Title: Methods of Destroying Rats - Farmers' Bulletin 297
Author: Lantz, David
Language: English
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Issued May 31, 1907.

U. S. DEPARTMENT OF AGRICULTURE.

FARMERS' BULLETIN 297.

METHODS OF DESTROYING RATS.

BY

DAVID E. LANTZ,

_Assistant, Bureau of Biological Survey_.

[Illustration]

WASHINGTON:
GOVERNMENT PRINTING OFFICE.
1907.

[Transcriber's Note: Words surrounded by tildes, like ~this~ signifies
words in bold. Words surrounded by underscores, like _this_, signifies
words in italics.]



LETTER OF TRANSMITTAL.


U. S. DEPARTMENT OF AGRICULTURE,
BUREAU OF BIOLOGICAL SURVEY,
_Washington, D. C., May 15, 1901_.

SIR: I have the honor to transmit herewith for publication Farmers'
Bulletin No. 297, containing concise directions for the destruction of
damage done by these rodents, both in cities and in the country, is
enormous, and the calls for practical methods of destroying them are
correspondingly numerous and urgent. It is believed that by following
the directions here given the numbers of this pest can be greatly
reduced and the losses from them proportionally diminished.

Respectfully,

C. HART MERRIAM,
_Chief, Biological Survey_.

HON. JAMES WILSON,
_Secretary of Agriculture_.



CONTENTS.
                               Page.

Introduction                      3

Methods of destroying rats        4

  Poisoning                       4
  Trapping                        5
  Use of ferrets and dogs         6
  Fumigation                      7

Rat-proof construction            7

Natural enemies of rats           8

Conclusions                       8



ILLUSTRATION.
                                            Page.

FIG. 1.--Method of baiting guillotine trap      6



METHODS OF DESTROYING RATS.


INTRODUCTION.

The brown or Norway rat (_Mus norvegicus_) is the worst mammal pest in
the United States, the losses from its depredations amounting to many
millions of dollars yearly--to more, indeed, than the losses from all
other injurious mammals combined.[A] In addition to its destructive
habits, this rat is now known to be an active agent in disseminating
infectious diseases, a fact which renders measures for its destruction
doubly important.

[Footnote A: Several species of rats are known as "house rats,"
including the black rat (_Mus rattus_), the roof rat (_Mus
alexandrinus_), and the brown rat (_Mus norvegicus_). Of these, the last
is the commonest and most widespread in this country. Not one of these
species is a native, but all were imported from the Old World. As their
habits in general are similar, the instructions given in the bulletin
apply alike to all.]

Introduced into America about the year 1775, the brown rat has
supplanted and nearly exterminated its less robust relative, the black
rat, and despite the incessant warfare of man has extended its range and
steadily increased in numbers. Its dominance is due to its great
fecundity and its ability to adapt itself to all sorts of conditions. It
breeds three or four times a year and produces from 6 to 12, and even
more, young at a litter. Young females breed when only 4 or 5 months
old. The species is practically omnivorous, feeding upon all kinds of
animal and vegetable matter. It makes its home in the open field, the
hedge row, and the river bank, as well as in stone walls, piers, and all
kinds of buildings. It destroys grains when newly planted, while
growing, and in the shock, stack, mow, crib, granary, mill, elevator, or
ship's hold, and also in the bin and feed trough. It invades store and
warehouse and destroys fur, laces, silks, carpets, leather goods, and
groceries. It attacks fruits, vegetables, and meats in the markets, and
destroys by pollution ten times as much as it actually eats. It carries
disease germs from house to house and bubonic plague from city to city.
It causes disastrous conflagrations; floods houses by gnawing lead water
pipes; ruins artificial ponds and embankments by burrowing; destroys
the farmers' pigs, eggs, and young poultry; eats the eggs and young of
song and game birds; and damages foundations, floors, doors, and
furnishings of dwellings.



METHODS OF DESTROYING RATS.


A compilation of all the methods of destroying rats practiced in
historic times would fill a volume. Unfortunately, the greater number of
them are worthless or impracticable. Few have more than temporary effect
upon their numbers, and even the best of them fail unless persistently
applied. Conditions vary so much that no one method of dealing with this
pest is applicable in all cases. Among the more important measures to be
recommended for actively combating the brown rat are: (1) Poisons; (2)
traps; (3) ferrets; (4) fumigation, and (5) rat-proof construction of
buildings.


POISONING.

~Barium Carbonate.~--One of the cheapest and most effective poisons for
rats and mice is barium carbonate, or barytes. This mineral has the
advantage of being without taste or smell; and, in the small quantities
used in poisoning rats and mice, is harmless to larger animals. Its
action on rodents is slow, but reasonably sure, and has the further
advantage that the animals before dying, if exit be possible, usually
leave the premises in search of water. Its employment in houses,
therefore, is rarely followed by the annoying odor which attends the use
of the more virulent poisons.

The poison may be fed in the form of a dough made of one-fifth barytes
and four-fifths meal, but a more convenient bait is ordinary oatmeal,
with about one-eighth of its bulk of barytes, mixed with water into a
stiff dough; or the barytes may be spread upon bread and butter or
moistened toast. The prepared bait should be placed in rat runs, a small
quantity at a place. If a single application of the poison fails to
drive all rats from the premises, it should be repeated with a change of
bait.

~Strychnine.~--Strychnine is a more virulent poison, but its action is so
rapid that the animals often die upon the premises, a circumstance which
prohibits its use in occupied dwellings. Elsewhere strychnine may be
employed with great success. Dry strychnine crystals may be inserted in
small pieces of raw meat, Vienna sausage, or toasted cheese, and these
placed in the rat runs; or oatmeal may be wet with a strychnine sirup,
and small quantities laid out in the same way.

Strychnine sirup is prepared as follows: Dissolve a half ounce of
strychnia sulphate in a pint of boiling water; add a pint of thick
sugar sirup and stir thoroughly. A smaller quantity of the poison may be
prepared with a proportional quantity of water. In preparing the bait it
is necessary that all the oatmeal should be moistened with sirup. Wheat
is the most convenient alternative bait. It should be soaked over night
in the strychnine sirup.

~Other Poisons.~--The two poisons most commonly used for rats and mice are
arsenic and phosphorus, nearly all commercial preparations containing
one or the other as a basis. While experiments prove that rats have
great powers of resistance to arsenic, it may sometimes be used
advantageously as an alternative poison. Preparations of phosphorus sold
by druggists are often too weak to be effective; and home-made mixtures,
when of sufficient strength, are dangerous, as rats may carry the baits
into walls or crannies and thus cause fires. For these and other reasons
the Biological Survey does not recommend preparations containing
phosphorus.

~Poison in the Poultry House.~--For poisoning rats in buildings and yards
occupied by poultry, the following method is recommended: Two wooden
boxes should be used, one considerably larger than the other, and each
having two or more holes in the sides large enough to admit rats. The
poisoned bait should be placed on the bottom and near the middle of the
larger box, and the smaller box should then be inverted over it. Rats
thus have free access to the bait, but fowls are excluded.


TRAPPING.

Trapping, if persistently followed, is one of the most effective methods
of destroying rats. The improved modern traps with a wire fall released
by a baited trigger and driven by a coiled spring have marked advantages
over the old forms, and many of them may be used at the same time. These
traps, sometimes called guillotine traps, are of many designs, but the
more simply constructed are to be preferred. Probably those made
entirely of metal are the best, as they are less likely to absorb and
retain odors.

In illustration of the effectiveness of traps, it may be related that a
year or two ago a large department store in Washington experienced heavy
losses of gloves, lace curtains, and other merchandise from rat
depredations. For several months the damages amounted to from $10 to $30
nightly. After many unsuccessful attempts to abate the nuisance the
managers were advised to try the improved traps. As a result 136 rats
were killed during the first twenty nights, when the losses practically
ceased, and the method has been continued in the store ever since with
satisfactory results.

Guillotine traps should be baited with small pieces of Vienna sausage
(Wienerwurst) or bacon. The trigger wire should be bent inward to bring
the bait into proper position to permit the fall to strike the rat in
the neck, as shown in the illustration (fig. 1).

Other excellent baits for rats are oatmeal, toasted cheese, toasted
bread (buttered), and sunflower or pumpkin seeds. When seed, grain, or
meal is used with a guillotine trap, it may be placed on the trigger
plate, or the trigger wire may be bent outward and the bait sprinkled
under it.

[Illustration: FIG. 1.--Method of baiting guillotine trap.]

Wire cage traps (French) also are useful for catching rats, but in the
long run the kinds recommended above are much more effective. While
trapping, all other food should be removed and the trap bait should be
changed often. Rats are very suspicious, and baits and traps should be
handled as little as possible. Increased success may be secured both in
trapping and poisoning if the rats are fed for a night or two with the
kinds of food to be used for bait.


USE OF FERRETS AND DOGS.

A ferret is useful for the purpose of driving rats out of burrows and
other hiding places so that dogs can capture them. An experienced person
with dogs and ferrets trained to work together can kill many rats when
they are numerous. But the amateur ferreter is likely to be greatly
disappointed.

In the rice fields of the far East the natives build numerous piles of
brush and rice straw and leave them for several days until many rats
have taken shelter in them. A portable bamboo inclosure several feet in
height is then set up around each pile in succession and the straw and
brush are thrown out over the top while dogs and men kill the trapped
rodents. Large numbers are killed in this way, and the plan with
modifications may be utilized in America with satisfactory results. A
wire netting of fine mesh may be used for the inclosure. The scheme is
applicable at the removal of grain, straw, or hay stacks, as well as
brush piles.


FUMIGATION.

Rats may be destroyed in their burrows in the fields, and, still more
important, in levees and rice-field dikes, by the use of carbon
bisulphid. A wad of cotton or other absorbent material is saturated with
the liquid and pushed into the burrow, the opening being packed with
soil to prevent escape of the gas. All animals in the burrow are
asphyxiated. Fumigation about buildings is not so effective, as the gas
can not readily be confined.



RAT-PROOF CONSTRUCTION.


The best way of excluding rats from buildings, whether in the city or
country, is by the use of cement in construction. As the advantages of
this material are coming to be generally understood, its use is rapidly
extending to all kinds of building. Dwellings, dairies, barns, stables,
chicken houses, ice houses, bridges, dams, silos, tanks, cisterns,
root-cellars, hotbeds, sidewalks, and curbs are now often made wholly of
concrete. In constructing dwelling houses the additional cost of making
the foundations rat-proof is slight as compared with the advantages. The
cellar walls should have concrete footings and the walls themselves be
laid in cement mortar. The cellar floor should be of "medium" rather
than "lean" concrete, and all water and drain pipes should be surrounded
with concrete. Even an old cellar may be made rat-proof at comparatively
small expense. Rat holes may be permanently closed by a mixture of
cement, sand, and broken glass or sharp bits of stone.

Rat-proof granaries, corncribs, and poultry houses may be constructed by
a liberal use of concrete in the foundations and floors.

Rats, mice, and sparrows may be excluded from corncribs by the use of
either an inner or an outer covering of fine-mesh wire netting
sufficiently heavy to resist the teeth of rats.

The common custom of setting corncribs upon posts with inverted pans at
the top often fails because the posts are not long enough to insure that
the lower cracks of the structure are beyond jumping reach of rats. The
posts should project at least 3 feet above the surface of the ground.



NATURAL ENEMIES OF RATS.


The value of carnivorous mammals and the larger birds of prey in
destroying rats should be more fully recognized, especially by the
farmer and the game preserver. Chief among the animals that are useful
in destroying these rodents are the fox, skunk, and weasel, and the
larger species of owls and hawks. Rats destroy more poultry and game,
both eggs and young chicks, than all the birds and wild mammals named
combined, yet some of our most useful birds of prey and carnivorous
mammals are persecuted almost to the point of extinction. An enlightened
public sentiment should cause the repeal of all bounties on these
animals and afford protection to the majority of them.



CONCLUSIONS.


By the persistent use of traps, occasional resort to poison, and the
exercise of forethought in the construction of farm buildings so as to
minimize the opportunities for harborage, farmers and others may prevent
the greater part of the loss and annoyance they now experience from rat
depredations. The same statement applies in great measure to city and
village conditions. Hence cooperation in the warfare on rats is
particularly important and can not be too strongly urged.





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