If you hear scratching, scurrying or gnawing above the ceiling after the house goes quiet, you're not imagining it. In Los Angeles, the usual source is the roof rat, a climber that nests up high and is most active at night.
What the sound tells you
- Fast scurrying and light scratching, mostly after dark: typical of roof rats or mice. Both are nocturnal, so activity tends to start soon after sunset and again before dawn.
- Gnawing: a steady scraping or chewing sound. Rodents gnaw constantly to keep their teeth worn down, on wood, wiring and ducts.
- Heavier thumping or rolling sounds: rats sometimes drag or roll food, like a fruit from the garden. Very heavy movement can also be a larger animal such as an opossum or raccoon.
- Noise in the walls rather than the attic: rodents travel inside wall cavities between the attic and lower floors.
Check for these signs
- Droppings. Rat droppings are about half an inch long with blunt ends. Mouse droppings are smaller, about a quarter of an inch, and pointed. Look in the attic near the hatch, in the garage and under sinks.
- Gnawed fruit. Half-eaten oranges or avocados still hanging on the tree are a classic roof rat sign in Los Angeles yards.
- Grease marks. Dark smudges along beams, pipes or the top of a fence where rodents run the same route every night.
- Chewed wiring or insulation in the attic, or chewed wires under the car hood.
- How they're getting up there. Look at palms, ivy and tree branches touching the roof, and at vent screens along the roofline.
Don't poke around in a crawlspace or attic full of droppings without protection. Never sweep or vacuum droppings dry: wet them with a disinfectant first and wear gloves.
What to do first
- Don't rely on poison. A poisoned rodent often dies inside a wall or ceiling, out of reach, and most anticoagulant rat poisons are now banned for home use in California anyway.
- Don't seal the obvious hole and stop there. Rats and mice that are already inside need to be removed, or they'll chew a new way out. And a home usually has more than one way in.
- Book an inspection. A licensed technician checks the roofline, attic, vents and crawlspace, photographs every entry point, and gives you a written plan before any work starts.
Why it's worse in the fall
Roof rats breed all year in Southern California, but they move into homes most from late summer through fall, then nest in attics through the winter rains. If you're hearing it in October, it usually won't stop on its own.
More guides
- California's rat poison ban, explained for homeowners
- Roof rats vs Norway rats: which one is in your home?
This guide is general information, not a substitute for an on-site inspection. Sealwell is a referral service, not a contractor.
