouches
erammed with fragments of a brown-colored fungus such as forms
bracket-like outgrowths on the bark of dead trees and old logs. Our
experience shows this article of diet to be much sought after by members
of the squirrel tribe generally.
Then, too, the Golden-mantled Ground Squirrel eats meat, and even
carrion, as we can testify from the persistency with which our meat- -
baited steel traps set for coyotes and other carnivores are sprung by
the Copperheads. Indeed, it seems reasonable to infer that this ground
squirrel would lose no opportunity to appropriate to its use the dead
remains of any sort of animal. Around camp sites we have often
received good evidence of the omnivorous nature of the Copperhead’s
diet from seeing them gathering the scattered barley from the ground
where the horses had been fed and then gleaning the scraps of cooked
meat as well as bread crumbs from our own table near by. In one
case a ‘‘Callo’’ came again and again to gnaw at a bacon rind. The
young, but a third grown, show almost as much industry in carrying
away food as do the adults.
That not all the food gathered, over and above what is immediately
eaten, is carried to some definitely located storehouse, is shown by an
observation by W. P. Taylor (MS). On the summit of Cloud’s Rest,
Yosemite Park, a ‘‘Callo’’ was encountered which was so used to the
almost daily visits of people as to have become remarkably tame. It
would run up to within three feet of a person, take the dried fruit
thrown down for it, stuffing its cheek-pouches to capacity, and then run
off just a little ways. After digging out a little hollow in the ground
with its front feet, it placed the fruit therem and proceeded to cover
it up with earth, using its front feet again. Sitting over the spot, it
reached out to gather in additional loose stones until the cache was
effectually concealed. Such hiding places as these are probably usea
only temporarily, at times when an abundance of food is suddenly
available, to be stowed safely from someone else’s reach as soon as
possible, and later reclaimed for more permanent salvage.
The young are born mostly in July, but as early as the last of June
at the lowest altitudes of occurrence, and as late as the first week of
August up near timber line. Young one-half grown were taken on
Cannell Meadows, 7,500 feet altitude, Tulare County, on July 7, 1911;
and young but a third grown were taken at Cottonwood Lakes, 11,000
feet, near Mount Whitney, August 31, 1911. These dates are the
extremes in the considerable series we have for time of appearance of
young. Young come above ground when they are as small as one-
fourth adult size (as determined by weighing). There is but one litter
each year. This probably averages close to five in number. Six
females captured along the central Sierras, of dates June 12 to 28,
contained 5, 2, 5, 6, 6 and 5 embryos, respectively. The number of
mamme (represented by nipples) is either four pairs or five pairs, but
this number is not, as some persons think, any index to the number of
young born.
The enemies of this squirrel probably include most of the carnivores
of*the higher mountains. Hair of a ‘‘Callo’’ was found in the feces
88
THE GROUND SQUIRRELS OF CALIFORNIA. 681
of a Mountain Coyote (Canis latrans lestes) in the Yosemite National
Park. Near Monache Meadows, in the Sierras of eastern Tulare County,
one of the writers saw a Mountain Weasel (Mustela arizonensis) in
full pursuit of a ‘‘Callo’’ across open ground in the full sunshine of
the bright forenoon of August 4, 1911. The squirrel was overtaken
by the weasel, and what happened transpired so swiftly that no details
were observable. A gunshot terminated the episode, and the ‘‘Callo’’
was found already stone dead, with two tooth-punctures on each side of
the nape of its neck.
The Golden-mantled Ground Squirrels hibernate regularly. They
doubtless construct warm, dry nests underground, as individuals have
been seen gathering soft materials and carrying these to their burrows.
In one instance an individual was seen to pick up a piece of brown paper
and after tearing it with its teeth and forepaws, stuff it into its cheeks
and disappear into a burrow (C. L. Camp, MS). By the last of August
these ground squirrels begin to acquire fat, and during September and
October they are simply ‘‘rolling in butter,’’ as the saying goes. This
seems to be in preparation for their long period of dormancy, which
extends from the last of October to the middle of April.
Exact dates of going into, and coming out of, their winter sleep are
not available to us. But in the Yosemite region in 1915 individuals
were seen abroad in the Canadian life-zone commonly up to October 18;
on October 30, in the same zone, but two individuals were seen on the
same ground where very many were noted a month previously; and
none at all were seen on subsequent dates when they were looked for
at suitable altitudes. The estimate of April 15 as near the time of
reappearance in the spring is based on what we have been told by
trappers and forest rangers, and their statements were only from
memory.
Sinee the territory inhabited by the Golden-mantled Ground Squirrel
is practically altogether above the altitudinal limit of cultivation by
man, this species rarely figures as anything worse than a camp-robber
or ‘‘bummer’’ (see fig. 20d). We have heard packers complain of its
proclivities in the way of carrying off grain or provisions from summer
camps in the higher mountains. But the total destruction of property
thus wrought can hardly be formidable, and compensating for it to
some degree must be counted the added animation lent to the mountain
scene by the presence of these pleasing rodents.
INYO GOLDEN-MANTLED GROUND SQUIRREL.
Callospermophilus chrysodeirus perpallidus Grinnell.
Other names.—Sierra Golden-mantled Ground Squirrel, part; Yellow-headed Chip-
munk, part; Callospermophilus chrysodeirus, part; Spermophilus chrysodeirus, part;
Citellus chrysodeirus, part.
Field characters.—Hxactly the same as for the Sierra Golden-mantled Ground
Squirrel, save for pallor of coloration.
Description.—Adult in fresh late-summer pelage: Pattern of coloration and chief
features throughout precisely as in the Sierra Golden-mantled Ground Squirrel, but
general tone of coloration paler; middle of back, rump and sides tending towards
89
682 THE MONTHLY BULLETIN.
ashy, head less richly coppery, and under surface of body and upper surfaces of feet
whiter; under surface of tail medially ochraceous-tawny. Because the lighter colors
are paler in tone, the jet black side-stripes stand out with greater sharpness than in
the Sierran race.
Color variations.—Asg in the Sierra Golden-mantled Ground Squirrel. In some
specimens in fresh pelage the throat is pure white w‘thout a tinge of buff. Half-
grown young just out of their nest-burrows show the characteristic paleness of their
subspecies to as great a degree as adults in new coat. The pallidness of the adults
in old worn breeding dress is greater in degree than in the Sierran race, evidently
due to the greater bleaching effects of the more intense sunlight and dryness to which
the Inyo animals are exposed. The innate paleness of the Inyo race is thus accentu-
ated by external factors. ;
Measurements.—Average and extreme measurements, in millimeters, of twenty full-
grown specimens from the White Mountains, Mono and Inyo counties, are as follows:
Ten males: total length, 268 (260-279) ; tail vertebrae, 92 (80-105) ; hind foot, 40
(388-48) ; ear from crown, 13.4 (11.0-15.0) ; greatest length of skull, 42.9 (42.0—
44.0) ; zygomatic breadth, 26.2 (25.0-26.9) ; interorbital width, 10.0 (9.0-11.3). Ten
females: total length, 264 (254-286); tail vertebre, 85 (78-89); hind foot, 38
(386-42) ; ear from crown, 13.3 (10.0-16.0) ; greatest length of skull, 41.4 (89.6—
42.3) ; zygomatic breadth, 25.9 (25.0-26.6) ; interorbital width, 9.8 (9.3—10.2).
As will be seen from the above measurements in comparison with those given for
the Sierran race, there are no important size differences between perpallidus and
chrysodeirus ; indeed it seems likely that, with large enough series, such discrepancies
as are here in evidence would disappear altogether. The same variations due to age
and sex seem to be present.
Weights.—Average and extreme weights, in grams, vf twenty full-grown specimens
from the White Mountains, Mono and Inyo counties, are as follows: Ten males, 182
(166.5-199.5) ; ten females, 160 (141.0-209.1). Averages, in ounces: males, about
63; females, about 53.
There were no gravid females in this lot. All were taken before August 10 and
so none had become very fat. These facts may account for the lesser weights than
shown for the Sierran race.
Type locality—White Mountains at 10,300 feet altitude, near Big Prospector
Meadow, Mono County, California (Grinnell, 1918, p. 429).
Distribution area.—The upper portions of the arid mountain ranges of extreme
eastern California lying east and north of Owens Valley, namely the Inyo and White
Mountains, and the mountain mass lying southeast of Mono Lake. Northernmost
station, Mono Craters, Mono County (Mus. Vert. Zool.) ; southernmost, summit of
Inyo Mountains east of Lone Pine (Hlliot, 1904, p. 288). Along this extent of
territory the distribution of the animal is, not continuous but is interrupted at the
lowermost gaps between the Inyo and White Mountains and at the extreme head of
Owens Valley. Zonally, this race belongs to Boreal, but it extends down locally as
low even as Upper Sonoran (see fig. 23). In other words, it extends from above tim-
berline down to as low as 7,000 feet altitude (lower edge of pifions), the latter level
for it being recorded from the bottom of Silver Canyon east of Laws. The highest
observed station of occurrence is McAfee Meadow, 11,600 feet, near White Mountain
Peak (Mus. Vert. Zool.).
Specimens examined.—A total of 50, from the following localities in California:
Mono County: Mono Mills, 4; Mono Craters, 1; McAfee Meadow, White Mts., 7; Big
Prospector Meadow, White Mts., 22; Cottonwood “Jreek, White Mts., 1. Inyo
County : Roberts Ranch, Wyman Creek, White Mts.; 2; Silver Canyon, White Mts., 4;
Black Canyon, White Mts., 5; Mazourka Canyon, Inyo Mts., 4.
This is simply a pale desert-range race of Golden-mantled Ground
Squirrel, probably cut off but incompletely from its near relative,
chrysodeirus, of the Sierra Nevada. There can hardly be expected to
be any decided differences in habits between the two; yet the different
“‘setting’’ of perpallidus—exceedingly dry, rocky slopes, with only
sparse timber at best—has left in our minds an impression of distinct-
ness. This only goes to show that we cannot conveniently, nor should
80
THE GROUND SQUIRRELS OF CALIFORNIA. 683
we properly (from a scientific standpoint), consider any animal
altcgether apart from its normal surroundings.
In the Inyo Mountains this squirrel was found by H. S. Swarth (MS)
to range from the level of the lowest pinons in Mazourka Canyon, about
7,500 feet altitude, to the highest summit visited by him, 10,500 feet.
In the White Mountains, east of Laws, the senior author found it to
range down Silver Canyon to as low as 7,000 feet altitude, and here
_ this and the Antelope Ground Squirrel of the lower country overlapped
in their ranges to a small degree. The ‘‘Callos,’’ in such precipitous
canyons as Silver Canyon, were essentially ‘‘rock’’ squirrels, in that
they had their retreats in the slides of shale rock at the bases of the
eliffs and even in the broken rock outcrops far up the canyon walls.
Through and along these they clambered, a bit clumsily perhaps, but
without loss of foothold so far as was seen.
Higher up, on the lofty rolling plateau forming the summit of this
mountain range, the Golden-mantled Ground Squirrels were extremely
abundant along the edges of the stunted forests of foxtail and lodgepole
pines, and even far from timber out on the sagebrush flats, but in the
latter locations there were always near at hand fractured granite out-
erops which afforded safe retreats. Where there were grassy meadows
the animals foraged all over them. It occurred to the observer that here
in the White Mountains there was but this one species of ground squir-
rel and that it therefore had the run of the whole place, as it were,
without meeting with any competitor, as is the case in the Sierras and
elsewhere. This would account for the facts as observed, namely, that
in the White Mountains the Copperheads were extraordinarily abundant
and ranged widely into all sorts of associations.
' Our lines of rat-traps baited with rolled oats brought in many
“*Callos,’’ even youngsters but a third grown, and it was practically
impossible to keep steel traps set during the day, as the bait, consisting
of the bodies of the various birds and small mammals prepared fer
specimens, seemed to be especially attractive to the squirrels. Wherever
the traps were set, they would be searched out and unwittingly sprung
as the squirrels scrambled over them in quest of the bait. It seemec
impossible that the “‘Callos’’ could have located some of the settings
- except through scent, and it is reasonable to suppose that the sense of
smell 7s employed not only in seeking meat but when searching for the
bulbs of certain plants.
Young were out in numbers the last week of July at the 10,000-foot
level, being then one-third to one-half grown. Lower down, in Black
Canyon at 8,000 feet altitude, half-grown young were seen on July 5
(1917) ; and at 10,500 feet altitude, on Cottonwood Creek, third-grown
young were noted on August 8. This shows the usual variation of
appearance of young with altitude, which of course has to do with
advance of the season, and so with temperature.
In Mazourka Canyon, Inyo Mountains, two females, each containing
six embryos, medium-sized and small, respectively, were taken May 19
and 22 (1912). We found no evidence of litters of a larger number
than six; and there is certainly no more than one litter per year.
684 THE MONTHLY BULLETIN.
SAN BERNARDINO GOLDEN-MANTLED GROUND SQUIRREL.
Callospermophilus chrysodeirus bernardinus (Merriam).
Other names.—San Bernardino Ground Squirrel; San Bernardino Spermophile ;
Yellow-headed Chipmunk, part; Spermophilus bernardinus ; Spermophilus chrysodeirus
brevicaudus; Citellus chrysodeirus bernardinus; Callospermophilus bernardinus ;
Tamias chrysodeirus brevicaudus; Tamias lateralis, part.
Field characters.—The same as for the Sierra Golden-mantled Ground Squirrel.
The slight shortness of tail characterizing this race is certainly not a sufficient differ-
ence for. notice at any distance.
Description.—In all pelages: Coloration, as far as we can see after comparing large ©
series of specimens, exactly as in the Sierra Golden-mantled Ground Squirrel. None
of the paleness is apparent such as characterizes the Inyo race. |
Variations.—Of the same sort as discussed under the Sierran race.
Measurements.—Average and extreme measurements, in millimeters, of twenty
full-grown specimens from the San Bernardino Mountains are as follows: Ten males:
total length, 260 (240-278); tail vertebre, 80 (68-90); hind foot, 40 (36-48) ;
greatest length of skull, 43.5 (42.0-45.6) ; zygomatic breadth, 26.6 (25.5-27.6) ;
interorbital width, 10.7 (10.1-11.3). Ten females: total length, 251 (236-271) ;
tail vertebrae, 78 (72-86); hind foot, 388.5 (35-42); greatest length of skull, 41.8
(40.4-43.0) ; zygomatic breadth, 25.5 (24.2-26.8) ; interorbital width, 10.2 (9.7-10.8).
Unfortunately, ear measurements from fresh specimens are not available; but dried
skins look to have decidedly smaller ears than in either the Sierra or Inyo race, this
character being especially noticeable in the young. It will be noted from the above
measurements in comparison with those given for chrysodeirus and perpallidus, that
the body size of bernardinus is just the same as in the others, while the tail length
is decidedly less. This, then, is the character of the subspecies bernardinus, short-
ness of tail; and it shows up well in a series of specimens, even very young ones.
However, this difference in tail length between adults of bernardinus and of chryso-
deirus averages but somewhat less than half an inch, and individual variation brings
overlapping in a certain proportion of specimens. In other words, an extra short-
tailed chrysodeirus might even have a longer tail than an extra long tailed bernardinus.
The race bernardinus is but slightly and incompletely differentiated.
No weights are available for this subspecies.
Type locality—San Bernardino Peak, San Bernardino Mountains, San Bernar-
dino County, California (Merriam, 1893, p. 154).
Distribution.—Restricted to the relatively small area, not more than twenty-five
miles in greatest width, comprised in the higher parts of the San Bernardino Moun-
tains (see fig. 24). Belongs to the Boreal zone and upper part of the Transition.
Hxtends up to the very summit of San Gorgonio Peak, 11,485 feet altitude, and
down locally, as near Bear Lake, to 6,700 feet (Grinnell, 1908, p. 141).
Specimens examined.—A total of 84, from the following loeailties, all in San
Bernardino County, California: San Gorgonio Peak, 2; Dry Lake, 5; South Fork of
Santa Ana River, 14; Sugarloaf Mountain, 2; Bluff Lake, 61; Bear Valley, 2.
Far separated by desert and lowland from the habitat of its near
relative on the Sierras, the Golden-mantled Ground Squirrel of the San
Bernardino Mountains has developed slight peculiarities which make it
recognizable as a distinct race. It has the most restricted range, prob-
ably, of any species or subspecies of ground squirrel in the state. It
seems strange that it should be wholly lacking as an inhabitant of the
San Gabriel and San Jacinto mountains, so near by on either
hand and seemingly of quite similar environment to the San Ber-
nardinos. On the higher parts of the San Bernardino Mountains it
is certainly not on the wane, but thrives greatly, perhaps outnumbermg
all the other members of the squirrel family put together.
92
THE GROUND SQUIRRELS OF CALIFORNIA. 685
In July, 1905, we found the Golden-mantled Ground Squirrels
especially numerous around Bluff Lake, altitude 7,500 feet. Here they
were to be seen all over the floor of the pine and fir woods, foraging
among the chinquapin and deer-brush thickets. None was ever seen
to climb a tree, though individuals were often seen perched motionless
on stumps, logs or boulders. No matter where encountered, they always
sought safety in holes in the ground or in erevices among rocks. They
were notably quiet animals, giving only occasionally a single sharp note
of alarm, or else, rarely, a low chuckle.
Fic. 25. San Bernardino Golden-mantled Ground Squirrel as taken from nest while
dormant during period of hibernation. Note that the animal is curled into an almost
globular shape, with head down and nose snuggled against stomach between fore
and hind feet; tail curled underneath, partly concealing head.
Around Bear Lake the Yellowheads were common through the woods
down to the water’s edge. On the north slopes of Sugarloaf, on
August 22, they were very busy gathering cheek-pouchfuls of seeds of
a lupine, and the fruits of the deer-brush (Ceanothus cordulatus) and
of a reddish-fruited currant (Ribes sp.). Elsewhere they were seen
carrying to their burrows quantities of the green burrs of the chin-
quapin (Castanopsis sempervirens). The burrows usually opened out
-under logs, rotten stumps, or boulders. There was seldom any mound
of earth to mark an entrance.
A female squirrel captured at Dry Lake, 9,000 feet altitude, on
June 22, was found to contain four embryos. The young must have
93
686 THE MONTHLY BULLETIN.
been born generally during the early part of July, in a few cases as
late as early August, to judge from the relative sizes of the young seen
abroad. The first to appear aboveground were noted on July 17 at
Bluff Lake. These were about one-third grown and seemed quite able
to forage independently of their parent. The latter paid no attention
whatever to them, only giving the sharp alarm note if an intruder was
sighted.
Two young ones trapped alive were taken home to Pasadena and kept
in a cage. Early in the autumn one killed the other. The remaining
individual survived for three years, latterly inhabiting a rock-pile in
the yard and ranging freely where he would. Each winter he spent
about seven months, October to April, inclusive, in hibernation (see
fig. 25), with only occasional periods of activity for a day or two during
spells of warm weather. It is interesting to note that this inclination
to he dormant was thus shown strongly at the low altitude of Pasadena,
where the winter temperature scarcely ever reached the freezing point.
There could have been no practical reason for it as regards failure of
food, for a supply was always provided the animal in abundance. The
annual program seems to require the dormant period, and this comes
on at a regular time, and lasts the usual period, whether or not it
happens to be essential to the survival of the individual. It is an
inherited trait of the race.
DESERT ANTELOPE GROUND SQUIRREL.
Ammospermophilus leucurus leucurus (Merriam).
PLATE V.
Other names.—Antelope Chipmunk, part; Antelope Squirrel: Harris Chipmunk ;
White-tailed Spermophile; Charming Spermophile; Ammo; Tamias harrisi; Spermo-
philus harrisii; Tamias leucurus; Oitellus leucurus; Spermophilus leucurus ; Citellus
leucurus vinnulus ; Citellus vinnulus; Ammospermophilus leucurus vinnulus.
Field characters.—A small grayish brown ground squirrel with one white stripe on
each side of body and with a short flat tail nearly always held cocked up over its
rump so as to show the white under side conspicuously. Length of body alone about
6 inches, tail about 24 inches more.
Description.—Adult in winter pelage: General color effect on upper surface from
nose to base of tail light brownish drab, changing on shoulders, flanks and outer
sides of fore and hind legs to light pinkish cinnamon. Close inspection shows a
grizzling. due to variegation of colors on the individual hairs, these being, on middle
of back for example, plumbeous at extreme base, then pale. gray, then black, then
brown, and finally white-tipped; some of the hairs on sides and rump are longer than
the average and black to ends. A sharply-defined narrow white stripe on each side
of body from shoulder to side of rump. Wyelids white; ears and sides of head bufty
white; whiskers black. Whole lower surface of body, from chin to root of tail, silvery
white, the bases of the hairs lead-color. Soles of hind feet densely white haired
forward to tubercles (see fig. 26a), thence to balls of toes naked, and plumbeous in
color in dried specimens; outer sides of hind feet and tops of fore feet tinged with
pinkish cinnamon; feet otherwise dull white; claws blackish brown with pale horn-
colored tips. Tail broadly haired and blunt-ended, narrowed at base; above mixed
black and white, giving an iron-gray effect, but, analyzed in its terminal half, an.
cutermost. white border is seen to be preceded inwardly by a black band, then by a
white band, then centrally by black; toward the root of the tail, above, there is a
tinge of pinkish cinnamon, this overlaid with a grizzling as on the back. Under
94
STATE COMMISSION OF HORTICULTURE Fe ASTEES AV;
DESERT ANTELOPE GROUND SQUIRRELS (AT LEFT); FISHER GROUND SQUIRREL (AT RIGHT).
THE GROUND SQUIRRELS OF CALIFORNIA. 687
surface of tail broadly pure creamy white, with an outer black border around the
terminal half, and succeeding this a white fringe.
Adult in summer pelage: Coat short and harsh instead of long and silky. General
pattern of coloration as in winter, but tone of upper surface more buffy, especially
so on top of head; hairs on whole lower surface pure white to bases (no lead-color) ;
tail as in winter.
Color variations.—The sexes are alike in coloration. The young closely resemble
summer adults save that the pelage is not so harsh. There is some individual varia-
tion in tone of gray on back and in intensity of cinnamon on flanks and shoulders,
but we are unable to find any correlation in these respects with locality. In other
words, we are unable to find any tendency within the range of Ammospermophilus
leucurus in California to form subspecies. ‘The range of the animal is continuous
from the Mexican border to the head of Owens Valley and there are no hindrances to
continuous mixing of breed, such as seem essential to subspecific differentiation in
other ground squirrels.
Fic. 26. Feet of ground squirrels to show extent of hairing on soles and posi-
tion and shape of tubercles. a, Desert Antelope Ground Squirrel; b, Stephens
Soft-haired Ground Squirrel; ec, California Ground Squirrel. Natural size;
drawn from specimens.
The two seasonal coats, winter and summer, are interchanged through a clearly
defined process of molt. That from winter to summer begias as early as
April 23 and continues in different individuals as late as June 18; that
in the fall extends from September 12 to October 23. These dates are as
shown by the specimens available. The spring molt commences on the forehead
and proceeds backwards; the last remnants of the winter coat are to be seen on
the hind neck and rump. in the fall the order is reversed, and the rump first
acquires the new winter pelage, the crown and forehead being the last areas to show
the short harsh summer hairs. The hairs of the tail seem to be involved only in the
fall molt, in other words they are not replaced in the spring when the rest of the
pelage is.
Wear, fading, and contact with alkaline soil bring about some modification in the
tones of coloration. In some cases the tails are dirty light brown and the ends of the
hairs are all curled up as if scorched by heat. In April specimens from the sand-
dunes at the edge of Owens Lake near Keeler, the worn winter pelage shows a
curious yellowish tone, but September examples from the same place, in process
of molt, show the new winter pelage to be normal and exactly like that in specimens
from Riverside County.
We are unable to find any grounds for recognizing a separate race of leucurus
from the Inyo region (vinnulus of Hlliot, 1908, p. 241, type from Keeler, Inyo
County).
Measurements.—Average and extreme measurements, in millimeters, of twenty
adult specimens from Inyo County are as follows: Ten males: total length. 235
(200-235) ; tail vertebra, 61.5 (50-70) ; hind foot, 37.7 (85-40) ; ear from crown,
5.7 (5.0-7.0); greatest length of skull, 38.7 (87.5-40.6) ; zygomatic breadth, 22.3
(21.5-23.1) ; interorbital width, 9.6 (9.4-10.1). Ten females: total length, 211
(200-220) ; tail vertebra, 57.7 (46.0-65.0) ; hind foot, 36.5 (35.0-38.0) ; ear from
crown, 5.5 (4.0-8.0) ; greatest length of elienill 38.1 (37. 1-39.4) ; zygomatic breadth,
221 (20.6—22.9) ; racenonieal width, 9.6 (8.9-9.9).
95
688 THE MONTHLY BULLETIN.
Males seem to be a little larger than females, on an average, with proportionally
longer tails. We are unable to find anything in our material to indicate variation
in measurements with either altitude or latitude within the state of California.
Weights.—Average and extreme weights, in grams, of twenty adult specimens
from Inyo County are as follows: Ten males, 104.4 (94.5-120.7) ; ten females, 104
(83.6-115.0). Average in ounces, for both males and females, about 33.
Type locality—San Gorgonio Pass, below Least of] Banning, Riven Conny
California (Merriam, 1889, p. 20, Stephens, 1906, p. 75).
Distribution area.—In general, the southeastern desert region (see fig. 24). Life-
zone chiefly Lower Sonoran, but extends locally up through Upper Sonoran and eyen
into Transition (see fig. 23). More specifically, the Colorado and Mohave Deserts
(not, however, in some of the sandier or low-lying parts) from the Mexican line
on. the western rim of the Imperial Valley and the vicinity of Picacho on the
lower Colorado River, north to the extreme head of Owens YVailey in the vicinity
of Benton, Mono County (Mus. Vert. Zool.).
Along the western edge of the area inhabited by this squirrel, it extends well up
onto the sides of the confining mountains and often far through the passes, as far as
arid conditions prevail; for example, in San Gorgonio Pass, Riverside County, above
Cabezon, and over Walker and Kelso passes, in Kern County, down the valley of
the South Fork of the Kern River to as far at least as Weldon (Mus. Vert. Zool.),
thus well over the rim of the San Joaquin basin. There are in southern California
at least two outlying colonies on the Pacific side of the desert divides; namely, in
San Jacinto Valley, Riverside County (Grinnell and Swarth, 1913, p. 326), and in
Lytle Creek wash within six miles northwest of San Bernardino, in San Bernardino
County (Mus. Vert. Zool.).
Altitudinally, the species ranges from below sea-level, as at Murnace Creek Ranch,
—178 feet, in Death Valley, up regularly to 6,000 feet on most of the desert moun-
tains which reach that height, and in some instances to 7,500 feet, as at the north
base of Sugarloaf in the San Bernardino Mountains (Grinnell, 1908, p. 141), and
even to 8,500 feet, as near the head of Mazourka Cany on, in the Inyo Mountains
(Swarth, MS).
Specimens examined.—A total of 271, from the following localities in California.
Mono County: Benton, and two miles south of Benton Station, 11. Inyo County:
Laws, 6; Silver Canyon, White Mts., 9; Mazourka Canyon, Inyo Mts., 5; Independ-
ence, and two miles north of Independence, 19; west base Kearsarge Pass, Sierra
Nevada, 4; Lone Pine Creek, 4,500 ft., 10; Carroll Creek, 5,500 ft., and Hockett
Trail, 6,500 ft., near Carroll Creek, 4; Keeler, 81; Olancha, 2; Darwin (fifteen miles,
and two miles, north of), 7; Panamint Mts. (Emigrant, Wild Rose, Hanaupah, and
Johnson canyons), 17; Furnace Creek Ranch, and Triangle Spring, in Death
Valley, 18; Shoshone, 2; Little Lake, 2. Kern County: Weldon, Onyx, and west
slope Walker Pass, 16; one mile east of Warren Station, 1; Mohave, 12. Los Angeles
County : Beuiont 8. San Bernardino County: one mile northeast of Barstow, 1;
Oro Grande, 2; mountains on west side of Colorado River, lat. 35°, 1; Blythe Junc-
tion, 1; five miles below Needles, 1; opposite The N Jeedles, BS Clones Valley,
Bee Victorville! 14; San Bermardiaa Mts. (Cushenbury Springs. Cactus Flat, Doble,
north base of Sugarloaf), 17; Cajon (Lytle Creek) Wash near San Bernardino, 1.
Riverside County: base of San Jacinto Mts., near Cabezon, 7; Snow Creek, near
Whitewater, 5; Vallevista, San Jacinto Valley, 4; Palm Springs, 7; Carrizo Creek
and Dos Palmos Springs, Santa Rosa Mts., 5; Palm Canyon, San Jacinto Mts., 1;
Riverside Mt., near Colorado River, 1. San Diego County: San Felipe Valley, 2;
Grapevine Spring, 1; La Puerta, 2; Vallecito, 2; Jacumba, 1; Mountain Spring, 1.
Imperial County : Colorado River, opposite Cibola, 2; twenty miles north of Picache,
4; eight miles east of Picacho, 2.
The Antelope Ground Squirrels constitute a group distinct in many
ways from all our other species. They are hardly less inhabitants of
the ground, as compared with the tree squirrels and true chipmunks,
but in manner they are more vivacious than any of the other ground
squirrels; they run at a much faster clip and hence can forage at greater
distances from safety refuges. Their coloration is distinctive, too,
gray, with one white stripe along each side of the back, and with the
96
: THE GROUND SQUIRRELS OF CALIFORNIA. 689
under side of the tail brilliantly white. This latter feature is in itself
unique, for it is accompanied by a most striking mannerisin, that of the
almost constant carriage of the stubby, flat-haired tail in an upright
position, held against the back, so that the white under surface shows
as a white ‘‘flae’’ when the animal is scurrying away, much as with the
similarly advertising marks of the cottontail rabbit and antelope; only
with the ground squirrel the effect in catching the eye of the observer
is still further heightened by the way in which it is spasmodiecally
twitched whether the animal be at rest or running. This flickering
beam of white ever holds the attention as long as the squirrel is below
the level of the horizon, and short of its burrow or the concealing tangle
of prickly vegetation which it is so anxious to put between it and its
pursuer.
The race called appropriately Desert Antelope Ground Squirrel
(locally, Antelope ‘‘Chipmunk”’ because of its stripes, small size and.
sprightly manners) occurs broadly over the Colorado and Mohave
deserts, thence north clear through the Inyo region. It shows rather
wide adaptability to the varying conditions in this vast area, more so
than any other desert ground squirrel, and ranges from below sea level,
as on the floor of Death Valley, up regularly to 6,500 feet on the steep
slopes of the desert mountains. It even “‘spills over’’ the confining rim
of the Mohave Desert to the westward, locally, on to the Pacific drainage,
as shown in detail in the accompanying list of specimens and on the
map (fig. 24). Although notably continuous in its range over great
stretches of country, it is not difficult to discover preferences, as indicated
by relative abundance. Level sandy ground is, as a rule, but sparsely
inhabited; and we know of some stretches of desert, such as the floor
of the Coachella Valley northwest of Salton Sea, where none at all
seem to exist, although the species is abundant in the foothills adjacent.
The kind of ground most generally preferred seems to be hard-surfaced,
eravelly wash-fans or hill slopes. Kinds of vegetation present seem to
be immaterial, though clumps of squaw tea, creasote bush, cactus, or
tree yucca characterize much of the territory where the Antelope
Squirrels are most abundant.
Our mention of the above preferences must not give an erroneous
idea as to special nature of the habitat of this species. It may be said
again, for emphasis, that this animal thrives in a great variety of
situations. We have seen it on the mesquite-crowned sand dunes of
Death Valley, there as a companion of the Death Valley Round-tailed
Ground Squirrel; on the sagebrush covered flats at the extreme head
of Owens Valley, in the metropolis of the Stephens Soft-haired Ground
Squirrel; on the creasote hillsides near Little Lake, one of our very
few record stations for the Mohave Ground Squirrel; among the pinons
and granite boulders of the northern section of the Panamint Moun-
tais, then associated with the big Fisher Ground Squirrel; and even
upon the steep rocky slopes of the White Mountains at 7,800 feet alti-
tude, in the same rock slides with the Inyo Golden-mantled Ground
Squirrel! Truly a cosmopolite is the Antelope Ground Squirrel, just
so far as the dry atmosphere of the desert extends; but the coastal fog
and general humidity of the Pacific drainage are almost strictly taboo.
The burrow of this rodent is in nearly all cases situated at the side
of a dense brush-clump or boulder so that protection is afforded from
7—45607 97
690 THE MONTHLY BULLETIN.
predators that dig, such as badgers and coyotes. The mouth of the
burrow is kept open, and is flush with the surface of the ground; and
there is usually no trace of any mound. Sometimes there is a small
pile of fresh earth adjacent to a hole, but this is subject to quick
dissipation by the winds or the much more infrequent rains. The
mouth of the burrow is subtriangular in outline, the flattish base of the
triangle horizontal at the bottom. It is not often cireular, as with
pocket gophers and kangaroo rats, and usually can be recognized accord-
ingly. There is evidence that these squirrels use the burrows of other
rodents, too, such as those of wood rats, kangaroo rats, and even badgers.
And in places where such retreats are afforded, individuals seem to
have their headquarters in the interstices of rock slides. Suffice it to
say that in the Antelope Ground Squirrel we do not find a good digger.
It takes a temperamentally phlegmatic animal to dig effectively. The
‘*Ammos’’ are too fidgety.
This species does not live in colonies in the restricted sense in which
this term should be used, but the burrows are scattered out pretty evenly
over the general territory occupied. There is less of interdependence
between the individuals of this species than in most other ground
squirrels.
In traveling through their domain one secs few of these ground
squirrels as compared with their real numbers. They are adepts at
dodging behind bushes, and at eluding observation by skipping off out
of sight considerably in advance of the intruder. For example, in a
census of animal life taken near Mohave, March 14, 1918, during a
three-hour walk, but two Antelope Squirrels were seen, whereas six
were found to have been caught in a line of rat-traps during the same
length of time. Then, too, the characteristic tracks in the sand on a
quiet day after it has been laid by a norther leave a graphic record of
the multitudinous peregrinations of these active rodents. They can
make more tracks in a given length of time than any other mammal with
which we are acquainted!
Some notes made by the senior author the second week of March,
1918, near Mohave will help to give a clear idea of the characteristics
of the animal under discussion. Nearly all individuals seen would run
very fast.across open spaces between the bushes, but would hesitate a
moment or so when passing through the bushes. When approaching
its burrow each animal would stop stock still just short of the mouth
of the burrow, and watch the intruder intently with head turned to one
side sufficiently so that it could look back past its rump. Meanwhile
the tail was vibrated intermittently as usual. Presently the animal
would dive down out of sight. One was seen to go down into a hole
situated in the side of a mound of sand accumulated about the base of
a very large creasote bush. This hole was one yard from the nearest
upright stem, but was directed downward diagonally toward the root-
system, and it was overshadowed by the radiating branches. The
diameter of this burrow at its mouth was just 40 millimeters (about
one and three-fifths inches). The last that was seen of another squirrel
as he dived for his burrow, he had his tail over his back twitching as
violently as ever. He, too, had hesitated just an instant before the
final plunge.
98
THE GROUND SQUIRRELS OF CALIFORNIA. 691
One individual was surprised eight feet above the ground in a tree
yueca, where he had doubtless been prospecting among the ripe pods
for the seeds. He ran Gown the yucea trunk head for emost, with clearly
audible noise of claws on rough bark. Even in this position the tail
was kept appressed to the rump and was flicked in fore-and-aft direction.
This ability to climb is not exceptional among individuals of this species,
and is quite consistent with the general agility of the animal. Near
Keeler, on the morning of September 25, 1917, six individuals were
seen severally in the teps of sarcobatus bushes evidently gathering the
small, fleshy leaves. At the distant approach of the observer each
scurried to the ground and each had altogether disappeared by the
time he had come up. At Onyx, Kern County, June 21, 1911, one was
seen perched on the top of a fencepost. At Carroll Creek, near Owens
Lake, September 8, 1911, several were seen at different times perched
bolt upright, picket-pin fashion, on isolated boulders out on the mesa.
As a general thing Antelope Ground Squirrels do not have access to
water and they live for long periods without it. Like other typically
desert rodents, they can secure all the water needed in their systems by
chemical elaboration of their food materials. Yet that water is sought
for where available is shown by the following instances: When
camped at a spring near the head of Kelso Valley, Kern County, July
8, 1911, the senior author saw an ‘‘Ammo’’ come without hesitation to
the lowest hoofprints containing water below the spring and drink five
times; each time about ten seconds were apparently occupied in lapping.
At intervals the animal looked around, vibrating his tail the while with
ereat rapidity. At least six other individuals came to drink durimg
that day, arriving through the brush from considerable distances. One
of these, observed closely, was seen to lap hurriedly and briefly eight
times.
Some observations made at the same time and place bear further on
the behavior of this species of ground squirrel. When one is stalked
it will make a dash of ten feet or more to a near-by shrub or rock. If
the observer continues to advance the squirrel disappears down a hole
or under a bush, or else makes another similar dash and stops again. It
then either stands on all fours with its back humped up toward the
intruder and its head turned around so as to watch, or it stands
upright on its haunches, turning more toward the observer. In either
case the tail is held over the back and is wiggled, either antero-
posteriorly or laterally. The tip of the tail, at least, shows no constant
direction of movement. ‘‘ When entering a burrow I saw one individual
drop his tail down behind him and trail it into the burrow instead of
carrying it over his back’’ (Storer, MS). Often when running an
‘‘Ammo’’ will be seen to jump short distances, quite clearing the ground.
‘““T saw one in a tree yucca where I only came to detect his presence
by seeing the shadow of his wiggling tail’’ (Storer, MS). The animals
seem to be able to climb the prickly cactuses and yuccas without
sustaining any serious injury.
The voice of the Antelope Squirrel is unique among the members of
its tribe. It is not a ‘‘bark”’ at all; nor is it a ‘‘squeak.’’ It may be
described as a prolonged mellow rolling trill, weakening or falling in
inflection toward the end. The tone is maintained on about the same
moderately high pitch throughout, though an impression of lowering
99
692 THE MONTHLY BULLETIN.
may be received because of the progressive diminution in volume.
The sound is of a quality to carry well, yet even at very close range it
rarely sounds loud. The direction of the performer is usually hard to
fix. This shifting, ventriloquistic quality goes well with the shimmering
landscape and elusive behavior of the animal, with which it is usually
associated in our experience.
The breeding season begins about the first of Mareh and, in its various
phases, lasts ordinarily until the end of May. At the highest altitudes
the program is evidently retarded some because of the later advent of
warm weather. There is nothing to indicate that more than one litter
is produced each year by one female. The instances of late appear-
ance of young (for example, in August), where not accounted for by
altitude, would seem likely to be due to individual variation in time
of development of the reproductive imstincts or else to abortion or early
death of the first litter. The following is the more or less exact breeding
data given -in the field notes on file in the Museum of Vertebrate
_ Zoology.
The earliest date for embryos is February 20 (1910) near Needles
on the Colorado River; the number of embryos was eight. On March
11 (of the same year), in Chemehuevis Valley, south of Needles, a
female was taken containing five embryos. The weather was yet cold,
ice on standing water at night. It seems to be a rule with the squirrel
family in the desert that the breeding season is so timed that the young
of the year are well grown long before the period of intensest summer
heat.
Mareh 11 to 16 (1918) thirty Antelope Squirrels were trapped or
shot in the vicinity of Mohave. Of these, seventeen were males and
thirteen were females, all adult and in breeding condition. The testes
of the males were huge, measuring up to three-fourths of an inch in
length. The uteri of the females were heavy-walled, but in only one
case were there yet any embryos; one taken March 11 contained five
well-developed embryos. The males were lean; the females all more
or less fat. On March 18 (1914) at Victorville two females were taken,
containing thirteen and fourteen embryos, respectively. On March 27
(1907), at the same place, a female was found to contain eight embryos.
On April 6 (1918), at Olancha, two females contained nine and ten
embryos, respectively ; and on April 12 one was found to contain seven
embryos. On April 24 (1912) at Keeler a female was taken which
contained six embryos.
The average number of young per litter as figured from the above
records of embryos is close to nine, with five and fourteen as extremes.
Stephens (1906, p. 75) considers five to eight as the usual number.
Nelson (1918, p. 443) gives four to twelve. Mearns (1907, p. 301)
records that near Mountain Spring, in May, 1894, ten small young of
uniform size were caught from one hole.
The mamme are generally in five pairs, occasionally in six, rarely
five on one side and six on the other.
The earliest date we have for the appearance of young aboveground
is April 23 (1917) at Furnace Creek Ranch, Death Valley; one young-
ster scarcely one-fifth grown (its weight was ‘put 17.7 crams) was found
wandering about w eakly under a mesquite (see fig. 97). The next date
is May 138 (1908) for third-grown young at Cabezon, and records for
100
¢
THE GROUND SQUIRRELS OF CALIFORNIA. 693
the last week of May are numerous. The latest date is September 4
(1908) for half-grown young at Vallevista, San Jacinto Valley. From
all the facts at hand we would estimate the usual date of birth for this
species to be close to May 10.
By the time they are half grown the young seem to be well able to
forage for food by themselves. No solicitude has been observed on the
part of the parent. The young show themselves to be less shy than
adults, and for this reason it is probable that a large toll is taken by
their enemies during early summer, until the young get sophisticated.
The Antelope Ground Squirrel, according to the data above given,
is the most prolific of all our species of ground squirrels. It can be
inferred from this that existence on the desert, in the mode followed
Fic. 27. Desert Antelope Ground Squirrel, about one-fifth grown, found wandering
about weakly under a mesquite at Furnace Creek Ranch in Death Valley, April 23,
1917. Photographed by J. Dixon. Although very young and feeble this little squirrel
persisted in holding its tail at all times over its back in characteristic Ammospermo-
philus fashion.
by this squirrel, is the most precarious. The factor of high mortality
must therefore be provided against by high birth rate. The category
of predaceous animals which occupy the same territory and which are
sure to prey habitually upon the Antelope Squirrel includes ‘‘snakes,
weasels, foxes, coyotes, badgers, bobeats, and many kinds of hawks”’
(Nelson, 1918, p. 443).
At all the lower elevations, where the winters are not especially cold,
Antelope Ground Squirrels are to be seen abroad at all seasons. For
instance, around Victorville in December and January, 1904-05, and
at Palm Springs in December, 1904, they were to be seen nearly every
day, though they did not seem to be foraging far and wide actively
then as is their wont in March and later. At the former locality on the
coldest windy days none was seen. It is very likely that at higher
places, altitudinally, especially where there is some snow, as at the head
of Owens Valley, these animals hibernate through the coldest months.
101
694 THE MONTHLY BULLETIN.
The fact that there is a special winter pelage, long, full and silky, would
seem to have some meaning as an accompaniment of outdoor activity
at that season. Certain it is, that in texture, the pelage of the Antelope
Squirrels is quite different from that of those species which hibernate
regularly and long. The latter are woolly, with much under-fur. In
the fall and winter ‘‘ Ammos’’ are uniformly very fat. This condition is
probably maintained by drawing upon their food stores, which, to
judge from their persistent industry earlier in the season, must be
extensive. We have never taken the opportunity to dig out the burrows
to see how the seeds and other foodstuffs are garnered. Interesting
facts doubtless await inquiry in this direction.
The Antelope Ground Squirrel is preéminently a gatherer of seeds
and fruits. The two imside-opening cheek-pouches are extensive, doubt-
less on this account. Rarely does an animal captured away from its
burrow fail to show something in them. The following records of
findings of this nature will give a good idea of the diet of the species:
In the tree-yucca belt near Mohave, March 11 to 16, 1918, many of
the squirrels examined were carrying the large flat black seeds of the
tree-yucea (Yucca brevifolia). These seeds were being gathered for
the most part from the ground, where they had fallen from the pod-
clusters overhead. But in a few cases the squirrels were seen up in the
yuceas going right after the ripe pods themselves. The greatest number
of these seeds being carried at one time was seventeen, this in the case
of a male taken on Lee Flat, fifteen miles north of Darwin, September
28, 1917. A female taken in Walker Pass, June 27, 1911, contained mm
its cheek-pouches 98 shelled seeds of juniper (Juniperus califormcus).
A female captured at Keeler, April 28, 1912, had gathered into her
cheek-pouches 178 husked seeds of the salt-grass (Distichlis spicata).
Cactus seeds are frequently gathered, and, in season, the fleshy fruits
are eaten. At Vallevista, San Jacinto Valley, September 4, 1908, the
squirrels were feeding chiefly on the ripe cactus ‘‘pears.’’ The animals
were well stained with the purple juice both outside and in; the whole.
abdominal region was purple in some of the individuals skinned for
specimens. At Cabezon, May 6, 1908, a squirrel was watched in the
top of a cholla cactus eating the tender new-growth buds. The animal
seemed to be able to move about without its feet being injured by the
spines, but upon being shot a thorn was found sticking firmly in the
roof of its mouth.
This squirrel also gathers, doubtless for food, the stems of squaw-tea
(Ephedra), cut into sections, and the leaves of Sarcobatus. Immedi-
ately after rains, when the evanescent aunual vegetation of the desert
starts to grow, sprouting plants of certain species are also gathered.
Judging from the frequency with which Antelope Ground Squirrels
get into meat-baited traps, they must have a decided taste for flesh. We
have also frequently found them eating into the bodies of rodents already
caught and killed in small traps, and in one ease, at least, one of its
own kind was the victim. Nelson (1918, p. 448) says that insects are
eaten when occasion offers.
As for cultivated crops, it is not often that Antelope Ground Squirrels
are to be found in settled regions, and even where they are, they do not
seem to be attracted by the conditions which accompany irrigation.
For example, around Cabezon in San Gorgonio Pass, in May, 1908, the
102
THE GROUND SQUIRRELS OF CALIFORNIA. 695
farmers and orchardists reported that little or no damage was done by
this rodent, although the big Fisher Ground Squirrel was a decided
pest there. The little Antelope ‘‘Chipmunks’’ seemed to keep closely
to the wild land, feeding upon the native seeds and fruits, especially
those of the cactuses.
Still, locally, they may prove noticeably destructive. This was the
case in an almond orchard near Fairmont in northern Los Angeles
County, where in June, 1904, the present authors saw the animals
climbing the trees in the outer rows next to the wild land and carrying
down the as yet unripe almonds. These and the Fisher Ground Squir-
rels were both complained of bitterly by the owner. Again, in Owens
Valley near Independence, on May 7, 1912, a male Antelope Ground
Squirrel was captured, with its cheek-pouches filled with wheat. The
nearest grain field was a quarter of a mile distant. It is thus quite to
be expected that where cultivated land adjoins wild land this species
will make raids upon such crops as prove to its liking.
NELSON ANTELOPE GROUND SQUIRREL.
Ammespermophilus nelsoni nelsoni (Merriam).
Other names.—Nelson Spermophile; Nelson Ground Squirrel; Antelope Chipmunk,
part ; Spermophilus nelsoni; Citellus nelsoni.
Field characters.—A small yellowish-brown ground squirrel with one narrow white
stripe on each side of body, and with a short flat tail nearly always held curled up
over the rump so as to show the creamy white under side. Length of body alone
about 6+ inches, tail about 24 “aches more.
Description.—Adult in summer pelage: General color of upper surface from nose
to base of tal light clay color, brightening toward pinkish cinnamon on shoulders,
flanks, and outer sides of fore and hind limbs; a narrow white stripe on each side
of body from shoulder to side of rump. Wyelids, ears and sides of head dull buffy
white; whiskers black. Whole lower surface of body white, the hairs white to
bases; soles of feet densely white-haired forward to tubercles, thence to balls of toes
naked; upper surfaces of feet white, buff tinged; claws blackish brown with pale
horn-colored tips. Tail as in lewcurus, but upper side near base clay color; under
surface creamy or buffy white centrally. Adult in winter pelage: Coat softer, the
hairs being longer and more silky than in summer. General coloration as in summer,
but tone of upper surface a little darker, and with a fine grizzling due to more
variegated color pattern on the individual hairs. White hairs of lower surface with
extreme bases lead-color.
Color variations.—Sexes alike, as far as we can see. Young colored as in the
summer adults, but pelage finer in texture.
Measurements.—Average and extreme measurements, in millimeters, of twenty
full-grown specimens from the vicinity of Bakersfield, Kern County, are as follows:
Ten males: total length, 226 (210-242) ; tail vertebrae, 70 (61-76) ; h’nd foot, 38.6
(36-40) ; ear from crown, 5.3 (5-6); greatest length of skull, 39.9 (39.0-41.6) ;
zygomatic breadth, 23.2 (21.4—25.0:) ; imterorbital width, 9.9. (9.5-10.4). Ten
females: total length, 221 (203-238) ; tail vertebre, GS (64-74); h‘nd foot, 38.4
(35.0-41.0) ; ear from crown, 5.7 (5.0-6.0) ; greatest length of skull, 39.4 (37.8—
41.3) ; zygomatic breadth, 22.6 (21.5-24.4) ; interorbital width, 9.7 (9.0-10.6).
Males will be seen from the above figures to average slightly larger than females.
The decidedly greater size of nelsoni as compared with lewcurus is at once apparent.
Weights.—Three adult females were found to weigh 141.8, 142.6, and 179.0 grams,
respectively; average, 154.5 grams, or 5% ounces. In bulk nelsoni is thus about
50 per cent larger than lewcewrus.
108
696 THE MONTHLY BULLETIN.
Type locality.—Tipton, Tulare County, California (Merriam, 1898, p. 129).
Distribution.—Occupies the floor of the southern end of the San Joaquin Valley,
and adjacent arid hills and included valleys immediately to the westward (see fig. 24).
Life-zone Lower Sonoran. More specifically, extends from vicinity of Bakersfield
(8 miles northeast) and Poso, in central Kern County, west to the Carrizo Plains
and Cuyama Valley, in southeastern San Luis Obispo County, south to the mouth
of San Hmigdio Creek, 12 miles due east of Maricopa, Kern County, and north to
Huron, Fresno County, and Tipton, Tulare County.
Specimens examined.—A total of 43, from the following localities in California.
Kern County: eight miles northeast of Bakersfield, 32; twelve miles due east of
Maricopa, 5; McKittrick, 8. San Luis Obispo County: Carrizo Plains, 3.
The Nelson Antelope Ground Squirrel is called Antelope Chipmunk
by many of the people who live in the southern San Joaquin Valley.
No distinction is made by them between the present species and the
Antelope Squirrel of the Mohave and Colorado deserts. This is not
surprising when we consider the rather close general resemblance
between the two. When specimens of the two animals are in hand,
tone of coloration alone suffices for distinguishing them. The ground
color of the Nelson Squirrel is distinctly clay color, while that of the
Desert Antelope Ground Squirrel is pinkish buff. In the former, too,
the under side of the tail is creamy buff, while in the latter it is pure
white. In bulk the Nelson is approximately 50 per cent the larger.
The Tehachapi Mountains on the south and the Greenhorn Mountains
to the east help to form a continuous barrier between the range of
these two near-related squirrels. We find the Nelson Squirrel to be
restricted for the most part to the Lower Sonoran life-zone in that
portion of the San Joaquin Valley which lies south of Tulare Lake.
It is notably numerous in the oil districts. The Nelson Squirrel may
be distinguished from all other rodents that occur in this region by
having a very short, flat-haired tail (less than 3 inches in length) and
by the presence of a single white stripe on each side of the body. The
name borne by this species was given to it by its original deseriber
(Merriam, 1893, p. 129) as a recognition of the contributions to mam-
malogy of Edward W. Nelson, now chief of the United States Bureau
of Biological Survey.
During the rainy season many of the smaller streams mn the southern
and western foothills around the San Joaquin Valley cut deep and nar-
row channels, but when the flood waters of such streams reach the upper
plains of the great valley their course is marked by broad washes with
low, perpendicular banks. The silt-bearing waters finally spread out,
forming broad, alluvial fans, and often sink into the thirsty soil before
they reach the lower alkaline plains. The lower reaches of such stream
courses, dry and desertlike most of the year, are the preferred haunts
of the Nelson Ground Squirrel. Here burrows are easily dug between
the hard layers of the stratified banks of the washes, affording safe
retreats from such predators as the coyote and badger. A luxurious
though brief-lived growth of vegetation results from the thorough
natural irrigation of the rich soil of the alluvial fans and the squirrels
are thus afforded an abundant food supply the rest of the year.. Indi-
viduals and even colonies are to be found along the little gullies and
ridges of the upper slopes between the mouths of the streams and the
foothills, while a few may be found along the edges of the alkali ground
104
THE GROUND SQUIRRELS OF CALIFORNIA. 697
of the lower levels; but the metropolis of the species is in the middle
region among the salt-bushes (Atrvplex) which thickly dot these plains.
This ground squirrel is soon driven out when fields come under
cultivation. It clings closely to the wild land and apparently rarely
if ever invades adjoining ground which may happen to be under culti-
vation. Thus in May, 1918, at the mouth of San Emigdio Creek, Kern
County, we found these squirrels quite abundant on three sides of an
extensive alfalfa field which was entirely surrounded by virgin tracts
of the salt-bush (Atriplex), yet during our stay of nearly two weeks,
not a single Nelson Squirrel was observed to enter this field or even to
touch a leaf of the alfalfa.
As usually encountered, the Nelson Squirrels are seen scurrying
rapidly across open places between clumps of salt-bushes, or else, more
rarely, standing straight up to their full height in true ‘‘picket-pin’”’
fashion just before they disappear down their burrows. The normal
mode of travel is by a series of short rapid jumps of from 6 to 12
inches. When approaching a hole leisurely, or when foraging about,
the animals sometimes slow down into a walk.
These squirrels are not early risers, being rarely found abroad until
well after sun-up. At the mouth of San Emigdio Creek, during the
second week in May, Nelson Squirrels began to appear at the entrances
to their burrows in the south-facing overhanging bank of a wash,
between 8 and 8:15 in the morning. They appeared earlier in the day
at this point than elsewhere in the vicinity, doubtless because this bank .
first received the full force of the early morning sun. Ten o’clock
marked the period of greatest activity. The squirrels under observation
disappeared each day between 11:30 and 12 o’clock and were rarely
seen again until 2:30 in the afternoon, when they began to reappear in
the shade of certain dense-foliaged salt-bushes that grew on the brink
of the wash. Although they were frequently seen to bask in the rays of
the early morning sunshine, these squirrels shunned the direct sunlight
at noonday. As early even as 10 o’clock in the morning one female
was seen repeatedly to seek shelter in the shade of a fencepost (J.
Dixon, MS).
The tail of the Nelson Antelope Squirrel, as with the Desert Antelope
Squirrel, is the most conspicuous feature about the animal. When
running, the tail is curved forward over the back, in which position the
creamy under surface is most effectively displayed so that at a distance
one receives the impression that merely a bit of thistledown is blowing
along over the sand. The body of the animal, with its ground-like tone
of color, practically disappears. This illusion is furthered by the
twitching of the tail and by the momentary pauses of the animal which
correspond closely with the usual interrupted flight of a tuft of thistle-
down.
When the squirrel is foraging about on all four legs, or else sitting
up, the tail is held curved forward over the back; in fact, one rarely
sees the tail held in any other position (see fig. 28). At such times the
tip of the tail is often curved slightly upward or outward. When
excited or frightened the tail of the animal is twitched rapidly fore and
aft, but rarely or never sideways. One individual observed at a dis-
tance of ten feet was seen to vibrate its tail intermittently with exceeding —
rapidity, there being half-minute intervals between the periods of
105
698 ‘THE MONTHLY BULLETIN.
vibration. There were from four to six of these periods of vibration
in a series. The tip of the tail would travel only a short distance, less
than a couple of inches, as it was never seen to reach a vertical position
above the animal’s back when the squirrel was standing on all fours.
These squirrels are notably cautious about coming out of their holes;
they were never seen to come out hastily. Furst the nose and then the
eye of an animal would stealthily appear, and then a thorough look
around for possible danger taken, before a squirrel considered it safe
to leave the shelter of its burrow. However, when they do move, their
actions are very sudden, as though they had been undecided just what
to do, but having once made up their minds are off in a whirl of dust.
These rodents are more easily alarmed .by sound than by sight. The
Fic. 28. Young Nelson Antelope Ground Squirrel, photographed by J. Dixon, May
9, 1918, on lower San Emigdio Creek, Kern County. Note how well the general color
of the animal blends with the tone of the background, and yet how strikingly the white
of the under side of the tail shines forth.
eracking of a twig would send them hot-footed to their burrows. Yet
the observer was able to walk up to within thirty feet of them in plain
sight in the open as long as he made no violent motions. By approach-
ing slowly and directly towards the squirrels, it was frequently possible
to get within ten feet when they were sunning themselves at the
entrances to the burrows under the overhanging banks.
The sense of smell seems to be extensively used in the daily life of
these animals. At the close approach of the observer the noses of these
little squirrels were seen to twitch constantly as if in effort to catch the
scent of the stranger. The sense of smell also plays an important part
in locating food. Then again it is used socially. When following each
other about, in and out of the burrows, they often stop and sniff to see
106
THE GROUND SQUIRRELS OF CALIFORNIA. 699
which way the other has gone. Smell serves as a means of identifying
the other members of the same family. Outsiders are quickly detected
and promptly driven away. The members of one family of squirrels
which was closely watched were found to be very sociable, never quarrel-
ing among themselves. The parents were often seen sitting side by side
feeding in perfect harmony (see fig. 29), while at other times this pair
would sit together and rub noses in a very affectionate way. The only
time that they were seen to show fight was when a strange male squirrel
attempted to enter their burrow, and then the male of the pair promptly
put the intruder to flight.
Fic. 29. Adult male and female Nelson Antelope Ground Squirrels, feeding in
uarmony side by side under wholly natural conditions. Photographed by J. Dixon,
May 9, 1918, on lower San Emigdio Creek, Kern County. The openings under the
horizontal layers of the wash banks afforded these squirrels safe retreats. Note the
characteristic Ammospermophilus pose of body and tail.
The alarm note of the Nelson Antelope Ground Squirrel is much
subdued as compared with the clear penetrating trill of the Desert
Antelope Ground Squirrel. In fact, the former is much less frequently
heard at all. While the junior author was watching a family of Nelson
Squirrels at play on the morning of May 8, 1918, an old female was seen
to disappear into one of the numerous holes in the bank. About two
minutes later his attention was attracted by the low, inquisitive chirr
of this same squirrel, which was standing motionless less than ten feet
behind him. This alarm note was repeated five or six times at intervals
of from 30 to 45 seconds. In uttering this note the mouth was opened,
but the effort was not convulsive nor was the thorax greatly contracted.
The note was subdued in tone and probably not audible to human ears
at a distance exceeding one hundred feet. The confidential quality of
the call note reminded the observer very much of the clucking note of
the female valley quail when keeping her young together.
107
700 THE MONTHLY BULLETIN.
Numerous holes in the sides of gullies and in the banks of washes
form the most conspicuous signs of the presence of the Nelson Squirrel.
Tracks and mounds at the entrances to burrows are not as noticeable
as one would expect from the number and size of the animals. Trails
from the burrows to the feeding grounds of this species are usually not
well defined. In one place near the mouth of San Emigdio Creek
these squirrels were obliged to cross a large dusty area in traveling
back and forth between their burrows and their feeding grounds.
Numerous tracks in this dusty spot showed that the squirrels in this
colony did not follow definite trails, but that each individual chose his
own route. In passing around a projecting bank, however, the tracks
were found to converge for a short distance into broad, well-beaten
paths six to eight inches wide.
The favorite location for burrows of this squirrel is, as already stated,
in the sides of banks at the edges of washes or oullies. The burrows
usually enter near the bottom of the bank. The entrances to the
burrows vary from 14 to 8 inches in diameter. The largest holes
are in soft ground beneath horizontal hard strata in the bank and their
large diameter is due at least in part to the weathering or caving in of
the soft earth. The burrows of smallest diameter are found in hard,
level ground at the roots of Atriplex bushes. The entrances to burrows -
in the banks are from six inches to fifty feet apart. These bank burrows
run back in a generally horizontal direction and are interconnected to a
considerable extent under the bank. This was proven by sceing a certain
squirrel, known by sight to the observer, disappear into one hole and
then in a few minutes reappear at the mouth of an adjoining burrow
twenty or more feet distant.
All of the eight burrows dug into by various persons from this
museum have proven to be simply refuge burrows, with only one
entrance; that is, not of the intereommunicating type. Squirrels were
found to reappear in from 5 to 15 minutes after they were chased into
such burrows. These refuge burrows were found to be short, less than
twelve feet in length; shallow, less than three feet in depth; and of
small size, less than two inches in diameter. In three cases the squirrels
were gassed in these burrows and an hour later dug out. Two of the
animals were found dead near the wasteball at the entrance of the
burrow, where they had evidently been overcome by the gas when -
attempting to make their way out.
No nests were found in any of the burrows that were dug out, although
nesting burrows were particularly sought for. Consequently we have
no information to offer regarding this phase of the animal’s life history.
The Nelson Squirrels found near the mouth of San Hmigdio Creek
were found to be moderately infested with fleas. The squirrels were
often seen to stretch out to their full length and roll over and wallow
about in the fine powdery alkaline dust which in many places was an
inch deep under the overhanging banks along the edges of the washes.
Such dust baths, which were frequently indulged in with considerable
evident satisfaction by the squirrels, are likely to serve in keeping the
pelage of the animal clean as well as to discourage the fleas.
Our data regarding the breeding of Ammospermophilus nelson is
scanty. The breeding season appears to be much earlier in this species
than in the case of the Fisher Ground Squirrel in the same region.
108
THE GROUND SQUIRRELS OF CALIFORNIA. 701
The young of nelsoni are apparently all born before the last of April.
None of the numerous females taken in the vicinity of Bakersfield
between April 27 and May 12 were found to contain embryos. A male
one-fourth grown was taken eight miles northeast of Bakersfield on
May 7, 1911, and a half-grown young one was taken at McKittrick on
May 18, 1911. On May 9, 1918, two immature individuals, weighing
100 and 103.3 orams, respectively, were taken at the mouth of San
Emigdio Creek. These, male and female, were thus over two-thirds
grown and were at this time foraging for themselves. These two
youngsters were extremely playful and on several occasions they were
seen to stand upon their hind legs and with their front paws braced
against one another’s shoulders they wrestled and pushed each other
about energetically. The parents of these young squirrels had evidently
east them off to shift for themselves.
Because the California and Fisher Ground Squirrels have increased
and profited by the farming activities of man in parts of the San
Joaquin Valley, it has been suggested that possibly this increase has
tended to crowd out Ammospermophilus nelsoni and therefore restrict
the range of the latter (Taylor, 1916, p. 20). At the mouth of San
Emigdio Creek both nelsoni and fishert were found in numbers. Old
eolonies of fisheri, as shown by their extensive workings, were found
between colonies of nelson. The Antelope Squirrels occupied the
sandy washes and the areas covered by the salt-bush, while the Digger
Squirrels occupied the more open tracts which were covered by a low
growth of foxtail. While there must be a certain degree of competition
as regards food supply between the two kinds of squirrels, this com-
petition is probably no greater than that which exists between the
Nelson Antelope Ground Squirrel and, for example, each of the two
species of kangaroo rats which forage at night for similar food over
the same ground used by the Nelson Squirrels in the daytime. We
found no evidence, in this case, that the Digger Squirrels were driving
out the Antelope Squirrels.
The badger is one of the chief enemies of the Nelson Ground Squirrel.
Many squirrel burrows were found that had been dug out by this animal,
and, since in their refuge burrows. these squirrels have no back door
of escape, capture in such cases must be more or less certain.
On May 19, 1918, a pair of Nelson Squirrels was observed to remain
out in the open and watch a pair of Golden Eagles go through a series
of aerial evolutions overhead, in which, with talons tightly locked
together, the birds looped the loop three times. The eagles were
obviously seen by the squirrels, and the swish of their wings was
plainly heard by the observer, yet the squirrels were not in the least
alarmed. However, when a Red-tailed Hawk flew over, the squirrels
hustled at once into their holes. It was therefore inferred that the
hawks and not the eagles were the active enemies of these small squir-
rels. Coyotes and kit foxes also dig out the squirrels in their burrows
and probably pounce upon a few individuals during the daytime.
In foraging, these squirrels slip along close to the ground, often
stopping in the shelter of a bush or pausing in the open and searching
quietly, with body extended, for small seeds upon which they feed. On
May 6, 1918, an old female which was nursing young was observed for
several minutes at a distance of fifty feet. During this time the squirrel
stood at her full height with body erect, busily munching a green head
109
702 THE MONTHLY BULLETIN.
of alfilaria and keeping a careful watch at the same time upon the
intruder. A few days later a squirrel of this species was seen gathering
dry seeds of the alfilaria. It is difficult in the field to be sure just what
kind of seeds the squirrels are seeking out, since the seeds are too small
to be seen at any great distance even with the aid of binoculars, and
the stomach contents are so finely chewed that it is impracticable to
identify the food constituents.
On one occasion an individual was seen to eat the dried flesh from
the hind leg of a dead kangaroo rat. This sort of provender had been
secured from a near-by meat-baited steel trap. From this incident
we conclude that this species of squirrel is not altogether vegetarian in
its food preferences.
Very little information is at hand regarding the food carried in the
cheek-pouches of this rodent. A specimen taken at McKittrick, Kern
County, on May 19, 1911, had 744 seeds of the alfilaria (Hrodiwm
cicutartum) in its cheek-pouches. No food stores of any kind were
found in the few burrows excavated.
The Nelson Antelope Squirrel is distributed unevenly. It occurs in
abundance at only a few localities. At one of these favored localities,
eight miles northeast of Bakersfield, squirrels of this species were found
scattered over the low hills in little colonies of six or eight individuals
(H. 8S. Swarth, MS). It is believed that there were certain small areas
here that supported at least twenty-five of the squirrels to the acre.
However, they were present to this extent on only a small per cent of
the total acreage inhabited. At San Emigdio “Ranch ten squirrels
represent the greatest number found on any one acre. At McKittrick
the number per acre was thought to be not over five. Taking the entire
range of the species into consideration, there is probably about one
squirrel to every two acres.
Our impression is that on the east side of the San Joaquin Valley
the range of this squirrel is now being rapidly restricted by farming
activities. In 1911, and again in 1918, no Antelope Squirrels whatever
could be found in the vicinity of the type locality, Tipton, in Tulare
County, where it was common in June, 1893 (Merriam, 1893, p. 129).
The first Nelson Squirrel was noted in the 1911 search thirty miles
south of Tipton. The gradual settling up of the country, and the
cultivation of the kind of ground inhabited by this squirrel, has resulted
in the crowding out of the species over much of the eastern part of its
original range. It seems only a question of time when continued
reclamation will gradually restrict and eventually exterminate this
species over the arable portions of the San Joaquin Valley.
The Nelson Antelope Ground Squirrel is at the present time of little
or no economic importance. It inhabits barren situations, apart from
cultivated land. Our opinion is that this squirrel is not likely ever
to become a pest.
LOS BANOS ANTELOPE GROUND SQUIRREL.
Ammospermophilus nelsoni amplus Taylor.
Other names.—Nelson Ground Squirrel, part ; Antelope Chipmunk, part ; Ammo-
spermophilus nelsoni, part.
110
THE GROUND SQUIRRELS OF CALIFORNIA. 703
Field characters.—}Hxactly the same as for the Nelson Antelope Ground Squirrel.
Description.—General coloration in all pelages exactly as in ~elsoni proper, but
clay color of upper surface a trifle paler, more buffy, and white side-stripes less dis-
tinet. Size somewhat greater, especially as regards ears.
Measurements.—Avyerage and extreme measurements, in millimeters, of twenty
full-grown specimens from twenty miles south of Los Bafios, in western Fresno
County, are as follows: Ten males: total length, 246 (234-253) ; tail vertebre, 73
(66-75) ; hind foot, 41 (40-48) ; ear from crown, 7.8 (7.0-9.0) ; greatest length of
skull, 41.8 (41.0-42.7) ; zygomatic breadth, 24.8 (24.0-26.2) ; interorbital width,
10.1 (9.4-10.4). Ten females: total length, 236 (280-248); tail vertebra, 73
(67-78) ; hind foot, 40 (37-48) ; ear from crown, 7.7 (6.5—9.0) ; greatest length of
skull, 41.2 (39.8-42.0) ; zygomatic breadth, 24.3 (23.5-25.5) ; interorbital width, 10.0
(9.2-10.3).
Comparison with the measurements given for nelsoni will show that amplus is
decidedly larger, with especially larger ear.
Weight.—Only one record of adult weight is available, that of an old male, 186.3
grams (64 ounces).
Type locality—Twenty miles south of Los Bafios, Merced County [really near
mouth of Little Panoche Creek in Fresno County], California (Taylor, 1916, p. 15).
Distribution.—Known as yet only from a limited section of the floor of the San
Joaquin Valley within 85 miles south of Los Bafios, in southwestern Merced County
and northwestern Fresno County. lLife-zone, Lower Sonoran.
Specimens examined.—A total of 34 from the following localities in California.
Merced County: Sweeney’s ranch in hills “22 miles south of Los Bafios,” 2. Fresno
County: mouth of Little Panoche Creek, 18 or 20 miles south of Los Bafios, 29;
Hayes Station, B. M. 502, on Panoche Creek, 19 miles southwest of Mendota, 2; one
mile. east of Mendota, 1.
The Los Banos Antelope Ground Squirrel very closely resembles the
Nelson Squirrel, and is doubtless practically identical with that form
in general habits and locality preferences. More thorough exploration
will probably show that the distribution of the two is continuous, in
other words that the Los Banos race has resulted from a northward
extension of the ancestral stock which has allowed the acquisition of
the shght differences of greater size and paler tone of coloration which
characterize amplus.
Along the western rim of the San Joaquin Valley south of Los Bafios
this subspecies is common locally. The type series was taken by R. H.
Beck June 20, 1912, near the mouth of Little Panoche Creek, where the
animals were found occupying holes on common territory with Cali-
fornia Ground Squirrels. In one instance a ‘‘chipmunk’’ was shot at
the same hole with a ‘‘ground squirrel.’’
Near the point where Panoche Creek breaks out of the hills, a few
miles farther south, the last of June, 1918, museum collectors found a
few Antelope Squirrels along roads between barley fields. The cheek-
pouches of the two shot at the edge of such a field were full of barley
grains. The breeding season on both the above dates was long passed ;
young were nearly or quite full-grown. Remains of Ammospermophilus
were found about the mouth of the burrow of a kit fox, evidence of
the identity of one kind of enemy.
The sort of country inhabited by this Ground Squirrel is arid and as
yet to but a small extent under cultivation. Water is not available for
extensive irrigation. The economic status already set forth for the
Nelson Squirrel probably also holds for the Los Bafios race.
111
704 THE MONTHLY BULLETIN.
SUMMARY OF POINTS OF SPECIAL IMPORTANCE FROM
THE STANDPOINT OF GROUND SQUIRREL CONTROL.
From the foregoing account of the natural history of the ground
squirrels of California the following facts and inferences stand out as
seemingly of special importance in connection with the determination
and application of methods of ground squirrel control.
1. Of the eighteen kinds of ground squirrels occurring within the
limits of the state, there appear to be only four meriting any particular
consideration from an economic standpoint. These four are the Cali-
fornia (or Beechey), the Oregon, the Fisher and the Douglas ground
squirrels, here named in the estimated order of importance (see fig. 30).
All the other fourteen kinds are, for the present at least, negligible, in
most of the cases because they inhabit areas not cultivated by man,
2. The Oregon Ground Squirrel is less than half the size of a “‘dig-
ger’’ squirrel, but it is ordinarily present in much greater numbers
per given area within its range (most of Siskiyou, Modoc and Lassen
counties) than is any one of the ‘‘digger’’ squirrels in its range. The
Oregon inhabits open grass lands and hence comes into sharp competition
with cattle interests.
3. The Oregon Ground Squirrel is more of a grass eater than a seed
or grain eater, and the most successful method of poisoning should
involve the selection of an appropriate bait accordingly. It does not
store up food to the extent that the ‘‘digger’’ squirrels do. The Oregon
Ground Squirrel, more than any of the ‘‘digger’’ category, is subject
to a sharply defined period of hibernation, and this involves all the
individuals, of whatever age.
4, The California Ground Squirrel is our species of greatest aggregate
numbers and is the one which is most widely distributed over the
cultivated parts of the state. Its close relatives, the Fisher and Douglas
ground squirrels, are known along with the California as ‘‘digger’’
squirrels; regarding most of the following considerations the three may
be classed together.
5. Because of relatively large size the individuals of the ‘‘digger’’
category are able to inflict serious loss. Adults average 14 to 14 pounds
in weight, and are easily able to consume 4 ounce of dry grain or 2
ounces “of green forage at a meal.
6. On open range and pasture lands these squirrels feed largely on
alfilaria and bur clover, two of the most valuable forage plants in the
state. The squirrels are then serious competitors for subsistence against
the flocks and herds upon which man depends for his own support.
On cultivated ground these squirrels feed upon or: destroy in other -
ways grain and fruit crops to a very large extent where present even
in numbers not above those reached on wild land. The tendency seems
to be to increase to extraordinary numbers on cultivated lands unless
effectively checked by man. This is due both to improvements of food
conditions from the standpoint of the squirrel, and to removal of its
natural enemies by man either purposefully or thoughtlessly.
THE GROUND SQUIRRELS OF CALIFORNIA. 705
7. The food preferences of ground squirrels are strongly in evidence
and vary from species to species, and sometimes within the saime species,
from place to place and season to season. It is common testimony of
those who have practical experience in poisoning ground squirrels that
the Douglas is much more easily handled than the California; in other
words, the former takes the strychnine-coated barley more readily. It
is obvious that the success of any method of control by the use of poison
must depend importantly on the nature of the bait employed. The fact
that in some places the California Ground Squirrel has been found to
pass up barley altogether for the seeds of bur clover suggests a likely
way of improving poisoning methods locally.
8. In the ‘‘digger’’ category of ground squirrels there is evidence that
a greater or less proportion of the population hibernates each winter.
In the Douglas this feature of the annual activity of the animal is
clearly evident, in that the majority, or at the higher altitudes all, of
the individuals disappear for weeks or months together during the
winter season. In the case of the California Ground Squirrel, however,
numerous individuals are to be seen aboveground in the lower country
in favorable weather at any time during the winter. But evidence at
hand goes to show that these active individuals are chiefly young of the
year and that most of the older squirrels are then lying dormant below-
sround, in some extreme cases for as long a period as from August to
February. During this interval, therefore, any method of poisoning,
and probably also of gassing, will obviously be ineffective upon a portion
of the population, and this portion which escapes will reappear at the
beginning of the next breeding season to reinfest the area concerned.
9. Some obstacles to the success of control by the method of gassing
arise through the unequal extent and irregular course of the burrows
of the squirrels. It was found that although the volumetric content
of the burrows of the California Ground Squirrel excavated averaged
5.2 cubie feet, in one case an extreme of 17.8 cubic feet was reached.
This obtained in one of the ‘‘colonial’’ types of burrows in which several
establishments supposed to have been originally separate had come to
be intercommuniecating. It was found that the usual dosage was ineffec-
tual in this case. There is no definite way of distinguishing such
‘“‘eolonial’’ burrows, from surface appearances alone. Then, again, in
some burrows there is an abrupt rise in the underground course of the
burrow, which prevents the onward flow of a gas heavier than air, such
as carbon bisulphid, and the squirrel is not overtaken. In either of the
above circumstances we find a reason for the partial failure of extensive
gassing campaigns with current methods.
10. Ground squirrels reproduce rapidly. In the California the
average number of young in a litter is 7.2, with 4 and 11 as extremes.
There is but one litter reared each year, and the young begin to appear
aboveground about the first of May. The sexes are equally divided in
a given population, and it is believed that each female breeds the first
season of her life, that is, when she is slightly less than a year old, and
that she has an ‘‘expectation’’ of rearing four more litters in case she
lives to die of old age. Thus a population of 10 per acre in March may
be expected to increase to 50 per acre by the last of May. Postponement
of attention by the farmer is a losing proposition. A stitch in time
actually saves nine.
8— 43007 113
706 THE MONTHLY BULLETIN.
11. The general habits of ground squirrels are such that they were
able to hold their own in the face of a host of natural enemies which
habitually preyed upon them before the white man’s advent. ~The
squirrels are eminently successful in the battle for existence. They
inevitably prosper when any natural check is removed.
12. The recuperative powers of ground squirrels are great. It is
shown that if the population of one square mile (if estimated at 640
as in the ease of the California Ground Squirrel) were subjected to two
successive control campaigns, each of 90 per cent effectiveness, there
would still remain six squirrels; these three pairs of squirrels would
theoretically at the end of the third breeding season give rise to the full
normal population of 640, with a good margin for natural death. It
would seem that, if absolute extermination prove not possible over any
large area, eternal vigilance must be exercised to prevent the quick
return of the squirrel population to the danger point. The squirrels
must be looked after like weeds, which have to be dealt with year
after year.
13. Ground squirrels breed upon uncultivated or waste land, from
which they invade the cultivated fields within reach as well as such other
lands as are not already fully populated. There is progressive emigra-
tion of a certain portion of the squirrel population each year, in August
and September, involving chiefly or entirely the young of the year just
coming to maturity. By a process of gradual infiltration, land once
thoroughly rid of squirrels may thus be reinfested from more or less
distant areas of dissemimation. Lands successfully poisoned in the
spring may be found repopulated the following fall from some adjoining
territory.
14. Since the squirrels if not interfered with by man are stopped in
their emigrations only at some natural barrier, it seems clear that control
campaigns should not be limited by political or civil boundaries such
as state, county, district or property lines. Rather should natural
Fic. 30. Diagram showing estimated relative importance, as regards economic status,
of the different species of ground squirrels in California. a, California (Beechey )
Ground Squirrel; b, Oregon Ground Squirrel; c, Fisher Ground Squirrel; d, Douglas
Ground Squirrel; e, all other species of ground squirrels in the state put together.
The estimated ratios are, respectively, 10—5—4—3-1.
114
THE GROUND SQUIRRELS OF CALIFORNIA. 707
barriers be hewn to, such as those of climate, seacoasts, rivers, brush
lands and deserts. The forest ranger in anticipating the sweep of a
potential fire, or in combating any actual fire, outlines his campaign
irrespective of any but those lines which will naturally aid most in
stopping the spread of the conflagration.
15. If “‘drive weeks’’ be advocated, as a popular measure to secure
control locally, the time of the year selected should be fixed in accord-
ance with the optimum chances for success, on the grounds of avidity
of the squirrels for kinds of bait available, minimum natural population
(previously to the time of appearance of the young), and probable
weather conditions.
16. The above general remarks must not be construed as in any degree
intended to discourage the continued energetic application of the best
methods of ground squirrel control now in use. But it is hoped the
facts and inferences set forth will convince the reader that the problem
is not a simple one, and cannot be solved by casual, half-hearted meas-
ures. It is believed that great improvement can be secured both in
devising of method and in mode of application.
LITERATURE CITED.
Baird, S. F.
1857. Mammals of North America; the Descriptions of Species Based Chiefly on
the Collections in the Museum of the Smithsonian Institution. U.S. Pace.
R. R. Expl. and Surv., vol. 8, Part I, pp. xxxiv-+764, 60 pls.
Cary, M.
1911. A Biological Survey of Colorado. U.S. Dept. Agric., Bur. Biol. Surv.,
N. Amer. Fauna no. 33, 256 pp., 12 pls., 39 figs. in text.
Dixon, J. 5
1917. Control of the California Ground Squirrel. Univ. Calif. Agric. Exper.
Sta., circ. no. 181, 14 pp., 3 figs. in text.
Blliot, D. G.
1903. Descriptions of Twenty-seven Apparently New Species and Subspecies of
Mammals. Field Columb. Mus., Zool. Ser., vol. 3, pp. 239-261, 2 figs.
in text.
1904. Descriptions of Apparently New Species and Subspecies of Mammals and
a New Generic Name Proposed. Field Columb. Mus., Zool. Ser., vol. 3.
pp. 263-270.
1904. Catalogue of Mammals Collected by BH. Heller in Osonen California.
Field Columb. Mus., Zool. Ser., vol. 3, pp. 271-321, pls. 38-49, 1 map.
Finley, W. L.
1906. The Golden Hagle. Condor, vol. 8, pp. 4-11, 6 figs. in text.
Grinnell, J.
1908. The Biota of the San Bernardino Mountains. Univ. Calif. Publ. Zool.,
vol. 5, pp. 1-170, pls. 1-24.
1913. A Distributional List of the Mammals of California. Proc. Calif. Acad.
Sci., 4th ser., vol. 3, pp. 265-390, pls. 15, 16.
1914. An Account of the Mammals and Birds of the Lower Colorado Valley with
Especial Reference to the Distributional Problems Presented. Univ.
Calif. Publ. Zool., vol. 12, pp. 51-294, pls. 3-13, 9 figs. in text.
1918. Six new Mammals from the Mohave Desert and Inyo Regions of California.
Univ. Calif. Publ. Zool. vol. 17, pp. 423-480.
Grinnell, J., and Grinnell, H. W.
1907. Reptiles of Los Angeles County, California. Throop Inst. Bull., no. 35, 64
pp., 23 figs. in text.
115
708 THE MONTHLY BULLETIN.
Grinnell, J., and Swarth, H. S.
1913. An Account of the Birds and Mammals of the San Jacinto Area of South-
erm California, with Remarks upon the Behavior of Geographic Races om
the Margins of their Habitats. Univ. Calif. Publ. Zool., vol. 10, pp. 197—
406, pls. 6-10.
Long, J. D.
1912. A Squirrel Destructor. Public Health Reports (U. S. Public Health
Service), vol. 27, no. 39, pp. 1594-1596, 7 figs. on 4 pls.
McCoy, G. W.
1912. Notes on the Bionomics of Rats and Ground Squirrels. Public Health
Reports (U. 8S. Public Health Service), vol. 27, no. 27, pp. 1068-1072.
Mearns, I. A.
1907. Mammals of the Mexican Boundary of the United States. U. 8S. Nat.
Mus. Bull. no. 56, Part I, pp. xv-+530, 18 pls., 126 figs. in text.
Merriam, C. H.
1888. Description of a New Spermophile from California. Annals N. Y. Acad.
Sci., vol. 4, pp. 317-821.
1889. Description of a New Spermophile from Southern California. U. 8. Dept.
Agric., Div. Orn. and Mam., N. Amer. Fauna no. 2, pp. 15-16.
1889. Description of a New Species of Ground Squirrel from the Arid Lands of
the Southwest. U. 8S. Dept. Agric., Div. Orn. and Mam., N. Amer.
Fauna no. 2, pp. 19-21.
1890. Descriptions of Three New Species of the Tamias lateralis Group. U. 8.
Dept. Agric., Div. Orn. and Mam., N. Amer. Fauna no. 4, pp. 17-22.
1898. Descriptions of Hight New Squirrels of the Genera Spermophilus and
Tamias from California, Texas and Mexico. . Proc. Biol. Soe. Wash.,
vol. 8, pp. 129-188. p
1898. Deseriptions of Six New Ground Squarrels from the Western United States.
Proce. Biol. Soc. Wash., vol. 12, pp. 69-71.
1901. Two New Rodents from Northwestern California. Proc. Biol. Soe. Wash.,
vol. 14, pp. 125-126.
1910. The California Ground Squirrel. Circular no. 70, Bureau Biol. Sury., U. 8.
Dept. Agric., 15 pp., 4 figs. in text.
Nelson, H. W. ‘
1918. Smaller Mammals of North America. Nat. Geog. Mag., vol. 38, pp. 3871—
493, 59 col. figs., 29 hft. figs., in text. ;
Richardson, J.
1829. Fauna Boreali-Americana. (London, John Murray), Part I, containing
the Quadrupeds, pp. xlvi + 300, 28 pls.
Ridgway, R.
1912. Color Standards and Color Nomenclature. (Washington, D, C.; published
by the author), pp. 8+ 44, 58 col. pls.
Shaw, W. T.
1916. Ground Squirrel Control. Wash. Agr. Exper. Sta., Pop. Bull. no. 99, 11 pp..
2 col. pls., 4 figs. in text.
Stephens, IF:
1906. California Mammals. (San Diego, West Coast Publishing Co.), 351’ pp.,
frontispiece, 28 figs. in text.
Stewart, G. R., and Burd, J. S. i
1918. Control of Ground Squirrels by the Fumigation Method. Univ.. Calif.
Agric. Exper. Sta. Bull. no. 302, pp. 207—224, figs. 1-3.
Taylor; W. P:
1916. A New Spermophile from the San Joaquin Valley, California, with Notes on
Ammospermoplhilus nelsoni nelsoni Merriam. Univ. Calif. Publ. Zool., vol.
17, pp. 15-20, 1 fig. in text.
116
fave 4
a
hy thee AMG
Pea
PRESSBOARD
N.Y.
Colif.
[- 4
Ww
(=)
Zz
3
é oc
:4
@ uv
aa
LION
_ 3 9088 0