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Bats do not commonly migrate far from their homes,
These then are the more important of the characteristics of the
Indian house rat which plays so important a part in the spread of
plague. Successful efforts at rat elimination and rat destruction
necessitate a display of intelligence, energy, persistence and a lively
understanding of their habits and customs as outlined above.
Before considering measures in detail it may be worth while to
refer to the economic aspects of the case. An adult rat consumes
upwards of |- oz. of grain each day. Let us take the case of an
Indian town with a human population of a quarter of a million people.
Such a town at a very low estimate will have a rat population
amounting to half a million. Let us suppose that the rats of this
town have a preference for a grain selling at ten seers for the
rupee. The rat population of this town would consume grain each
day to the value of Us. 1,170 and at the same time do a vast amount
of damage to human property of other kinds. (This sum is equivalent
to He. 1-11-0 per head of population per annum, an amount which if
-devoted to public health would insure freedom from plague and many
other diseases as well.) Truly the inhabitants of this country in so
gladly suffering the rat suffer in other ways than those of disease and
death,
2. Rat elimination.—Energetic and sustained rat-destruction
campaigns, carried out on lines such as those that will be described
hereafter and with due attention to detail, will do much towards
keeping the rat population at a low level with a consequent markedly
diminished risk of plague-infection and the certainty of a much
milder epidemic, should the disease gain a foothold, than would
otherwise be the case. Such measures have the great disadvantage
that they necessitate sustained effort which is very difficult to secure
in India when a few years' freedom from plague so commonly en-
genders a false sense of security. If half-heartedly carried out, the
results will be most disappointing and the number of those who claim
that rat-destruction campaigns are useless, and consequently waste of
funds, will be increased.
Moreover, rat-destruction campaigns are of only temporary benefit
and it is necessary first to consider whether the houses, habits, and
customs of the people cannot be so modified as to render the associa-
tion -between the rat and human population less close than it is at
present. As things are there is no limit to the amount of food a,nd
shelter that the average Indian house affords to the rat. In this
connexion it would be well to draw attention to the fact that the two
terms { rat-proof ' and ' rat-free ' as applied to dwellings and store-
houses are by no means synonymous. Very little advantage is gained
if the floors, walls and roof of buildings be so constructed as to make it
impossible for rats to burrow therein, if such erections offer no lack of
food and shelter to rats and if ingress and egress through doors and
other apertures be not prevented by some special device. This word of
warning is very necessary : in many parts of India one can see buildings
that have been' made ' rat-proof,' harbouring, all the same, a very
large number of rats. Small wonder that such laudable endeavours
to abolish plague have met with a degree of success in no way
commensurate with the comparative large outlays that some such
schemes have involved,