RAT SIGNS
LIGHT
MEDIUM
HEAVY
OBSERVED
1-20
21-50
OVER 5O
Many; two or
more sizes;
Moderate to many;
Few to moderate in
runways in dusty
Usually of two or
Tracks
number; usually all
areas usually
more distinct sizes.
of one size.
slick and not
dusty.
Many; usually of
Some always seen
several sizes;
in two to six to
None or few groups
Fresh
small to large
eight areas;
observed; generally
Droppings
and in at least six
usually two distinct
all of same size.
locations.
sizes.
Several distinct;
Many; more than
one or more indicating
Active
None or few and
one heavily
heavy
Runs
relatively indistinct.
traveled run.
travel.
Fresh
Usually several
Many instances
None to few nightly.
Gnawing
instances nightly.
nightly.
Often one or
more
None to two by day
None by day except
Live rats
seen by quiet,
unless harborage is
cleanup and harborage
Seen
close observation,
opened up.
removal.
even in daytime.
Figure 2-4. Degree of infestation.
c. Food Sources. During the survey, particular attention must be given to all
potential rodent food sources, such as dining facilities, commissaries, grain storage
warehouses, garbage cans, and garbage and refuse disposal areas. The large
concentration of rats at these points frequently makes them centers of infection when
rodent-borne diseases occur. Control measures directed at these spots will, therefore,
be most effective in reducing the rodent population and retarding the spread of such
diseases.
d. Harborages. It is quite important to look carefully for situations that present
the rodent with opportunities for suitable harborage. Concrete slabs at entries
(particularly if the earth is soft or has fallen away slightly beneath the slab), boxes and
garbage cans set closely against the building, piles of rubbish, holes in walls, and goods
stacked indoors without adequate aisle space to allow access during inspections are all
invitations for rodents to enter and to make their habitations.
MD0172
2-7