The gaps rodents use to get inside
Rats and mice get into apartments through gaps and holes in the building — around pipes, vents, and wiring, under doors, through foundation cracks, and via shared walls. Mice can squeeze through an opening as small as a dime.
Rodents are drawn to warmth, water, and food, and they are remarkably good at finding a way in. Common entry points include the spaces where plumbing and cables pass through walls, gaps beneath exterior doors, uncovered vents, and cracks around the foundation or windows. In multi-unit buildings, they also travel from one apartment to the next.
Because sealing these openings is part of maintaining the structure, closing off entry points is generally the landlord's responsibility. Trapping the rodents inside without sealing the gaps just invites new ones. If you can see how rodents are getting in and your landlord will not seal it, a free review can help you understand what they should be doing.
This is general information about California tenant rights, not legal advice. Every situation is different.