d. Rats prefer to travel and hunt for food at night. They are creatures of habit
and almost always travel from their nests to their food sources and to the outside over
the same paths. Perhaps for protection, their paths usually are in narrow, out of the
way places, such as overhead pipes and beams, or along walls. When rats run from
place to place, they hug the wall. Rat runs are easy to find because dirt and oil from the
hair on the rat rub off and darken the surfaces that they touch.
e. Rodents are rarely seen except in heavy infestations. When you see a live or
dead rodent, you can be sure that there are a number of others in the area. It is
necessary to continually monitor for signs that indicate their presence. The presence of
droppings, or feces, is one of the signs. House mouse feces are only 1/8 inch in length.
Rat feces are from 1/2 to 3/4 inch in length and up to 1/4 inch in diameter. Older feces
are brownish in color and often fall apart when touched with a pencil. If the droppings
are moist, black and shiny, and hold together, a rodent has recently been in the vicinity.
Rodent runways are usually along walls, steps, and rafters, when they move from their
nests to sources of food. They leave rubmarks, which are visible streaks from their
bodies. Rodents gnaw to reach sources of food. Their incisor teeth are so strong that
they have gnawed through paperboard, sacks, and wood. If gnawings are recent, the
inspector should notice teeth marks. Some people have spread talc in areas of
suspected rodent infestation. Talc will make new tracks visible. Normally, tracks may
be covered with dust, though sometimes sharp and distinct, if they are recent. Regular
checks around the outside of the building may turn up rat burrows (rat-sized holes). It
must be determined if they are fresh or old, because you want to allow the rats inside a
way to get out before closing them up. Holes of 1/4 inch anyplace in a building will
permit entry of rodents. Such openings must be repaired immediately. When there is
other evidence of rodent presence, the use of ultraviolet light (Wood's light) is
recommended to locate urine residue and stains.
The second phase in controlling rodents is the use of chemicals, specifically
rodenticides, to control those rodents that may have gained entrance to the area,
whether within the buildings or on the surrounding premises.
a. Poisoning is probably the best way to get rid of rodents after proper sanitation
and rodent proofing. However, poisoning will have to be repeated from time to time,
because it only kills the rodents that are present at the time of poisoning and does not
prevent other rodents from entering later. Poisoning should be started before proofing
an existing building to ensure dying rodents are not caught inside the buildings with no
chance of escape. Some of the most common rodenticides and fumigants are