The prairie dog of the Great Plains

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PHE PRAIRIE DOG OF THE GREAT PLAINS

BY

C. HART MERRIAM,
Chief of Division of Biological Survey.

[REPRINT FROM YEARBOOK OF DEPARTMENT OF AGRICULTURE FOR 1901.]

CONTENTS.

Introduction .25 5.25.24 Soeccce bs oe ee b oodaen ete ee ee eee
General habits of prairie dogs :.2. 2. .:s..2s.2-+ 25-8 ane: - ee
Timeé.of birth:and number of young:.2-....'. 2... 2-2. -} - see eee
Mounds and burrows : oo... 2. s.252 022 8s2 202 tenses acne eee
Natural enemies... oo. 2252 oc seats hens bona eee
Recent increase and spread of prairie dogs .--.-..... 2.5252. uae eee eee
F000 5.22 222 sees Sos dais Sees be ee Se ee oe ee
Destructiveness +. ..5. 2.2: 24h ih a. be) sc batine soe eee
Popular interest in the destruction of prairie GOO8 Lt Shad. c- oe 5 ee eee
Methods of destruction. ....0..... a GRU Ss ee ee
Obstacles and difficulties of exterminatyaai f;4!. foc... 2.222 eee eee none ee
Prairie dogs on Nantucket C4334) 4 8corg. oie ae ee ee
ILLUSTRATIONS:
PLATES.
PiaTE XXII. The plains prairie dog ( Cynomys ludovicianus).........-.------

XXIII. Mounds of the plains prairie dog: Fig. 1.—Normal mound in
new ground (alfalfa field). Fig. 2.—Mound repaired by scrap-
ing up earth from the outside. Fig. 3.—Inside of rim of mound,
showing nose marks., 2. .f..22...6-..22868 soe

XXIV. Mounds of the plains prairie dog: Fig. 1. Senrcend in flooded
ground, showing protection from rains. Figs. 2 and 3.—New
mound in alfalia field .. 2.30. 222.) seeeewes een < oe en

TEXT FIGURES.

Fig. 24. Distribution of plains prairie dog (Cynomys ludovicianus)....-... ---
25. Prairie-dog DULTOW =. « «cases sone osiges acee 4 eee ss oes ae

II

THE PRAIRIE DOG OF THE GREAT PLAINS.

By C. Harr Merriam,

Chief of Division of Biological Survey.
INTRODUCTION.

In crossing the United States by any of the transcontinental railways
the traveler who looks out from the car window on the second day west-
ward from Chicago is sure to have his attention arrested by colonies of
small animals about the size of cottontail rabbits. These animals are
prairie dogs. Some stand erect at the mouths of their burrows, view-

es*

"0° r . if 60° ; as° \ . se \

ie |

a |

——. ( uy, O

[isre® aoe -—.. se ‘ “oad }
dase ace Lass ‘ —— eer

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Fig. 24.—Distribution of plains prairie dog (Cynomys ludovicianus): The occupied area is marked with
dots.

ing the passing train; others are engaged in feeding or running to and
fro about the colony. The land they occupy is the broad expanse of
level and slightly rolling semidesert country known as the Great
Plains, a vast tract which stretches from the Rocky Mountains easterly
to the western edge of the Mississippi Valley, and from Montana and
North Dakota southward to Texas and Mexico. (See fig. 24.) The
plains are treeless, except along the streams, and the ground is sparsely
covered with grass and other small plants, which are green in early
spring and brown the greater part of the year.

“01

258 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

The prairie dog loves sunshine and a dry atmosphere, and in ranging
easterly from the arid plains toward the humid prairies of the Missis-
sippi Valley becomes less and less numerous, till between the ninety-
seventh and ninety-eighth meridians he disappears altogether. Not
even the luxurious vegetation of the prairies is sufficiently attractive
to lure him into the humid belt adjoining his chosen home. That he
is fond of rich vegetation and prefers it to the dry bunch grass of the
plains is shown by his great destructiveness to alfalfa, grain, and
other crops grown on irrigated lands within his range. This is an
important illustration of the law that in fixing the limits of distribu-
tion of animals climatic factors are even more potent than food.

The prairie dog is preeminently a social animal, living in colonies
which vary in extent from a few acres to thousands of square miles
and inhabited by thousands, and in some cases millions, of animals.
Colonies 20 to 30 miles in length are not rare, and in Texas one is
known which measures about 250 miles one way by 100 to 150 the
other, covering an area of about 25,000 square miles. The number of
holes in use on each acre varies from a few to upward of a hundred, and
probably averages at least 25. At Alma, Nebr., W. H. Osgood found
the number ranging from 35 to 64, and on an alfalfa field near Carls-
bad, N. Mex., Vernon Bailey found 1,009 on 20 acres, or 50 to the
acre. In old towns many holes are abandoned, or used only as refuges,
so that it is dificult to ascertain how many animals live in a stated —
number of holes. Another difficulty lies in the varying number of
animals in the occupied holes, for in winter and early spring the usual
number is two (a pair), while after the birth of the young the number
is at least quadrupled, and then decreases with the advance of the sea-
son, as the young are killed by enemies. It is certainly a conservative
estimate to assume the average number of animals per acre to be 25.
On this assumption, the number of prairie dogs in the great Texas
colony must be at least 400,000,000.

According to the formula for determining the relative quantities of
food consumed by animals of different sizes (kindly given me by Prof.
W. W. Cooke), 32 prairie dogs consume as much grass as 1 sheep, and
256 prairie dogs as much as 1 cow. On this basis the grass annually
eaten by these pests in the great Texas colony would support 1,562,500
head of cattle. Hence, it is no wonder that the annual loss from
prairie dogs is said to range from 50 to 75 per cent of the producing
capacity of the land and to aggregate millions of dollars.

GENERAL HABITS OF PRAIRIE DOGS.

When a person approaches a dog town the animals see him a long way
off and keep a close watch on his movements. As he comes nearer an
alarm note is sounded, at which those away from their burrows rush to
the entrance mounds, where they sit or stand erect, nervously twitching

Yearbook U. S. Dept. of Agriculture, 1901. PLATE XXil.

PHOTOGRAPHED BY C. HART MERRIAM.

HELIOTYPE CO., BOSTON.

THE PLAINS PRaiRiIE DoG (CYNOMYS LUDOVICIANUS).

THE PRAIRIE DOG OF THE GREAT PLAINS. 259

their tails and chattering or barking excitedly. If he continues to
move toward them the excitement increases, and most of the animals
on the near side of the colony plunge headlong into their burrows.
Some withdraw more slowly, and for some time their heads and eyes
may be seen peering up from the funnel-shaped openings of the mounds.
Those near by are usually silent, while those at a little distance con-
tinue to scold and chatter. This chattering or barking, as it is usually
called, can often be heard after the animals have gone down out of sight
in their holes. (Pl. XXII.)

Along railroads the animals have become so accustomed to tne trains
that they no longer take fright as the great noisy engine rushes madly
by, and they are best observed, perhaps, from the windows of passing
trains. Their indifference at such times is amazing. I have often
watched them from the ‘‘Overland Limited,” some standing erect
on their mounds; others chasing one another about or quietly feeding
within 40 or 50 feet of the roaring, rushing train, without showing
the least outward sign that anything unusual was happening. One
would think the fury and deafening roar would be too much for their
nerves, but they appear to regard it with absolute unconcern. It is
extraordinary how soon animals lose their fear of naturally terrifying
objects when such objects come and go frequently without doing them
bodily violence.

In summer, prairie dogs are most active mornings and evenings,
usually remaining in their holes during the hotter part of the day. In
fall they become very fat, and apparently sleep a good deal; at least,
they are much less regular and are less frequently seen. In winter,
in the southern part of their range, they may be seen nearly every day
unless itis stormy. Thus, in Texas and New Mexico they are said to
come out in good weather shortly after sunrise, even at times when
the teniperature is below freezing. On the northern plains they hiber-
nate irregularly, but still appear at intervals. The periods of hiberna-
tion are probably determined by storms and by the length of time the
ground is covered with snow, for in Montana and Wyoming they have
been known to appear, in places where the ground was bare, on calm
sunshiny days in midwinter when the mercury stood at or below zero.

Prairie dogs, like the desert species of kangaroo rats, pocket mice,
ground squirrels, and other rodents of arid regions, are able to live
and thrive without drinking. In many places the only moisture they
take into their systems is the small quantity contained in the dry
grasses, seeds, and roots they eat. In arid western Texas they are
abundant in places where the annual rainfall is slight and uncertain
and where some years pass without any rain. With respect to the
theory that their burrows are deep enough to reach water, it need
only be said that in some of the dog towns artesian wells have been
sunk to the depth of 1,000 feet without striking water.

260 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

TIME OF BIRTH AND NUMBER OF YOUNG.

The time of reproduction varies with the latitude and altitude, but
exact information as to the dates of birth and the number of young in
a litter in different parts of the plains is not at hand. In Texas the
young are usually seen at the mouths of the holes in early May, while
in North Dakota and Montana they rarely appear before the latter
part of May or first week of June. The usual number of young
seems to be four, but the cases in which the number is definitely
known are few.

MOUNDS AND BURROWS.

The mouth of each burrow opens in the middle of a mound, which
is usually a foot high and 3 or 4 feet in diameter (Pl. X XIII, fig. 1).
The mound increases in size with age, those that have been used for
many years attaining a height of 14 or 2 feet and a diameter of 8 or
10 feet. The interior of the mound is funnel-shaped, forming an
elevated crater-like rim around the entrance of the hole. This is
pressed into form by the nose of the animal, as may be seen in PI.
XXIII, fig. 3, which shows prints of the nose all around the inside.
After injury from rains or other causes the rim is repaired by serap-
ing up the ground from outside (Pl. XXIII, fig. 2). Sometimes the
repairs are made before rains, and some observers regard the animals
as exceptionally clever weather prophets. Thus, Maj. H. W. Merrill
states that whenever they are busy scraping the earth up around their
burrows and pressing it into place with their noses rain is sure to
follow in a very short time. The chief object of the elevated rim is
to keep the water out of the burrows when the ground is flooded by
sudden rains, as shown in Pl. XXIV, fig. 1. The ground immediately
surrounding each burrow is usually cleared of small plants and kept
clean and bare, and where burrows are near together the bare areas
often join, so that in thickly populated colonies the ground is hard
and smooth like a playground, and the animals are obliged to go some
distance for food. This they dislike to do, lest they be pounced upon
by enemies; hence, when the grass near their burrows has been con-
sumed they dig new holes nearer the supply. It takes a long time
tor vegetation to regain a foothold on the hard floors of the dog
towns, and the sites of old towns remain conspicuous for years after
they are abandoned.

The holes go down for some distance at a very steep angle and then
turn at nearly a right angle and continue horizontally, rising some-
what toward the end. The nests are in side chambers connecting
with the horizontal part of the burrow, and usually, if not always,
at a somewhat higher level (fig. 25, /7). Recently, at Alma, Nebr.,
W. H. Osgood dug out a burrow, of which he made a careful
diagram (fig. 25), accompanied by measurements. In this case the

Yearbook U. S. Dept. of Agriculture, 1901. PLATE XXIll.

PHOTOGRAPHED BY VERNON BAILEY. ELIOTYPE CO., BOSTON

FiG. 3.—INSIDE OF RIM OF MOUND, SHOWING NOSE MARKS,

MOUNDS OF THE PLAINS Prairie Doa.

vd

te

®

+8

Pe ee Se Se ee ee ee

THE PRAIRIE DOG OF THE GREAT PLAINS. 261

burrow went down nearly vertically to a depth of 144 feet below the
surface, when it turned abruptly and became horizontal, as shown in
the diagram. The horizontal part was 135 feet in length. One-
third of the horizontal part (the terminal 4 feet, 7”) and two old nests
and passageways (/”’) were plugged with black earth brought in from

B

A. Mound :
B. Funnel -shajred entranceto burrow F

C. a faye 42 inch.uvdvanreler
about I5 fect ue length

D. Horizontal [UASSAGED Ateetin length. :
E. unused neslsfilled with earlre retase.

F .2uused part of horizontalpassage
filedwrt earth etc (F# feel long)

G.Wichelarge enough for one praurte dog:

H. West of Grass (Minch uravemreter by Juv |:
ches iheght) °
J. Absorbent matter carrying bisuljrhidet
of carbo. - if
Posriton of Rratriedogs as found alter
ase of bisulrehide of car voiv

Leth of horizontal passage, /4 feet
Creches

Fig. 25.—Prairie-dog burrow.

the surface layer, which was very different from the light-colored
clayey earth in which the greater part of the burrow lay. Four or five
feet below the entrance was a diverticulum, or short side passage (().
probably used as a place in which to turn around when the animals
come back to take a look at the intruder before finally disappearing 1

262 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

the bottoms of their burrows. It is also used, apparently, as a resting
place where they bark and scold after retreating from the mouths of
the burrows. As elsewhere noted, they are often heard barking after
they have gone in. The burrow was opened the day after bisulphide
of carbon had been used for destroying the animals, and the material
carrying the bisulphide was found at the bottom of the vertical part,
just where the horizontal part turns off. Two dead animals were
found, one in the horizontal part, the other in the nest, as indicated
by the letter A’ in the diagram.

NATURAL ENEMIES.

The prairie dog has several mortal enemies which, when not inter-
fered with by man, usually serve to hold its numbers in check. The
most inveterate of these appear to be the coyote, badger, black-footed
ferret, and rattlesnake. Their methods of attack differ widely.

The coyote sneaks up to the borders of a colony, hiding behind
straggling tufts of vegetation and depending largely on his protective
coloration for concealment. He usually approaches when the animals
are in their burrows, and strives to reach some object behind which
he may hide and lie in wait until some unwary inhabitant comes out to
feed, when by a quick rush it may be headed off and caught.

The badger usually drives his prey into its burrow and then deliber-
ately digs it out. He is for his size one of the most powerful animals
in the world. His foreclaws are long and strong, and his sense of
smell is highly developed. On sniffing a prairie dog or gopher in its
burrow, he simply bores down to his victim, which has no possible
means of escape. .

The black-footed ferret is built like a weasel, and though much
larger, is small enough to enter and traverse freely the burrows of
prairie dogs, so that he is able to pursue them to the ends of their
holes and capture them with absolute certainty. He is, therefore, one
of their most relentless and terrible enemies, and if sufliciently abun-
dant would quickly exterminate all the inhabitants of the largest
colonies.

The rattlesnake, like the ferret, glides silently into the hole, but is
said to confine his attentions to the young, which he takes from the
nest or seizes in the passageways. Travelers on the plains, from the
time of Lewis and Clark to the present day, speak of finding young
prairie dogs in the stomachs of rattlers killed in the dog towns. The
usual number so found appears to be one or two, but Dr. J. A. Allen
states that he once found three. One author claims that in Texas
these reptiles live almost wholly on the young of the prairie dog and
do more, perhaps, to keep down the numbers than all other agencies.
This writer continues:

A curious thing about the snake and the dog is that each 1s mortally afraid of the
other. The dog is afraid of being eaten by the snake, and the snake is afraid of

THE PRAIRIE DOG OF THE GREAT PLAINS. 2638

being entombed by the dog. If the mother of the young dogs, on a return to the
home hole, finds that a snake has intruded, she at once sets up a peculiar ery or bark,
to which all the citizens of the town at once respond. They gather about the hole,
and in a moment all are at work filling it up. The quickness with which they can
do this is remarkable. When the hole is filled they butt and pack the dirt in the
mouth of the hole till it is almost as hard as the prairie adjacent. There is no chance
for an escape of the invader. He is sealed up in his tomb. The snake understands
this danger, and is prepared to escape from it on the least warning. A handful of
dirt thrown in a hole where the snake is will bring him.with all speed out of the
hole, because he is under the impression that the dogs are about to seal him up.!

There are other enemies also, such as cougars or mountain lions,
bobeats, eagles, hawks, and owls, but most of them are not sufficiently
abundant on the Great Plains to be regarded as important factors in
holding the prairie dog in check. Still, in some localities, hawks and
owls kill large numbers of the young. They should be protected and
encouraged.

RECENT INCREASE AND SPREAD OF PRAIRIE DOGS.

Formerly the area of available land in proportion to the population
was so great that little attention was paid to such pests as prairie dogs
and gophers. But in recent years the development of improved
methods of farming, including irrigation and artesian water supply,
has led ranchmen to push farther and farther westward over the semi-
arid plains, until agriculture and stock raising have invaded most parts
of the prairie dog’s domain, the land holdings have decreased in size
and increased in value, and the depredations of pests are more keenly
felt.

On many parts of the plains prairie dogs are now more abundant
than formerly and their colonies have overspread extensive areas pre-
viously unoccupied. This is due to the coming of the white man,
whose presence favors their multiplication in two ways—(1) by increas-
ing the food supply, and (2) by decreasing the animal’s natural ene-
mies. The white man cultivates the soil and thus enables it to support
a larger number of animals than formerly; at the same time he wages
warfare against the coyotes, badgers, hawks, owls, snakes, and other
predatory animals which had previously held the prairie dogs in check.
Thus favored, the prairie dogs have multiplied until they have become
one of the most pernicious enemies to agriculture. The increase of
late years is well known to ranchmen on the plains, but for the intor-
mation of others a few definite instances recently collected by my
assistants may be of interest.

Richard Harrison, of Blunt, S. Dak., states that ten years ago there
were possibly 25 occupied burrows on his land; the animals increased
slowly and six years ago not more than 10 acres were infested. Since
then the increase has been so rapid that at present the area they occupy
covers about 160 acres.

264 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

O. E. McArthur, also of Blunt, S. Dak., states that about fifteen years
ago his children noticed two or three burrows about a mile from his
house, and that no particular attention was paid to the inmates, which,
during the next few years, increased slowly. A little later, however,
they spread over so much land that their multiplication became a mat-

ter for serious alarm. At present they occupy a full quarter section

(160 acres), having surrounded Mr. McArthur’s house and taken pos-
session of all the land near it. }

A cattle ranch in Logan County, Kans., which ten years ago pas-
tured a thousand head -of cattle, will barely support 500 at present,
owing to the great increase in prairie dogs, which have overrun the
range. Practically, the whole of the southern half of Logan County
is now one continuous dog town, estimated to cover about 300 square
miles. In the past decade the population of this area has decreased, a
post-office (Elkader) has been abolished, and many homes have been
vacated, the result, it is said, of the great increase in prairie dogs.

At Carlsbad, in the Pecos Valley, New Mexico, in September, 1901,
Vernon Bailey studied a colony of prairie dogs which completely cov-
ered a 20-acre alfalfa field, 4+ or 5 acres in each of two adjoining fields,
and several acres of prairie. He was told that this large colony had
spread in three years from a small one in a corner of the alfalfa field.

E. W. Nelson states that when he and his brother located ranches
in a mountain valley in eastern Arizona in 1884, the only prairie dogs
in the vicinity were a colony 3 miles distant, inaccessible except by
way of a narrow box canyon. About three years later a prairie dog’s
burrow was found on the ranch, after which the animals multiplied
steadily, until in 1895 they occupied a large part of the valley.

Complaints are constantly received of the spread of the pests on farm
lands adjoining Government, railroad, school, and other lands, over
which the inhabitants have no jurisdiction. This is a very serious
evil, and one with which it is exceedingly difficult to cope.

FOOD.
The normal food of the prairie dog is grass, chiefly the bunch grass

of the plains... In addition to this, grass roots, other plants, seeds, and
sometimes insects are eaten.

DESTRUCTIVENESS.

The damage done by prairie dogs consists in the loss of grass and
other crops eaten, or buried under the mounds; in the accidental
drainage of irrigation ditches,’ and in the danger to stock from stum-

‘In Stillwater Valley, Montana, an irrigating ditch on a side hill was tapped by a
prairie dog burrow and the water came out 50 feet lower down on the slope. The
hole was twice stopped and the ditch moved a little, but the break recurred, and it
was finally necessary to dig a new ditch around the washout.

Yearbook U. S. Dept. of Agriculture, 1901.

PHOTOGRAPHED BY V. BAILEY AND W. H. OSGOOD.

Fic. 3.—NEW MOUND IN ALFALFA FIELD.

MOUNDS OF THE PLAINS PRrairi€ Dos.

PLATE XXIV.

ery ee eee eee ete

THE PRAIRIE DOG OF THE GREAT PLAINS. 965

bling in the holes. Running horses often trip and break their legs,
and riders are sometimes injured and even killed.

On ranch lands prairie dogs have proved destructive to a variety of
crops, among which are alfalfa (Pl. XXIV, figs. 2 and 3), grain, pota-
toes, and sugar beets, and on grazing lands they are said to consume,
or bury under their mounds, so much grass that the capacity of the
land for supporting stock is reduced, as already noted, from 50 to 75
per cent. A prominent Texas newspaper recently published an edito-
rial containing the following:

No man who has not gone through the portions of Texas infested by prairie dogs
can conceive the enormous ravages they have committed. Millions of acres of land
once covered with nutritious grasses have been eaten off by these animals, until the
land is naked and worthless, and will remain worthless so long as the prairie dog
remains. They invade the farms and eat down the growing crops. Here and there

individual effort has been made to destroy them, without avail, and their numbers
steadily increase, until they are a menace to the prosperity of the land.

POPULAR INTEREST IN THE DESTRUCTION OF PRAIRIE DOGS.

The general apathy of a few years ago, when land was plentiful and
of little value, has given place to widespread and active effort to rid
the country of the pests. Wherever our field experiments have been
made, from the Dakotas to Texas, the inhabitants were found fully
awake as to the necessity for immediate action, and hundreds, if not
thousands, of them had already expended time and money in single-
handed efforts. The recent attempt of the National Government to
ascertain the simplest and most efficient means of combating the evil
has been received with universal approval. With one or two excep-
tions, our field men were granted free access to private lands, and in
most instances were enthusiastically received and accorded every assist-
ance and courtesy. In some cases, where the animals are rapidly
increasing, the actual and prospective losses are so great that ranch-
men expressed their willingness to pay for the destruction of the ani-
mals at a rate per acre exceeding-the actual market value of the land.

METHODS OF DESTRUCTION.

In the case of prairie dogs, as in the case of gophers and ground
squirrels, numerous remedies have been suggested and tried, most
of which have met with a certain measure of success. Few, how-
ever, have proved available on a large scale. It is easy to destroy
isolated animals, and to completely exterminate the inhabitants of
small isolated colonies, but, as a rule, the problem confronting the
sufferer from prairie dogs is one of larger dimensions; to cope with
it successfully means the employment of measures and remedies that
are simple, easily handled, available on a large seale, and last, but
not least, not too costly (either for materials or labor) to be used
over areas comprising thousands of acres. The cost on large ranches

266 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

should not exceed 18 cents per acre, and should fall as far short of
this, as possible.

Among the measures that succeed well enough on a small scale or
under special conditions are trapping, drowning, destruction by
domesticated ferrets, and capture in sand barrels and straw barrels
placed over the holes. On a large scale, poisoning and fumigating
have yielded the best results.

POISONING.

By poisoning is meant the administration of a poison or combination
of poisons by means of some article of food which the animals will
readily eat. The poisons most in favor are strychnine and cyanide of
potassium. Phosphorus also has been used and is an ingredient of
many of the poison mixtures sold in the stores. It is efficient, but its
use is attended with danger, and it is not recommended by this Depart-
ment. .

CYANIDE OF PoTASSIUM.—Cyanide of potassium kills quickly, and is
an excellent poison, but it is sometimes difficult to administer, chiefly
on account of its odor, which is offensive to most animals. Like
phosphorus, it is dangerous to man, and must be handled with great
eare. It is said to lose its power when wet or exposed to the atmos-
phere. It has been administered in prunes and raisins, and (in combi-
nation with strychnine) is a component of the celebrated Peters mix-
ture for poisoning grain, in which it is disguised by a coating of
molasses, flavored with oil of anise.

STRYCHNINE.—Strychnine is probably, all things considered, the
best and most satisfactory poison now known for the destruction of
prairie dogs. It can be obtained everywhere, usually at a moderate
price, and its use is simple. The minimum dose necessary to kill
prairie dogs is not known, but it is safe to say that the quantity recom-
mended in the Peters formula (8 ounces to a bushel of wheat) is exces-
sive. Two ounces is doubtless sufficient, and 14 ounces is probably
enough. (For ground squirrels, 1 ounce to the bushel of grain is
ample.) The strychnine sulphate should be dissolved in warm water,
in which the grain should be soaked for twenty-four or thirty-six
hours, until all is absorbed. Some experimenters find this suflicient;
others prefer to sweeten the grain by stirring in a quart or two of
molasses and sprinkling with enough corn meal to prevent sticking.
Some use corn meal alone, made into pellets, without any whole grain,
Another way to administer strychnine is to introduce small quantities
in prunes or raisins, in pieces of apple, carrot, or turnip, or on bread
and butter. In the last case it is said that the strychnine should be
sprinkled on buttered bread and then coated lightly with sirup, after
which the bread is cut in small squares and placed around the burrows.
The cost of strychnine sulphate, as customarily sold in small Western

THE PRAIRIE DOG OF THE GREAT PLAINS. 267

towns, is $1.50 to S2 per ounce. It comes in 1-dram (4-ounce) bottles
which usually retail for 25 cents. Assuming that 2 ounces is the
quantity necessary to poison a bushel of grain, the poisoned grain
would cost about $5 per bushel. Allowing a tablespoonful to be the
average quantity necessary to scatter about each hole, and allowing 50
holes to the acre,' a bushel of grain will poison 40 acres, at a cost of
123 cents per acre. A man can scatter poisoned grain over 50 acres
or more per day; hence, if labor costs $1 per day, the expense per
acre of putting out the poison would be 2 cents, which added to the
above 123 cents for materials, makes the total cost 145 cents per acre.
The first application of the poison, if carefully made in late winter or
early spring when food is scarce, may be counted on to kill 75 to 80
per cent of the animals (and has been known to kill as high as 95 per
cent), and this at a cost per acre of less than 15 cents. The second
application, a week or two later, is aimed at the few remaining occu-
pied holes, which should not average more than two or three to the
acre, and the cost per acre should not exceed 1, or at most, 2 cents.
If any animals remain, they may be killed by bisulphide of carbon,
and in many cases it is better to do away with the second poisoning and
use bisulphide to kill off those that are left after the first poisoning.

FUMIGATION.

By fumigation is meant the destruction of animals by fumes arising
from substances thrown into the burrows, as bisulphide of carbon, or
generated outside and forced in by mechanical appliances known as
‘‘fumigators.” Fumigators are devices by means of which fumes from
burning sulphur or other materials are pumped into the burrows. In
parts of the West, particularly California, they have been used with
success in killing gophers and ground squirrels. They have been suc-
cessfully used also against prairie dogs, but their employment for this
purpose does not appear to be gaining ground.

BISULPHIDE OF CARBON.—Bisulphide of carbon is a volatile liquid
which rapidly loses its strength on exposure to the air, and should be
kept in tightly corked bottles or cans, which, when used, should be
immediately recorked. It is inflammable and highly explosive, and
should never be opened in the vicinity of a light or fire. Its fumes
are heavier than atmospheric air, and when introduced into burrows
sink quickly to the bottom.

The method of application is exceedingly simple. The usual dose
for prairie dogs is 1 ounce (about a tablespoonful). This quantity
should be poured on some absorbent substance, such as a lump of horse
manure, a corncob, a handful of rags, or even a clod of earth, which

‘A large average, but made to include unoccupied holes, as it is much cheaper to
put out a little extra grain than to plug the holes to find out which are occupied.
Furthermore, grain scattered anywhere in the dog towns is liable to be eaten.

268 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

should be immediately dropped into the burrow, the mouth of which
should then be closed.

For introducing the bisulphide there is nothing better than dry
horse manure—a material which costs nothing and is always at hand.
A lump of horse manure wet with the bisulphide and dropped into a
hole falls at once to the bottom of the vertical part, as shown in the
diagram (fig. 25, /), where it is very near the animals. The liquid
can be used to best advantage after a rain, when the interspaces in the
soil are filled with water, so that the fumes are less readily diffused
into the surrounding ground. This, however, is of much Jess conse-
quence in the case of prairie dogs, which are deep-burrowing animals,
than in the case of pocket gophers and ground squirrels, whose bur-
rows and tunnels, as a rule, lie much nearer the surface.

Crude bisulphide, suitable for killing prairie dogs and other bur-
rowing animals, costs about 10 cents per pound in 50-pound carboys
or drums. A dollar’s worth is enough to poison 100 holes. The cost,
therefore, is about 1 cent a hole. The fluid should not be introduced
haphazard into the burrows of a colony, but should be used only in
those which the animals have been seen to enter immediately before it
is applied. In this way none is wasted on unoccupied holes.

GENERAL DIRECTIONS FOR PRAIRIE-DOG DESTRUCTION.

Poisons are of very little use except in winter and early spring,
when the ordinary food of the prairie dog is scarce and difficult to
obtain. At such times poisoned grain, vegetables, fruit, and bread
and butter are freely eaten. In distributing the poisoned grain or
other material, it is usually better to scatter it about the holes instead
of putting it into the mouths of the burrows, where it gets mixed
with the dirt and is trodden down by the animals and lost. An excep-
tion to this course is recommended in case of the use of pellets of grain,
made by wrapping teaspoonful doses of poisoned grain in greasy tissue
paper; these should be dropped into the burrows. The danger to stock
is much less when the grain is scattered about the colony than when
it is placed in spoonfuls at or near the openings of the burrows. In
vase any considerable number of animals are left after the first poison-
ing the ground should be gone over a second time.

It should be clearly understood that the method recommended by
this Department consists in two steps, the first of which is to destroy
the great bulk of the inhabitants of a colony by poisoning with
strychnine, applied in winter or early spring when food is scarce; the
second, to kill the remaining animals with bisulphide of carbon. In
this way it is believed that colonies of any size may be wiped out ata
total cost not to exceed 16 or 17 cents per acre, probably less.

Bisulphide is probably the most efficient single agent known for
the destruction of prairie dogs, and can be used, of course, for the

THE PRAIRIE DOG OF THE GREAT PLAINS. 269

extermination of colonies of any size, and at any time of year when
the animals are active. If the killing is put off until late spring or
early summer, when food is plenty, the animals are not likely to eat
enough of the poisoned grain to amount to anything, and bisulphide
becomes the best remedy. The only objection to its general use is its
cost, which is likely to be about 1 cent per hole.

OBSTACLES AND DIFFICULTIES OF EXTERMINATION.

The chief obstacle to the extermination of prairie dogs on the plains
is lack of cooperation among landowners. It is of little use to kill
off the animals on ranches adjacent to large colonies in which the pests
are allowed to go on multiplying. Many ranchmen who have again
and again poisoned those on their own lands have finally given up in
despair because of the rapid overflow from adjoining lands, new ani-
mals continually taking the places of those killed, until the expense
and labor of repeated poisonings were too great to be continued. Com-
»laints from this source are common in the case of ranches adjoining

tovernment, State, or school lands, and railroad lands, and occasionally

arise in the case of those adjoining lands owned by nonresidents, cor-
porations, and certain individuals. This phase of the subject requires
local legislation. In some States drastic measures have been recom-
mended. Thus, in Texas, during the session of 1899, a bill was intro-
duced making it the duty of every man owning land inhabited by
prairie dogs to destroy the animals, under penalty of a fine not exceed-
ing $100 for each section or part of a section on which the pests were
allowedto remain. In the case of land owned by corporations or non-
residents, the destruction of the animals was provided for, the expense
to be a lien on the land. While this bill failed to become a law, it had
many supporters, and goes far to show the real extent of the prairie-
dog scourge.

The Kansas legislature has recently appropriated $5,000, to be
expended under the supervision of the regents of the State agricul-
tural college, in ‘* experiments for the purpose of determining the
most effective and economical method of destroying prairie dogs and
gophers,” and has also authorized the township auditing boards to
expend $100 [or more if requested by two-thirds of the electors of
such township] in each township each year for the destruction of these
animals (approved February 12, 1901).

PRAIRIE DOGS ON NANTUCKET.

In 1890-1892, one or two pairs of prairie dogs were introduced into
Nantucket, where, for several years, they increased slowly and were
regarded with interest. After a few years, however, they grew so
numerous and spread so rapidly that the inhabitants became greatly

270 YEARBOOK OF THE DEPARTMENT OF AGRICULTURE.

alarmed and feared the animals would overrun the whole island. Mr.
Outram Bangs wrote in December, 1899, that when on a visit to the
island during the summer and fall of the same year he counted 200
prairie dogs visible at one time in one colony, and states that three or
four such colonies existed, besides many scattering pairs and small
colonies. A specimen sent the Biological Survey by Mr. Bangs proves
to be the plains species (C'ynomys ludovicianus), in rather red pelage,
and probably came from some point on the Great Plains between
western Kansas and Texas. ,

W. W. Neifert, writing from Nantucket, under date of February 12,
1900, states that ten years previously two pairs of prairie dogs were
brought to the island, where they multiplied so rapidly *‘that they are
now counted by thousands, and are a dangerous pest and nuisance,
destroying crops and fields;” also, that ‘‘at a recent town meeting a
committee was appointed with a view of exterminating them and an
appropriation of $350 was made to procure poison.” In a subsequent
letter, Mr. Neifert writes: ‘‘In addition to the $350 raised by the
town, about $200 was subscribed by farmers and others interested.
The poisoning scheme was adopted, and bisulphide of carbon was the
drug. A bunch of old rags was saturated and placed in the mouth of
the burrow and the hole closed with dirt or sod. This method was
simple and inexpensive but did the work successfully, and now there
is not a dog left to tell the tale.”

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