Reading the signs: what happens on site when no one is around
Droppings, gnaw marks, tracks in dust, and smell are more accurate indicators of how many pests there are and how long they have been present than a single sighting.
Seeing a rodent in a warehouse during the day is rare and generally a bad sign: when population numbers are high, the animals are forced to emerge at unusual times. Usually, however, you have to rely not on sightings but on signs, and these are generally quite clear.
Droppings are the main source of information. Mouse droppings are the size of a grain of rice; rat droppings can be up to a centimeter and a half long. Fresh droppings are dark and soft; old ones are grey, dry, and crumble under pressure. This reveals whether the site is currently active or the signs remain from the previous season.
Gnaw marks. A fresh gnaw mark on wood is lighter than the surrounding surface; an old one is darker. The pattern of damage is also revealing: neat, rounded holes in packaging are more often made by mice, while large, ragged holes and burrows indicate rats.
Grease marks. Rats follow the same routes along walls and leave dark, glossy streaks on baseboards, corners, and pipes. These marks are the most reliable guide to where bait points should be placed — the route is literally visible.
Tracking patches. This is a very simple technique: dust suspected areas with a thin layer of flour or talc and inspect them a day later. Pawprints and tail marks will confirm both the presence of rodents and their direction of travel.
The practical value is that an inspection provides not only a yes-or-no answer but also a map. Bait points placed along identified routes are several times as effective as points distributed evenly "just in case."
