Signs include feces, bitten through packages, and a distinctive scent.
Explanation:
Mice are not particularly clean and can cause an unpleasant smell. A worker might notice that scent. Mice leave behind small feces pieces about the size of a grain of rice. They also chew through various materials such as boxes or packages. Workers can be on the lookout for any such signs. Of course, actually spotting a mouse is the surest method of identifying that mice are present.
