While the use of poison is the best and quickest way to get rid of rats
and mice, the odor from the dead animals makes the method impracticable
in occupied houses. Poisons may be effectively used in barns, stables,
sheds, cribs, and other outbuildings.
=Caution.=--In the United States there are few laws which prohibit the
laying of poisons on lands owned or controlled by the poisoner. Hence it
is all the more necessary to exercise extreme caution to prevent
accidents. In several States notice of intention to lay poison must be
given to persons living in the neighborhood. Poison for rats should
never be placed in open or unsheltered places. This applies particularly
to strychnin or arsenic on meat. _Packages containing poisons should
always bear a warning label and should not be kept where children might
reach them._
Among the principal poisons that have been recommended for killing rats
and mice are barium carbonate, strychnin, arsenic, phosphorus, and
squills.
=Barium carbonate.=--One of the cheapest and most effective poisons for
rats and mice is barium carbonate. This mineral has the advantage of
being without taste or smell. It has a corrosive action on the mucous
lining of the stomach and is dangerous to larger animals if taken in
sufficient quantity. In the small doses fed to rats and mice it would be
harmless to domestic animals. Its action upon rats is slow, and if exit
is possible the animals usually leave the premises in search of water.
For this reason the poison may frequently, though not always, be used in
houses without disagreeable consequences.
Barium carbonate may be fed in the form of dough composed of four parts
of meal or flour and one part of the mineral. A more convenient bait is
ordinary oatmeal with about one-eighth of its bulk of the mineral, mixed
with water into a stiff dough. A third plan is to spread the barium
carbonate upon fish, toasted bread (moistened), or ordinary bread and
butter. The prepared bait should be placed in rat runs, about a
teaspoonful at a place. If a single application of the poison fails to
kill or drive away all rats from the premises, it should be repeated
with a change of bait.
=Strychnin.=--Strychnin is too rapid in action to make its use for rats
desirable in houses, but elsewhere it may be employed effectively.
Strychnia sulphate is the best form to use. The dry crystals may be
inserted in small pieces of raw meat, Vienna sausage, or toasted cheese,
and these placed in rat runs or burrows; or oatmeal may be moistened
with a strychnin sirup and small quantities laid in the same way.
Strychnin 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 may be prepared with a
proportional quantity of water and sirup. In preparing the bait it is
necessary to moisten all the oatmeal with the sirup. Wheat and corn are
excellent alternative baits. The grain should be soaked overnight in the
strychnin sirup.
=Arsenic.=--Arsenic is probably the most popular of the rat poisons,
owing to its cheapness, yet our experiments prove that, measured by the
results obtained, arsenic is dearer than strychnin. Besides, arsenic is
extremely variable in its effect upon rats, and if the animals survive a
first dose it is very difficult to induce them to take another.
Powdered white arsenic (arsenious acid) may be fed to rats in almost any
of the baits mentioned under barium carbonate and strychnin. It has been
used successfully when rubbed into fresh fish or spread on buttered
toast. Another method is to mix twelve parts by weight of corn meal and
one part of arsenic with whites of eggs into a stiff dough.
An old formula for poisoning rats and mice with arsenic is the
following, adapted from an English source:
Take a pound of oatmeal, a pound of coarse brown sugar, and a spoonful
of arsenic. Mix well together and put the composition into an earthen
jar. Put a tablespoonful at a place in runs frequented by rats.
=Phosphorus.=--For poisoning rats and mice, phosphorus is used almost as
commonly as arsenic, and undoubtedly it is effective when given in an
attractive bait. The phosphorus paste of the drug stores is usually
dissolved yellow phosphorus, mixed with glucose or other substances. The
proportion of phosphorus varies from one-fourth of 1 per cent to 4 per
cent. The first amount is too small to be always effective and the last
is dangerously inflammable. When homemade preparations of phosphorus are
used there is much danger of burning the person or of setting fire to
crops or buildings. In the Western States many fires have resulted from
putting out homemade phosphorus poisons for ground squirrels, and entire
fields of ripe grain have been destroyed in this way. Even with
commercial pastes the action of sun and rain changes the phosphorus and
leaches out the glucose until a highly inflammable residue is left.
It is often claimed that phosphorus eaten by rats or mice dries up or
mummifies the body so that no odor results. The statement has no
foundation in fact. No known poison will prevent decomposition of the
body of an animal that died from its effects. Equally misleading is the
statement that rats poisoned with phosphorus do not die on the premises.
Owing to its slower operation, no doubt a larger portion escape into the
open before dying than when strychnin is used.
The Biological Survey does not recommend the use of phosphorus as a
poison for rodents.
=Squills.=--The squill, or sea leek,[6] is a favorite rat poison in many
parts of Europe and is well worthy of trial in America. It is rapid and
very deadly in its action, and rats seem to eat it readily. The poison
is used in several ways. Two ounces of dry squills, powdered, may be
thoroughly mixed with eight ounces of toasted cheese or of butter and
meal and put out in runs of rats or mice. Another formula recommends two
parts of squills to three parts of finely chopped bacon, mixed with meal
enough to make it cohere. This is baked in small cakes.
=Poison in poultry houses.=--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 one 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
smaller box, and the larger box should then be inverted over it. Rats
thus have free access to the bait, but fowls are excluded.