The effect of an abundance of food on the breeding of rodents should be
kept in mind. Well-fed rats mature quickly, breed often, and have large
litters. Poorly fed rats, on the contrary, reproduce less frequently and
have smaller litters. In addition, scarcity of food makes measures for
destroying the animals far more effective.
=Merchandise in stores.=--In all parts of the country there is a serious
economic drain in the destruction by rats and mice of merchandise held
for sale by dealers. Not only foodstuffs and forage, but textiles,
clothing, and leather goods are often ruined. This loss is due mainly to
the faulty buildings in which the stores are kept. Often it would be a
measure of economy to tear down the old structures and replace them by
new ones. However, even the old buildings may often be repaired so as to
make them practically rat-proof; and foodstuffs, as flour, seeds, and
meats, may always be protected in wire cages at slight expense. The
public should be protected from insanitary stores by a system of rigid
inspection.
[Illustration: FIG. 4.--Floor plan of rat-proof corncrib shown in figure
3.]
=Household supplies.=--Similar care should be exercised in the home to
protect household supplies from mice and rats. Little progress in
ridding the premises of these animals can be made so long as they have
access to supplies of food. Cellars, kitchens, and pantries often
furnish subsistence not only to rats that inhabit the dwelling, but to
many that come from outside. Food supplies may always be kept from rats
and mice if placed in inexpensive rat-proof containers covered with wire
netting. Sometimes all that is needed to prevent serious waste is the
application of concrete to holes in the basement wall or the slight
repair of a defective part of the building.
=Produce in transit.=--Much loss of fruits, vegetables, and other
produce occurs in transit by rail and on ships. Most of the damage is
done at wharves and in railway stations, but there is also considerable
in ships' holds, especially to perishable produce brought from warm
latitudes. Much of this may be prevented by the use of rat-proof cages
at the docks, by the careful fumigation of seagoing vessels at the end
of each voyage, and by the frequent fumigation of vessels in coastwise
trade; but still more by replacing old and decrepit wharves and station
platforms with modern ones built of concrete.
Where cargoes are being loaded or unloaded at wharves or depots, food
liable to attack by rats may be temporarily safeguarded by being placed
in rat-proof cages, or pounds, constructed of wire netting. Wooden boxes
containing reserve food held in depots for a considerable time or
intended for shipment by sea may be made rat-proof by light coverings of
metal along the angles. This plan has long been in use to protect naval
stores on ships and in warehouses. It is based on the fact that rats do
not gnaw the plane surfaces of hard materials, but attack doors,
furniture, and boxes at the angles only.
=Packing houses.=--Packing houses and abattoirs are often sources from
which rats secure subsistence, especially where meats are prepared for
market in old buildings. In old-style cooling rooms with double walls of
wood and sawdust insulation, always a source of annoyance because of rat
infestation, the utmost vigilance is required to prevent serious loss of
meat products. On the other hand, packing houses with modern
construction and sanitary devices have no trouble from rats or mice.
=Garbage and waste.=--Since much of the food of rats consists of garbage
and other waste materials, it is not enough to bar the animals from
markets, granaries, warehouses, and private food stores. Garbage and
offal of all kinds must be so disposed of that rats can not obtain them.
In cities and towns an efficient system of garbage collection and
disposal should be established by ordinances. Waste from markets,
hotels, cafes and households should be collected in covered metal
receptacles and frequently emptied. Garbage should never be dumped in or
near towns, but should be utilized or promptly destroyed by fire.
Rats find abundant food in country slaughterhouses; reform in the
management of these is badly needed. Such places are centers of rat
propagation. It is a common practice to leave offal of slaughtered
animals to be eaten by rats and swine, and this is the chief means of
perpetuating trichinae in pork. The law should require that offal be
promptly cremated or otherwise disposed of. Country slaughterhouses
should be as cleanly and as constantly inspected as abattoirs.
Another important source of rat food is found in remnants of lunches
left by employees in factories, stores, and public buildings. This food,
which alone is sufficient to attract and sustain a small army of rats,
is commonly left in waste baskets or other open receptacles. Strictly
enforced rules requiring all remnants of food to be deposited in covered
metal vessels would make trapping far more effective.
[Illustration: FIG. 5.--Guillotine trap made entirely of metal.]
Military training camps, unless subjected to rigid discipline in the
matter of disposal of garbage and waste, soon become centers of rat
infestation. Waste from camps, deposited in covered metal cans and
collected daily, should be removed far from the camp itself and either
burned or utilized in approved modern ways.