Figure 2-1. Rat droppings in a basement.
assuming a grayish, dusty appearance, and the droppings may crumble easily when
pressed. Droppings are found wherever rodents occur, but they are more numerous
along their runaways, near their harboring places, and in secluded corners. Droppings
may be found scattered also on the tops of goods stored in a building. The number of
droppings found in a building will depend on the rapidity of the turnover of its contents
and how frequently the building is cleaned, as well as on the size of the rodent
population. Rat urine will fluoresce under ultraviolet light, as will some other materials.
The presence of fluorescent patches in an area does not alone prove the presence of
rats.
b. Runways. Runways usually lead to some point where the rodents are
entering the building, to one of their interior harboring places, or to places where they
drink or feed. The fur of rats is covered with oil and dust; whenever they rub their
bodies against a wall, climb a pipe, or pass through a hole or barrier, they leave a
greasy deposit. (See figure 2-2). Because rats tend to follow the same end routes,
these deposits are built up until characteristic black markings result. Unused rat runs
may be distinguished from currently used ones by washing off some of the marks or by
covering a portion of the run with white paint; after a few days, new markings can be
observed easily. Active runways usually have a shiny, dust-free appearance. Little-
used runs may be dusty, with individual tracks apparent; though heavily traveled rat
turns will be slick, and no individual tracks will be observable. Sometimes the fact that a
run is no longer in use may be seen at once from the presence of unmolested cobwebs
MD0172
2-3