The mammals of Bitterroot Valley, Montana, in their relation to spotted fever

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library

DSSTFliC . 4-

FILE cbPY

Issued August 3, 1911.

U. S. DEPARTMENT OF AGRICULTURE 4-

BUREAU OF BIOLOGICAL SURVEY— Circular No. 82

HENRY W. HENSHAW, Chief of Bureau

,r’jSK

THE MAMMALS OF BITTERROOT VALLEY,
MONTANA, IN THEIR RELATION
TO SPOTTED FEVER

BY

HENRY W. HENSHAW

Chief, Biological Survey

AND

CLARENCE BIRDSEYE

Assistant, Biological Survey

100S37° — Cir. 82—11 - 1

WASHINGTON : GOVERNMENT PRINTING OFFICE : 1911

/

8 5* a a

no. 8 2.

LIBRARY FILE COPY

Issued August 3, 1911.

United States Department of Agriculture,

BUREAU OF BIOLOGICAL SURVEY— Circular No. 82.

HENRY W. HENSHAW, Chief of Bureau.

THE MAMMALS OF HITTERROOT VALLEY, MONT., IN
THEIR RELATION TO SPOTTED FEVER,

By Henry W. Henshaw, Chief, Biological Survey,

and

Clarence Birdseye, Assistant, Biological Survey .

INTRODUCTION.

The present report contains the results of investigations carried
on from March 12 to July 14, 1910, and continued in 1911 in coopera¬
tion with the Bureau of Entomology and the State Experiment
Station of Montana. In addition it embodies numerous data obtained
by assistants of the Biological Survey in previous years.

As has long been known, the so-called spotted fever of many
parts of the Rocky Mountain region is peculiarly virulent in Bitter¬
root Yallev, Mont., and the present investigations were undertaken
for the primary purpose of ascertaining the particular species of
wild mammals in and near the valley which harbor ticks, especially
the form Dermacentor venustus , believed to be chiefly responsible
for the spread of this fever. Incidentally also it was intended to
obtain ticks in various stages of development for determination and
study by the Bureau of Entomology and for experimental purposes.
It was further expected that in the course of the season’s trapping
animals stricken by the fever would be taken which might be made
to yield valuable data regarding the etiology of the disease. But
the untimely death in Mexico of Dr. H. T. Ricketts, who had
planned to carry on these studies, put an end for the season to this
part of the investigation, and, although animals were trapped show¬
ing unmistakable signs of disease, in the absence of experts in this
branch of the work the nature of the sickness could not be determined.

The almost complete restriction of the fever to the western side

of the valley has occasioned much speculation and given rise to
[Cir. 82]

4

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

a theory of its possible connection with some native mammal or
mammals living solely on that side ; but a study of the range of the
mammals of Bitterroot Valley has failed to show that a single
species is restricted to the western side. Nevertheless the two sides
differ physically so widely as to influence greatly the distribution
of mammals. On the west side the mountains rise abruptly, forests
or brush covering much of the land except the cultivated tracts;
while on the east side a strip of rolling, treeless, sage-covered bench
land lies between the river and the mountains. Thus the west side
has a somewhat more humid climate than the east, with heavier
growth of brush, which furnishes good cover for most of the small
mammals, and hence favors the presence of ticks. But on the oppo¬
site or less humid side good “ tick country ” occurs only around
those ranches which nestle close up to the mountains. Ground
squirrels, chipmunks, woodchucks, and pine squirrels — animals
which were found to be the principal hosts of the nymphs and seeds
of the fever tick ( Dermacentor venustus ) — are mainly absent from
the broad strip of sage-covered bench land ; but as this land is now
being rapidly brought under cultivation, some of these small mam¬
mals may be expected sooner or later to occupy it. Hence, though
the east side of Bitterroot Valley is at present less suited as a
habitat for the several wild mammal hosts of the fever tick, a studv
of the habits of the mammals of the west side discloses no apparent
reason why the spotted fever should not in time be carried to the
east side.

In the course of our investigations more than 500 mammals were
collected in and around the valley and 20 species were found to carry
ticks either in the immature or adult stage. The hosts of fever ticks
fall naturally into two groups, those that harbor chiefly adult ticks
and those that harbor the younger stages. In the former class be¬
long mountain goats, bears, coyotes, badgers, woodchucks, and possi¬
bly elk, deer, mountain sheep, rabbits, and domestic stock, as horses,
cattle, and sheep. Those of the second class, mainly rodents, com¬
prise ground squirrels, woodchucks, chipmunks, pine squirrels, mice,
and wood rats.

DOMESTIC STOCK.

Unquestionably the great bulk of fever ticks which become en¬
gorged in the Bitterroot Valley do so on domestic stock. These ani¬
mals are much more numerous on the west side of the valley than on
the east and they obtain the ticks from pasture and other unculti¬
vated land infested bv wild mammals. It is obvious, therefore, that
if the domestic animals in the valley are rendered tick free by dip¬
ping, spraying, or by some other equally effective method, the chances
of the infection of human beings will be vastly lessened.

[Cir. 82]

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

5

METHODS OF DESTRUCTION.

Experiments are now being made in Bitterroot Valley to discover
the most practical methods of destroying the several species of mam¬
mals that act as hosts for the fever tick. Excellent formulas have
been worked out for poisoning ground squirrels and other rodents in
California and elsewhere, but methods which give satisfactory re¬
sults in one region are often less successful in another or when tried
on a different though nearly related species. It is hoped therefore
ultimately to replace the formulas here given by others that will
prove even cheaper and better.

In distributing poisoned grain to kill rodents too much care can
not be exercised to prevent the destruction of game birds and other
valuable species. Except under very exceptional circumstances
poisoned grain should never be sown broadcast, but should be
dropped, a few grains in a place, near the mouths of the burrows, if
for ground squirrels, and under stones, pieces of bark or board, or
in old tin cans, if intended to be eaten by mice and rats.

GAME ANIMALS.

The removal of protection from any of the big game animals —
moose, elk, mule deer, white-tailed deer, goats, and mountain sheep —
would result in their speedy disappearance at the hands of hunters,
but in and around Bitterroot Valley the numbers of game animals
are comparatively small and their range so remote from human hab¬
itations that their destruction, on the ground that some of them
carry ticks, is unwarranted, especially as it would have little or no
effect on attempts to stamp out the fever.

BEARS.

Bears have proved prolific hosts for ticks in the Bitterroot region.
In the past they have been both trapped and hunted, and vigorous
efforts will probably secure what remain. They are successfully fol¬
lowed with dogs and are easily trapped.

FUR-BEARING ANIMALS.

Furs are now so hiirh that if a reduction in the number of fur
bearers is thought desirable, it is necessary only to remove the restric¬
tions on trapping in any given area, when trappers will concentrate
their efforts there and soon diminish the numbers.

WOLVES AND COYOTES.

Full directions for trapping and poisoning wolves and coyotes
are given in Circular No. G3 of the Biological Survey. Scent baits
composed of putrid meat, sperm oil, or any liquid animal oil, asa-

[Cir. 82]

6

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

fetida, and musk or beaver castor, are recommended for trapping.
For poisoning, pure sulphate of strychnine should be used in gelatin
capsules, 3-grain capsules for wolves and 2-grain capsules for coyotes.

WOODCHUCKS.

Woodchucks are so easily trapped and shot that persistent effort
only is needed to rid a locality of them. Very little is known in
regard to baits and poisons for this animal. It is believed that green
corn or carrots treated with the standard strychnine-starch solution
will prove effective. When woodchuck burrows are made in the soil,
and not among rocks, carbon bisulphid is the most certain remedy.
(For method of application see below.)

COLUMBIAN GROUND SQUIRREL.

These squirrels feed so largely on green vegetation during the
summer that they are difficult to poison. They take poisoned grain,
however, freely on their first appearance in spring when green food
is scarce and in August just before entering hibernation. The best
results have been obtained with the following bait :

Clean oats _ S quarts.

Strychnine sulphate _ 1 ounce.

Saccharin _ £ teaspoonful.

Thin starch solution _ 2\ quarts.

Dampen the oats with hot water and drain after a few minutes.
Dissolve the* strychnine in the hot starch solution; mix in the sac¬
charin. Apply to dampened oats and allow to stand at least 48
hours. Spread and dry. Distribute early in morning, scattering lib¬
erally about squirrel holes.

In cultivated lands trapping these squirrels with the No. 1 steel
trap by both “ hole ” and “ surface ” sets is very effective. Traps
should be visited at least twice a day to prevent unnecessary suffering
of trapped animals.

Early in the season before the ground dries the use of carbon
bisulphid as given in Circular 76 is highly recommended.

Crude carbon bisulphid, suitable for killing ground squirrels,
prairie dogs, and other burrowing animals, costs about 8 cents per
pound in 50-pound carboys or drums. It is a volatile liquid and
rapidly loses strength on exposure to the air; hence it should be
kept in tightly corked bottles or cans. It should not be introduced
haphazard, but should be used only in burrows where the animals
have been seen to enter immediately before it is applied, so that none
may be wasted. It should be employed in the following manner :

Half tablespoonful of crude bisulphid should be poured on a piece
of cotton waste or other absorptive material ; this should be pushed as
far as possible down the burrow and the opening closed immediately.

[Cir. 82]

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

7

Bisulphid can be used to best advantage after a rain, when the in¬
terspaces in the soil are filled with water, so that the fumes are less
readily diffused into the surrounding ground.

In colonies where the holes are close together half an ounce of
the bisulphid is enough for each burrow, but in the case of solitary
burrows a full ounce should be used.

As carbon bisulphid is inflammable and the fumes highly explosive,
it should never be opened near a fire or where a person is smoking.

SMALLER SPECIES OF GROUND SQUIRRELS AND CHIPMUNKS.

The two species of chipmunks and the side-striped ground squirrel
feed extensively on seeds and are fond also of grain. They can
readily be poisoned with a preparation of strychnine, starch, and
wheat. The following is the formula :

I.

Wheat _ 1 bushel.

Water _ 1 quart.

Starch _ 2 tablespoonfuls.

Saccharin _ _ _ _ _ 2 teaspoonfuis.

Strychnia (pulverized) _ 2 ounces.

Add the starch, saccharin, and strychnia to the water; heat to
boiling and stir constantly after the starch begins to thicken. When
the starch is fully cooked, stir it into the wheat, every kernel of
which should be coated. A galvanized iron washtub is an excellent
mixing vessel, especially as it is easily cleaned. Either the sulphate
or the alkaloid of strychnia may be used.

During rainy weather it is better to substitute melted tallow for
the starch solution as a coating medium. In this case, the wheat
should first be slightly warmed and the saccharin and strychnine
added, and then the tallow applied, in the proportion of a quart to a
bushel of wheat.

II.

Coarse crackling meal - f quart

Strychnine (alkaloid) - 20 grains (iV ounce)

Chop lard cracklings to coarse meal (containing chunks one-quarter
to one-half inch square). With a salt shaker, slowly add the pow¬
dered strychnine, mixing constantly to distribute it evenly. Add
one-quarter quart of fine crackling meal and mix well, to cover the
strychnine and disguise its bitter taste.

PINE SQUIRRELS.

Shooting and trapping seem to be the most practical methods of
reducing the numbers of pine squirrels, as they do not take poison
readilv.

[Cir. 82]

8

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

MICE AND WOOD RATS.

While the food habits of the several species of mice in Bitterroot
Valley vary considerably, all the species, and also the wood rat, are
fond of grain, and may be readily poisoned with the wheat, starch,
and strychnine preparations given on page 7. The manner of dis¬
tributing the poisoned grain most effectively depends on the habits
of each species, which are briefly outlined in the following pages.

POCKET GOPHERS.

Pocket gophers rarely leave their underground burrows, but they
are easily caught in traps. By following the directions here given,
they may be poisoned with a preparation of strychnine and corn or
other grain, or strychnine in raisins, prunes, or small potatoes.

Dissolve an ounce of strychnia sulphate in a pint of boiling water.
Add a pint of thick sugar sirup, and stir thoroughly. The sirup is
usually scented by adding a few drops of oil of anise, but this is not
essential. If preserved in a closed vessel, the sirup will keep indefi¬
nitely.

The above quantity is sufficient to poison a half bushel of shelled
corn or other grain (corn recommended) . The grain is steeped in hot
water and allowed to soak over night. It is then drained and soaked
for several hours in the poisoned sirup. Before using, corn meal may
be added to take up the excess of moisture.

Dry crystals of strychnine also may be used. They are introduced,
by means of a knife, into small pieces of potato, beet, carrot, or
sweet potato or into entire raisins or dried prunes. A single large
crystal (or several small ones) is enough for each bait. Raisins are
especially recommended because they are easily handled and contain
enough sugar to disguise the bitterness of the poison.

The baits having been prepared, the operator inserts them one by
one into the gopher tunnels. The tunnels may be readily located by
the use of a pointed stick or a prod consisting of a spade handle shod
with a metal point and having a metal bar for the operator's foot
about 15 inches from the point. The prod when withdrawn leaves a
hole through which the bait may be dropped into the gopher runs.
The hole may be covered or left open; no difference in results has
been noticed. The prod saves the labor of digging down to the
tunnel and enables a man in a day to distribute gopher poison to 30
or 40 acres of badly infested alfalfa land or meadow. For loose soils
a pointed stick will answer, but for sod or harder soils the iron-
pointed prod with foot bar is far better.

RABBITS.

Rabbits are more easily poisoned in winter when green food is
scarce and they eagerly eat well-cured alfalfa hay. The formula

[Cir. 82]

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

9

recommended is 30 pounds of chopped alfalfa hay, 1 ounce of strych¬
nia sulphate, and 5 or 6 gallons of water. Sprinkle this solution over
the hay chopped into 2-inch lengths until it is absorbed, then sack
the hay and it is ready for use. It can be distributed in the rabbit
runways, on the snow, or on their feeding grounds. This preparation
will doubtless kill rock conies ( Ochotona ) also if distributed in their
rock slides in spring or placed in their “ haystacks ” in fall.

Chopped fruit-tree primings (2 to 3 inch lengths), treated with
strychnine-starch solution (p. 7), is an effective poison for rabbits.
It has the added advantage of not endangering the lives of birds or
stock.

PORCUPINES.

Porcupines are usually not numerous and are easily tracked on
snow and shot or trapped at their dens. Where their dens are among
inaccessible rocks they can probably be poisoned with strychnine in
potatoes or carrots, of which they are very fend. A dose of the
poison as large as 2 or 3 grains may be necessary. Porcupines are
exceedingly fond of salt and will travel considerable distances to
secure it. Apples, carrots, potatoes, or chopped twigs from fruit
trees (2 inches long) coated with the starch-strychnine solution with
salt added should prove effective.

LIST OF MAMMALS FOUND IN AND NEAR BITTERROOT VALLEY,

MONTANA.

By Clarence Birdseye.

In the following list are mentioned all the species of mammals
known to occur in Bitterroot Valley and the adjacent mountain
slopes. A star before a name indicates that ticks were found on one
or more individuals of the species. It may be added that while no
ticks were found on the particular individuals of a number of species
collected, further investigations may be expected to reveal their occa¬
sional presence on some of them.

For determination of the several species of ticks mentioned in this
paper we are indebted to the Bureau of Entomology.

* MULE DEER.

( Otlocoileus hemionus.)

Mule deer occur more or less commonly on the lower slopes of the
mountains on both sides of the Bitterroot from Missoula south to the
head of the valley, as well as in surrounding mountains and valleys.
Deer occasionally wander down into the fields of the Bitterroot Val¬
iev and I have seen their tracks on the school section at Florence,
In the more accessible parts of their range they seem to be rapidly
becoming scarcer, but on the South Fork of the Bitterroot they are
more abundant this year (1910) than for several years past.

100837°— Cir. 82—11 - 2

10

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

Five individuals were examined about May 19, 25 miles south of
Darby, but on only one of them was a tick found — an adult Derma-
centor albipictus attached to the anus. Ticks were not abundant
in the locality where these animals were taken, and it is probable
that in other situations deer more frequently serve as hosts for ticks.

WHITE-TAILED DEER.

( Odocoileus leucurus. )

White-tailed deer are bottom-land animals, in contrast to the mule
deer, which range principally in the foothills and mountains. They
occur in suitable places along the Bitterroot River from Missoula
to Darby, and also along those tributaries of the Bitterroot Avhose
bottom lands afford them congenial cover. On the creeks they range
well up into the mountains, at least as high as 5,500 feet. The only
specimen examined was taken June 25 near Packers Meadow, Idaho,
and was free from ticks. This may have been due to the fact that
there were very few ticks in that locality.

ELK.

( Cervus canadensis.)

Elk were formerly abundant in the mountains on both sides of the
Bitterroot Valley, but they are now scarce, only a few small bands
and roaming individuals remaining in this part of Montana. A cow
elk shot on May 17 at Lake Como had no ticks on it, although ticks
were numerous where it was shot.

MOUNTAIN SHEEP.

( Ovis canadensis.)

Sheep formerly occurred in suitable localities throughout a large
part of the Bitterroot Mountains and the range east of the valley,
but they are now mainly restricted to higher parts of the ranges about
the head of the valley. None were taken.

MOOSE.

( Alecs americanus. )

Moose were once common in parts of the Bitterroot Valley, and
a few are reported still in the mountains to the east and west, but
mainly on the outside slopes.

* MOUNTAIN GOAT.

( Oreamnos montanus. )

Mountain goats seem to be still fairly common over most of their
range in the Bitterroot Mountains and in the mountains southeast

[Cir. 82]

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

11

of Darby. I shot three in the middle of May on Rock Creek near
Lake Como, and secured records of their occurrence on Bass, Mill,
Blodgett, Sawtooth, Lost Horse, and other creeks entering the Bit¬
terroot from the west. They inhabit the broken precipices along the
creeks at from 5,000 to 7,500
feet altitude.

I believe that in proportion
to their numbers mountain goats
serve more frequently as hosts
for fever ticks ( Dermacentor
venustus) than do any other
wild animals. Of the three in¬
dividuals shot each was infested
with a hundred or more adult
and a few nymphal ticks.

Hunters sav that goats killed at
all seasons harbor ticks, which
are very abundant on the goat
rocks where there are no other
large mammals. Many Derma¬
centor albipictus also were
found on these goats.

FLYING SQUIRREL.

( Sciuropterus alpinus. )

ing squirrels occur
throughout the higher forests of
the Bitterroot Mountains and
occasionally follow the creek
well down into the valley.

Two adult and several young
of this species were examined
and all were tick free. The
number examined is insufficient
to prove a negative, but the noc¬
turnal and arboreal habits of these squirrels may render them
immune from ticks.

* PINE SQUIRREL.

( Sciurus hudsonicus richardsoni.)

Pine squirrels are abundant throughout the coniferous timber of
the Bitterroot Valley and adjacent mountains. Most of those secured
in good “ tick ” country ” were found to be infested with nymphal or
seed ticks, several dozen seeds being taken from one squirrel. Most

[Cir. 82]

Fig. 1. — Flying squirrel ( Sciuropterus al¬
pinus). (About g natural size.)

12

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

Fig. 2. — Pine squirrel ( Scinrus hud-
sonicus richardsoni) . (About \
natural size.)

[Cir. 82]

of these ticks were Dermacentor venus-
tus , but several seeds and nymphs
belonged to the genus Ixodes. Pine
squirrels sometimes enter camps and
houses, and might carry ticks with
them. They are active throughout the
year, living in hollow trees or nests in
the branches. They are readily shot
and trapped and undoubtedly could be
destroyed with poisoned grain or nuts.

* YELLOW-BELLIED CHIPMUNK.

( Eutamias luteiventris. )

These yellow-bellied chipmunks are
common in suitable places throughout
Bitterroot Valley and the adjacent
foothills and up to 4,500 feet on warm
slopes. They are to be found in all
sorts of country excejot the open sage-
covered bench land on the east side of
the valley, and usually occur wherever
the fever tick flourishes. In the spring
of 1910 the chipmunks first began to
emerge from hibernation on March IT,
and by the early part of April were
out in full numbers. In autumn they
were reported as entering hibernation
again about Thanksgiving. Most of
those taken in good “ tick country ”
proved to be infested with nymphs, or
seeds, of the fever tick ( Dermacentor
venustus) . One hundred and twelve
were examined.

* WHITE-BELLIED CHIPMUNK.

( Eutamias quadrivittatus um~brinus.)

The white-bellied chipmunks occur
in the mountains mainly above the
range of the last species. They in¬
habit open rocky hillsides, old burns,
where there is plenty of fallen timber,
and rock slides, from about 3, TOO feet
to 8,100 feet altitude, in the mountains

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

13

on both sides of the valley. This is one of the few small mammals
found on the goat rocks, and may serve as a host for many of the
seeds and nymphs of the fever ticks which in the adult stage feed on
the goats. Twenty-nine of these chipmunks — most of them taken in
poor tick country —
were examined and 1#

only one tick was
found. This was a
nymph of Derma-
centor venustus.

*

COLUMBIAN GROUND
SQUIRREL.

( Citellus columManus.)

Columbian ground
squirrels (commonly
called “ picket pins”)
are a b u n d a n t
throughout the whole
length of the valley
and from the river
well up into the
mountains on both
sides. They were
taken on Sweeney
Creek up to 7,000
feet. I believe that
on the whole they
are very much more
numerous on the west
side of the valley,
for they are practi¬
cally absent from the
wide belt of rolling
sagebrush benches on
the east side. In
the valley they seem
most numerous in
stony fields, although
abundant also in
meadows, hayfielcls, and open pine woods. In the mountains they
prefer open-timbered southern slopes. They usually hibernate late
in August and begin to emerge from hibernation toward the end of
March. They were out in full force by the 10th of April. Between

[Cir. 82]

Fig. 3.— 1, White-bellied chipmunk ( Eutamias quadrivit-
tatus umbrinus ) ; 2, yellow-bellied chipmunk ( Eutamias
luteiventris). (About | natural size.)

14

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

Fig. 4. — Columbian ground squirrel

( Citellus columbianus) . (About §
natural size.)

[Cir. 821

150 and 200 u picket pins ” were
examined, and practically all those
taken in good 66 tick country ” were
found to serve as hosts for the
younger stages of Dermacentor
yenustus. On many of them were
several dozen nymphs or seeds ;
from one, 62 nymphs were taken,
and from another over 100 seeds.
No adult ticks were found on them.
It is probable that this ground
squirrel raises more young fever
ticks than does any other species,
possibly more than all other species
of animals combined. Nymphs and
seeds were found on ground squir¬
rels taken from under stables and
unoccupied cabins, and it is prob¬
able that they often drop engorged
ticks under such buildings. The
fact that practically 100 per cent of
these squirrels artificially infected
with spotted fever in captivity
have contracted the disease in mild
form is significant.

One of the most important and
fundamental steps in the control of
the fever is unquestionably a deter¬
mined and concerted effort to
lessen the number of picket pins,
especially in pastures and around
dwellings. These animals are so
destructive to crops that any ex¬
pense incurred in destroying them
will be well repaid by the resulting
freedom from their depredations.

* SIDE-STRIPED GROUND SQUIRREL.

( Callospermophilus lateralis cinerascens.)

The little side-striped ground
squirrels are abundant on the lower
slopes of the mountains on both
sides of Bitterroot Valley through¬
out its length. They seem to prefer

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

15

warm rocky slopes and the vicinity of small settlements in the foot¬
hills. They were especially abundant around Lo Lo Hot Springs and
near the construction buildings at Lake Como. They are true ground
squirrels and hibernate at an earlier date
than the chipmunks, usually about the
1st of September, reappearing in March.

They live largely on seeds and grain and,
when necessary, can be readily poisoned.

Under favorable circumstances tliev serve
as hosts for ticks, and from four out of the
five specimens captured at Woodman were
taken nymphal and seed ticks of Derma -
cent or venustus.

*

WOODCHUCK.

( Marmota fla vir enter. )

Woodchucks are generally distributed
along both sides of the valley and in the
adjacent foothills. They are especially
abundant in rock piles and around vacant
buildings along the valley’s edge. From
one rock pile in a hayfield near Florence
I took 15 woodchucks ; and from under the
unoccupied buildings on the ranch at the
mouth of Bass Creek G specimens were
taken. The first one was noted on March
24, and most of them had emerged from

i

hibernation by the end of the month. By
the middle of August most of them had
again “ holed up.” About 25 of these ani¬
mals were examined for ticks, and it was
found that they commonly serve as hosts
for nymphs and seeds of Dermacentor
venustus. On one were found two adults
of this species; and adults were found to
attach and engorge on woodchucks in cap¬
tivity. It would probably not be very difficult to exterminate these
harmful rodents in the cultivated fields and around ranches.

Fig. 5. — Side-striped ground
squirrel ( Callospcrmopliilus
lateral is cinerasccns) .
(About | natural size.)

HOARY MARMOT.

{Marmota caligata.)

These big mountain woodchucks, hoary marmots, or “ whistlers,”
occur mainly above timberline in the Bitterroot Mountains, and are
not abundant there. None were examined.

[Cir. 82]

16

MAMMALS IN' THEIR RELATION TO SPOTTED FEVER.

HOUSE MOUSE.

(Mils musculus.)

House mice are common in the fields and brush as well as in and
around farm buildings in the valley, but none were examined for
iicks.

* WHITE-FOOTED MOUSE.

(Perompscus maniculatus artemisicv.)

The white-footed mouse is probably the most generally distributed
mammal of the valley, and occurs throughout its entire length and

from the river well up on to the mountains. It
was taken in every sort of country — under fallen
logs, on sage-covered benches, on hot, rocky pine-
covered slopes, on cold, damp slopes, in houses and
stables, in damp meadows, and in dry fields. They
are strictly nocturnal, live mainly on seeds and
grain, and are active throughout the year. As
most of these mice were taken in guillotine traps,
any ticks which might have been on them would
in most cases have become detached before the mice
were found. One partially engorged Dermacentor
vemistus nymph was, however, taken from the ear
of one of these mice caught in a hayfield.

* WOOD RAT.

( Neotoma cincrea.)

Wood rats, pack rats, or mountain rats occur in
the mountains and along both sides of the valley
for practically its whole length. They are to be
found in many cf the unoccupied cabins near the
foothills; and I have seen their signs in rock slides
up to 7,500 feet. They are nocturnal, nonhiber¬
nating animals of rather omnivorous food habits.
fig. 6.— white-footed Green leaves, flowers, fruit, seeds, grain, nuts, and

mouse ( Peromyscus ' , „ , „ ' .

maniculatus arte- almost any cooked tooci irom the pantry are ac-
misice) . (About i ceptable to their taste. Although only one tick,

natural size.) . . . . ‘ „

a nymph (genus unknown), was taken from a
wood rat, it is probable that under some circumstances they occa¬
sionally harbor fever ticks in the young stages.

[Cir. 82]

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

17

Fig. 7. — Wood rat ( Neotoma cincrea ),
(About \ natural size.)

[Cir. 82]

RED-BACKEI) MOUSE.

( Evotomys idahoensis. )

The recl-backecl mouse is com¬
mon in damp mountain woods
and along streams well down
into the valley. No ticks were
found on the few specimens ex¬
amined.

* MEADOW MOUSE.

( Microtus modest us. )

These large dark meadow mice
are common in the meadows
along both sides of the valley.
On the Densmore Ranch, 3 miles
west of Florence, they were very
abundant in a rocky run-down
hayfield used for pasturing
horses. Most of those taken had
been dead long enough for any
ticks which might
have been on them
to detach, but on
three which were
examined while
still warm three
partially en¬
gorged nymphs
of Dermacentor
were found. The
natural food of
these mice is
green vegetation,
but they are fond
of seeds and
grain and can be
poisoned very
readily. They do
not hibernate and
can best be poi¬
soned in winter
when green food

is scarce.

Fig. 8.— Red-

backed mouse
(E v o t o m y s
idahoensis).
(About | natu¬
ral size.)

18

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

GRAY MEADOW MOUSE.

( Microtus nanus canescens.)

This species of meadow mouse occurs in grassy depressions, on
benches, and in upland fields, as well as in marshes and meadows
in the valley bottoms. A few were taken, but none were examined

1. 2. 3.

Fig. 9. — 1, Gray meadow mouse ( Microtus nanus canescens ) ; 2, common meadow mouse
( Microtus modestus) ; 3, long-tailed meadow mouse ( Microtus mordax). (About |
natural size.)

for ticks. In habits they differ very little from the darker colored
modestus , with which they often occur.

LONG-TAILED MEADOW MOUSE.

( Microtus mordax.)

These mice occur principally in the mountain meadows and along
creeks down into the edges of the valley. They are usually not very
numerous or of much economic importance except as food for hawks,
owls, weasels, foxes, and wild cats. They feed mainly upon green
vegetation, and are more partial to water and wet ground

[Cir. 82]

19

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

than the other meadow mice. In winter they are active under the
deep snow.

M USKRAT.

( Fiber zibethicus osoyoosensis.)

Muskrats were formerly common in most of the sloughs and ponds
in the valley, but the extremely high price paid recently for their
pelts has led to a great reduction in their numbers. One was shot,
but no ticks were found on it. Their aquatic
habits may exempt them from such pests.

BEAVER.

( Castor canadensis.)

Beavers occur in the Bitterroot River and
on Lo Lo and other creeks, but they are very
scarce. None were examined, but it seems im¬
probable that they would be attacked by ticks.

POCKET GOPHERS.

( Thomomys fuscus.)

Pocket gophers are common over most of
the valley and in mountain parks and mea¬
dows. Specimens were taken on Ambrose
Creek and west of Florence, but no ticks were
found on any of those examined. They prob¬
ably do not serve as an important host for the
fever tick, as their lives are spent almost
entirely underground. Still ticks are occa¬
sionally found on gophers in other localities.

Pocket gophers do considerable damage to
crops, especially to garden vegetables, or¬
chards, and nurseries, but are easily poisoned
or trapped.

JUMPING MOUSE.

(Zap us princeps.)

Fig. 10. — rocket gopher

The jumping mouse occurs in suitable (Thomomys fuscus).

places throughout the valley and lower parts (About i natural size.)

of the adjacent mountains. Only a dozen specimens were secured,
and although none of them had ticks on them, it is probable tlrat
they sometimes serve as hosts for nymphs or seeds. Unlike other
mice in the valley, they hibernate in winter, denning up with the first
hard frosts. They live mainly upon seeds of grass and other plants,
and are fond of rolled oats and any of the small grains.

[Cir. 82]

20

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

*

PORCUPINE.

( Erethizon epixanthum.)

Porcupines occur sparingly in the mountains on both sides of the
valley and occasionally wander down into the bottoms. On a por¬
cupine caught in an unoccupied cabin at Elk Lake (on Bass Creek)

there were two partially engorged adult ticks. These
ticks were lost, but they looked like Dermacentor.

*

ROCK cony; pika.

(Ochotona princeps.)

Pock conies, or u rock rabbits,” 1 as they are some¬
times called in the Bitterroot, occur in the rock slides
in the higher parts of the mountains on both sides of
the valley. Practically all of the 12 examined were
infested with seeds, nymphs, and adults of Ixodes ,
but none bore fever ticks.

*

SNOWS HOE RABBIT.

(Lepus bairdi.)

Snowshoe rabbits occur in the mountains and in the
brushy and timbered parts of the valley. Three spec¬
imens were examined for ticks and on two of them
were found over 1,000 seeds, nymphs, and adults of
the rabbit tick ( II oemapliy satis leporis-palustris) .
From each of these two, also, an adult fever tick was
taken.

WHITE-TAILED JACK RABBIT.

( Lepus campestris.)

Jack rabbits are common in open country on the
east side of the vallev south at least to Darby. None
were seen on the west side, although they occasionally
occur there. No specimens were taken, but like other
rabbits they are known to serve commonly as hosts
for ticks.

* COTTONTAIL.

( Sylvilagus n uttalli. )

Cottontails are common in brushy places in the Bitterroot Valley
from the river well up into the foothills. Although several were
shot in a locality badly infested with ticks, none harbored the pests.

1 Tlie name “rock rabbit” is applied also to tlie cottontail of the valley, and
more properly, as it is a rabbit and also lives commonly among rocks.

[Cir. 82]

Fig. 11. — Jump¬
ing mouse
( Zopus prin¬

ceps). (About
I natural size) .

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

21

One shot near Stevensville in September, 1008, by Vernon Bailey
was well covered with ticks, some of which were identified by Mr.
Bishopp and later by Mr. Banks as
Ixodes diversifosus. The fever tick also
was found on four specimens.

0

MOUNTAIN LION.

( Fclis Jiippolestes.)

Mountain lions occur sparingly in the
mountains on both sides of Bitterroot
Valley. N one were taken.

CANADA LYNX.

( Lynx canadensis. )

Canada lynxes occur in the mountains
on both sides of this valley and occa-
sionally wander down to the river, but
persistent trapping during the last three
years has greatly reduced their numbers.

None were taken.

BOBCAT.

( Lynx uinta.)

Bobcats occur occasionally along the

t J CD

edge of the valley, but none were taken.

WESTERN RED FOX.

( Vulpes macrourus. )

A few cross- foxes and rarelv a silver
gray are caught in the mountain valleys around the head of the
Bitterroot, but they occur rarely, if at all, in the bottom of the valley.

GRAY WOLF.

( Canis Occident alls. )

Wolves are said to pass occasionally through the Bitterroot V al¬
ley. None were taken.

«/

* COYOTE.

( Canis lestes.)

Until the last year or two, coyotes were common in the valley
throughout its length, but persistent hunting and trapping have

[Cir. 82]

Fig. 12. — Rock cony ( Ochotona
princeps). (About \ natural
size) .

22

MAMMALS IN THEIR RELATION TO SPOTTED FEVER.

recently reduced their number considerably. On one caught in an
orchard on the Densmore ranch, near Florence, in May, there were a
number of adult fever ticks. No other covotes were taken.

* BLACK BEAR.

( U rsus american us. )

Black bears are rather common in the mountains on both sides of
the valley, and they occasionally wander down to the river. Trap¬
pers say that the bears are usually much infested with ticks, and I
found several dozen specimens of Dermacentor venustus on a bear
shot near Woodman on June 30.

GRIZZLY BEAR.

( U rsu s liorri bilis. )

Grizzly bears are now rare, but occur in the higher parts of the
mountains on both sides of the valley. None were taken; but as the
black bear frequentty serves as a host of the tick, it is natural to sup¬
pose that the grizzly does also.

SKUNK.

( Mephitis h udsonica. )

Skunks occur in the valley, and, although I took none, records of
them were secured at Lo Lo. Stevensville, and Corvallis. In other
localities skunks frequently serve as hosts for certain species of ticks,
and it is probable that they occasionally do for fever ticks in the
Bitterroot.

* BADGER.

( Taxidea taxus.)

Badgers are plentiful in the valley throughout its length and
from the river up to at least 5,600 feet in the mountains on both
sides. Only one specimen was taken — near Florence on April 5—
and on it was found one dead adult male Dermacentor venustus .

OTTER.

( Lutra canadensis. )

A few otters wander along the Bitterroot River and some of its
principal tributaries, but they are rarely taken.

* WEASEL,

( Putorius arizonensis. )

Weasels occur in the valley but are not common. In the moun¬
tains they are said to be abundant. On a weasel shot in a rock
slide inhabited by conies on Bass Creek June 15 were found four
adult ticks of the genus Ixodes.

[Cir. 82]

MAMMALS IN THEIR RELATION TO SPOTTED EEVER.

23

MINK.

( Lutreola vison cnergumcnos.)

Minks occur sparingly along the Bitterroot River and some of its
principal tributaries. None were examined for ticks.

FISHER.

( M ustel a penna n ti. )

Occasionally fishers are taken in the mountains on both sides of
the valley, but I secured none.

* MARTEN.

( Mustela c. origenes.)

Martens are rather plentiful in the mountains on both sides of
the Bitterroot River and afford one of the staple furs of the region.
From one caught early in March on Bass Creek a species of Ixodes
was taken.

WOLVERENE.

( GuJo luscus.)

An occasional wolverene is caught by trappers in the mountains
around the valleys, but they are becoming rare.

COMMON SIIREW.

( Sorex personatus.)

These little shrews occur in the grass-grown depressions on the
benches on the east side of the valley and were found also in a dry
hayfield southwest of Florence. None were examined for ticks, and
they are probably too small to harbor anything but seed ticks.

dusky shrew.

(Sorcx obscurus.)

These shrews are common in damp meadows and swamps through¬
out the valley up to at least 3,700 feet. Many specimens were ex¬
amined, but no ticks found on them.

WATER SHREW.

( Ncosore.r na vigator. )

Water shrews occur along the creeks from well up into the moun¬
tains down to the river. It is highly improbable that they serve as
tick hosts.

[Cir. 82]

24

MAMMALS IN THEIR RELATION TO SPOTTED FEVER,

LITTLE BROWN BAT.

{My otis lucifugus.)

These little brown bats are common in the valley and spend the
day in crevices, in bridges, or buildings. Although 20 or more
specimens were examined, none were found to be tick infested.

SILVERY- HAIRED BAT.

( Lasionycteris noctivagans. )

Three of these dark-colored bats were shot, June 19, 2J miles south¬
west of Florence.

BROWN BAT.

(Eptesicus fuscus.)

Only one of these bats was shot.

[Cir. 82]

O

N