The telltale signs rodents leave behind
Signs of a rodent infestation include droppings (small dark pellets), gnaw marks on food packaging or wood, scratching or scurrying sounds in the walls and ceiling at night, nests of shredded material, greasy rub marks, and a musky smell.
Mice and rats are mostly active after dark, so noises in the walls at night are a common early clue. Look for droppings along baseboards, inside cabinets, and behind appliances; chewed packaging or wiring; small gnawed openings; and dark rub marks where rodents travel the same paths. Rats tend to leave larger droppings than mice.
The more of these signs you find, the more established the infestation — and the more likely it needs professional treatment rather than a couple of traps. If you are seeing several signs, photograph them and report the problem to your landlord in writing so there is a record of when it started.
This is general information about California tenant rights, not legal advice. Every situation is different.