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UNITED STATES DEPARTMENT OF AGRICULTURE

MISCELLANEOUS PUBLICATION No. 115



Washington, D. C.



April, 1931



INFORMATION FOR THE GUIDANCE OF FIELD MEN AND COOPERATORS OF THE BUREAU
OF BIOLOGICAL SURVEY ENGAGED IN THE CONTROL OF INJURIOUS RODENTS AND
PREDATORY ANIMALS

Prepared under the direction of Paul G. Redington, _Chief,
Bureau of Biological Survey_, in the Division of Predatory-Animal and
Rodent-Control, Stanley P. Young, _Principal Biologist, in
Charge_



CONTENTS


                                                               Page

  Introduction                                                    1
    Necessity for control of wild-animal pests.                   1
    Control functions of the Bureau of Biological Survey          2
    Legal authorization for control work                          2
    Instructions previously issued                                3

  Animals on the control program                                  3
    The injurious rodents                                         3
    The predatory animals                                         3
    Other forms subject to control                                4

  Instructions regarding field practices                          4
    The objective                                                 4
    Conservation, State laws, and cooperation                     4
    Precautions in handling poisons                               4
    Rodent-control operations                                     6
    Predatory-animal control                                      6




INTRODUCTION


NECESSITY FOR CONTROL OF WILD-ANIMAL PESTS

The demands made upon the Federal Government some years ago for aid in
suppressing those wild animals of the public domain that continually
spread out into areas that had been placed under cultivation or used
for grazing purposes produced the first Federal cooperative efforts
toward the control of predatory animals and injurious rodents. The
settler who saw the profits of his early work wiped out by the
incursions of wolves, coyotes, mountain lions, and bobcats from the
public domain into his stock ranges, and of prairie dogs, ground
squirrels, pocket gophers, jack rabbits, and other rodents into his
cultivated fields, had no recourse other than to ask the aid of the
Government whose lands served as breeding reservoirs from which these
predators and rodents came. Otherwise they would reinfest his stocked
and cultivated acres in spite of all that he could do to prevent them,
either single handed or with the aid of his neighbors.


CONTROL FUNCTIONS OF THE BUREAU OF BIOLOGICAL SURVEY

The administration of wild life by the Bureau of Biological Survey
involves not only research into the habits, distribution, and
requirements of the varieties, and the conservation of fur, game,
insectivorous, and other valuable animals, but also the regulation
of activities of a limited number of certain species that seriously
interfere with the economic interests of man, and, in the case of some
of the larger predators, prey upon valuable game species.

The leadership of the Biological Survey in control operations during
the years since 1915 has been requested and encouraged by State and
other cooperating agencies. The funds made available from these sources
for expenditure under the direction of the district leaders of the
bureau have been far in excess of those provided for the purpose from
the National Treasury. The investigations of the food and other habits,
the geographic distribution, and the relationships of the wild birds
and mammals of the country (including rodents and predators) have been
carried on for almost half a century and provide the basis for the
control work recommended and prosecuted. Research along these lines is
being continued by scientifically trained men and will be expanded as
funds permit.

It is well for the conservation of the wild life of the country that
leadership in the control of injurious species has been delegated to
a governmental organization that is concerned with the welfare of the
various forms and with the administration of wild-life refuges, one
that is charged with the enforcement of wild-life conservation laws,
and one that recognizes the desirability of preserving representatives
of all forms of wild life on suitable areas.

LEGAL AUTHORIZATION FOR CONTROL WORK

The legal sanction for control work by the Federal Government is
contained in congressional direction in annual appropriation acts for
the Department of Agriculture and in a special enactment authorizing a
definite control program. The appropriation acts making funds available
for the use of the Bureau of Biological Survey since the year 1915
have provided for investigations, experiments, demonstrations, and
cooperation for the control of wild animals injurious to agriculture,
horticulture, forestry, animal husbandry, and wild game, and for the
suppression of rabies in predatory wild animals. The special program
of control, which was called for by the Seventieth Congress, was drawn
up by the Department of Agriculture to cover a 10-year period, and was
approved by the Seventy-first Congress (Public Act No. 776, of March 2,
1931).


INSTRUCTIONS PREVIOUSLY ISSUED

Information regarding new developments and improved practices in
control procedure has been made available to the field personnel and
to cooperators of the bureau from time to time since the inception
of the cooperative work in 1915, in mimeographed and printed form,
as well as by individual written instructions and personal contact.
It is now desirable to compile the more important of the statements
as to policy and specific directions in one publication. All control
methods are based on fundamental research and give due consideration
to safeguarding the useful and harmless forms of wild life and the
public interests in general. Field methods have been adapted to meet
varying local conditions as called for by research and the experience
of field forces. Investigations and experiments are being continued,
and as additional information becomes available, field practices will
be subject to such modifications and improvements as the conditions
warrant.




ANIMALS ON THE CONTROL PROGRAM


THE INJURIOUS RODENTS

Certain species of the rodents that in large numbers infest lands of
value for crop or forage production must be eradicated locally to
meet the requirements of agriculture and forestry. Those that figure
most largely in the cooperative control operations in one part or
another of their ranges are the prairie dogs, ground squirrels, pocket
gophers, jack rabbits, porcupines, and native and introduced rats and
mice. Other groups that locally become unduly numerous and destructive
may also on occasion come within the control program. It would be
impossible to eradicate everywhere the ground squirrels, prairie dogs,
and other rodents that range over vast areas of relatively worthless
lands, and such action is not desirable, even on the public domain. In
areas of economic importance, however, definite tracts are established
where the rodents can be kept under thorough control, and operations
are extended sufficiently to prevent reinfestation.


THE PREDATORY ANIMALS

The control of such predatory wild animals as coyotes, wolves, mountain
lions, and bobcats is concentrated on areas where serious damage is
being done to domestic stock, poultry, and game. Bears are not subject
to control except when individually injurious to livestock or property.


OTHER FORMS SUBJECT TO CONTROL

Though the chief control work directed by the Biological Survey is
concerned with injurious rodents and predatory mammals, it sometimes
becomes necessary to investigate cases of damage by other classes
of animal life, including moles, crawfishes, and land crabs, and to
recommend measures for their control.




INSTRUCTIONS REGARDING FIELD PRACTICES


THE OBJECTIVE

The underlying policy of the Biological Survey with regard to injurious
species of wild animals has been and will continue to be one of control
rather than complete eradication. The bureau is not embarked upon a
general extermination program, but with every proper consideration
for conservation interests, it has as its objective in this field the
adequate local control of injurious mammals, so that the burdensome
losses suffered by farmers and stock raisers may be reduced to the
minimum and beneficial forms of wild life protected from undue
destruction by their natural enemies. Though in some cases this may
mean local eradication of harmful forms, it will not result in the
general extermination of any species.


CONSERVATION, STATE LAWS, AND COOPERATION

The Bureau of Biological Survey is an organization primarily and
vitally interested in the conservation and protection of all forms of
wild life, particularly where they are more beneficial than harmful.
Those engaged under its direction in the control of predatory animals
and injurious rodents are instructed to cooperate closely with Federal,
State, and local officials intrusted with the administration of
wild-life protective laws. They must also observe State and local laws
regarding the protection of life and property, the exposing of poisons,
and the trapping or otherwise endangering of valuable species. Control
operations on State and private lands must be conducted in close
cooperation with State officials and with property owners and tenants.


PRECAUTIONS IN HANDLING POISONS

Since poison may be dangerous in the hands of inexperienced and
incompetent persons, every possible precaution must be taken when it is
used in control operations, to safeguard persons, domestic stock, and
harmless and beneficial wild life.

Poisons should not be exposed on private lands without the consent of
the owners.

Control workers should familiarize themselves with appropriate
antidotes for poisons used and be in a position to administer them
promptly should the necessity arise.


RODENT-CONTROL OPERATIONS

Extreme care should be exercised in handling poisons in rodent-control
work. Prepared poisons should be placed in strong, properly labeled
containers and should be distributed only to assistants working under
the direct supervision of bureau leaders or to responsible cooperators.

Strychnine (in the alkaloid form) is the poison most largely used in
rodent-control, its speedy action making it one of the most humane.
Moreover, numerous tests have shown that in the quantities employed
in control operations strychnine is relatively harmless to such
gallinaceous birds as quail, pheasants, grouse, and domestic chickens.
The smaller birds also are safeguarded because of the fact that the
grains used in poisoned baits are of the large-kerneled kinds, such
as oats, and contain a minimum of weed seeds and cracked kernels.
Furthermore, in a large portion of the baits used the kernels are
steamed, rolled, and flattened so that their increased size lessens
their attractiveness to the smaller birds.

The use of red squill in the control of house rats and mice is
recommended, as it is an effective and specific poison for these
rodents and relatively harmless to other forms of animal life.

The use of thallium in rodent-control will in some places succeed where
strychnine alone fails. It should not be used, however, except to a
very limited extent in follow-up operations against ground squirrels,
prairie dogs, and rats. Such limited use of thallium should be guarded
with the greatest care under close and fully competent supervision,
as it is extremely dangerous to all life. Though thallium is highly
effective in destroying rodents, it can not be overemphasized that this
poison is not to be recommended for general use, except to supplement
strychnine in follow-up work. It should never be handled without
careful consideration in each particular case of all the potential
dangers involved.

Arsenic, cyanides, and phosphorus should not be used or recommended
for rodent-control, as they are not now known to have any special
advantages, and furthermore they may be a menace to other forms of
animal life. Not only is phosphorus dangerous to beneficial wild life,
but it is particularly unsafe because it sometimes causes fire.

Poisonous gases, which are efficient in the fumigation of burrows,
grain bins, and garbage dumps, should be used only by trained and
experienced workers in rodent-control.


PREDATORY-ANIMAL CONTROL

Poisoning operations for the control of predatory animals should be
limited strictly to areas where there is urgent need. They will not
be undertaken under the direction of the Biological Survey where
trapping or other means of control are practicable and the cost is not
prohibitive.

The handling of poisons should be intrusted only to properly trained
men working under the supervision of the Bureau of Biological Survey.

Poison stations set for coyotes and wolves should be placed away from
the timbered and well-watered areas that are frequented by foxes,
raccoons, skunks, minks, and other valuable forms of carnivorous
animals.

In many agricultural sections poisons should not be used at all because
of the obvious risks.

The methods of handling poisons developed and used by the Biological
Survey can be employed most effectively and economically in controlling
predatory animals at proper seasons in regions where conditions are
favorable. Poison is especially suitable for winter use against
predators on some of the great stock ranges of the West, as it can then
be employed with little or no danger to useful life. The cost of the
same measure of control by any other known means would be practically
prohibitive.

The control of predatory animals is an exceedingly difficult and
costly task, and the use of poisons in this work, particularly under
experienced supervision, materially reduces the expense. When properly
used, poison should not be more destructive to other species than the
use of traps, and in some cases it has been found to be even less
harmful and more humane.

Hunters should take every precaution to protect harmless and valuable
mammals and birds and should be familiar with the antidotes for each
poison used.

Only strychnine as processed by the Biological Survey should be used
in operations against predatory mammals, because it can be handled
safely, is constant in effect, and, since it kills quickly, its action
is humane.

Baits made of small pieces of perishable fat should be used almost to
the exclusion of others by field men and cooperators of the bureau.
They should be systematically placed about "decoy stations" consisting
of carcasses of worn-out horses or other useless animals or pieces of
meat. Wherever possible they should be placed in slight depressions and
covered with thin flat stones, pieces of hide, or other light material,
as coyotes and wolves can easily detect them under such cover, but they
are thus made inaccessible to birds.

Stations where poison is placed should be posted to warn owners of
stock or valuable dogs of the danger. Conspicuous warning signs such as
those furnished by the Bureau of Biological Survey in its cooperative
work should be used for the purpose.

In dispensing poisons for the use of cooperators in predatory-animal
control, Biological Survey field leaders are instructed to exercise the
greatest care to make sure of the integrity, honesty, and cooperative
spirit of those requesting supplies. When the leader has satisfied
himself as to the intent of the cooperator, he should keep in close
touch with him and observe his methods, to make sure that the poison
is being properly used and that no supplies are left in his possession
after cooperative work has been terminated.

Studded stations, or those in which the poison is placed in parts of
the carcass instead of about it, are to be used only under especially
favorable conditions. Their use is sometimes justified along the known
runways of predatory animals on high barren mountain ridges, high
benches, or stock driveways that can not be visited by the hunter after
the first heavy snowfall. Such stations should be at some distance from
timber, to make remote the danger of poisoning fur bearers. As soon
as trails are open in spring, the hunter is directed to revisit such
stations and bury or burn all the baits.

All predatory-animal hunters must visit their poison stations as
frequently as possible, and except under extraordinary conditions
should avoid making long poison lines. Baits that have become rancid
should be destroyed, and on completion of the poisoning work a general
clean-up must be made, and all baits possible destroyed. The use of
perishable fat baits is particularly recommended for the reason that
they are readily disposed of naturally, for those that can not be
located usually disintegrate in warm weather and become harmless after
they have melted and soaked into the ground.

Bears are ordinarily classed as game animals and are protected as
such. Only when they are doing material damage should they be taken,
and then by traps or by aid of dogs, and not by poison. State laws on
the subject must be observed. Field men and cooperators must exercise
the greatest possible care to kill only those individuals responsible
for damage, and must remove no more bears from a locality than it
is absolutely necessary to take in order to stop the destruction of
livestock.

In placing traps for the capture of injurious wild animals every
possible precaution is to be taken to avoid the accidental capture of
valuable game and fur-bearing animals and other harmless or beneficial
forms of wild life. Hunters working under the supervision of the
Biological Survey are instructed to visit their trap lines
as frequently as possible and to liberate game animals and
foxes, badgers, skunks, martens, minks, raccoons, and other animals
accidentally caught, unless they are so injured that they can not
survive. In occasional individual cases, however, where fur bearers do
serious injury to livestock or poultry, it is permissible to trap and
kill them if in accordance with State laws.

The most nearly humane traps available should be used, and trap lines
should be so placed that they can be visited at frequent intervals, to
avoid any unnecessary suffering, injury, or loss of trapped animals.



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