Last Updated: March 2026 | Reviewed by The PCC Research Team
A rat is not just a rat. In California, rat infestations are caused by two entirely different species with opposing biological habits. If you try to treat a climbing rat with ground-level traps, you will fail to stop the infestation.
To effectively eliminate a colony and permanently seal your home, you must first identify which species has breached your property. This sub-hub provides the specific identification and eradication protocols for the most destructive rats in the state.
Step 1: Identify Your Invader
Select the option below that best matches the evidence you are finding on your property.
The Undeniable Signs of a Rat Infestation
Because rats are nocturnal and highly cautious (neophobic), you will rarely see them wandering around during the day unless the colony is massive and they are fighting for food. Instead, look for these three distinct indicators:
- The Droppings: Rat droppings are large (1/2 to 3/4 inch), usually blunt at the ends, and found in specific clustered areas (unlike mouse droppings, which are small and scattered everywhere).
- The Gnaw Marks: A rat’s front teeth never stop growing. To file them down, they will chew on structural wood, PVC plumbing pipes, and even concrete edges. Their gnaw marks look like dual scratches measuring about 1/8 inch wide.
- The Scratching Noises: You will hear thumping, running, and scratching between your drywall or above your ceiling, specifically between dusk and dawn.
Rats have incredibly poor eyesight. To navigate safely in the dark, they run the exact same routes every single night, dragging their bodies against the baseboards or walls so their whiskers stay engaged. Over time, the dirt and natural oils (sebum) in their fur leave dark, greasy smudges on the walls. If you find a dark, greasy trail along a floorboard or around a gap under a door, you have found an active runway. That is exactly where you should place your traps.
Why You Cannot Ignore Them
A rat infestation is not a problem that will resolve itself. They breed exponentially, and the biological hazards escalate quickly.
Rats are vectors for numerous pathogens. Through their urine and feces, they can transmit Leptospirosis and Salmonellosis. As they move through the structural voids of your home, they shed dander and hair, and if they chew into your HVAC ducting, those contaminants are blown directly into your living room.
If you suspect an infestation, you must act fast to seal the exterior and begin trapping before the colony establishes deep nesting sites within your insulation.
Stop the Damage. Verify Your Contractor.
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