Roof rats and Norway rats are the two rat species in Los Angeles homes and businesses, and they live at different heights. The roof rat is slim and long-tailed, and it climbs into trees, ivy, and attics. The Norway rat is heavier and blunt-nosed, and it burrows at ground level. The species decides where traps go and which openings get sealed. A third animal, the house mouse, is often mistaken for a young rat.
How do I tell a roof rat from a Norway rat?
Check the tail first. Pulled forward over the back, a roof rat's tail reaches at least to the snout, because it is longer than the head and body combined. A Norway rat's tail reaches only to the middle of the skull. UC IPM lists the other differences:
- Weight and build. Roof rats are sleek and agile at 5 to 10 ounces. Norway rats are large and robust at 7 to 18 ounces.
- Tail color. Uniformly dark on a roof rat. Dark on top and pale underneath on a Norway rat.
- Ears. Roof rat ears reach the eyes when folded forward. Norway rat ears do not.
- Muzzle. Pointed on the roof rat, blunt on the Norway rat.
- Belly. Gray to white on the roof rat, mostly gray on the Norway rat.
Fur color will not settle it. UC IPM's identification table does not list fur at all, and its photos show light brown fur on both species.
What do roof rat, Norway rat, and mouse droppings look like?
Length separates the three animals. Cornell's IPM program puts house mouse droppings at 1/8 to 1/4 inch, roof rat droppings at about 1/2 inch, and Norway rat droppings at 3/4 to 1 inch. Fresh droppings are moist, soft, and dark. Old droppings are dull, grayish, and crumble when stepped on.
Shape is only a hint; Cornell describes all rodent droppings as cylindrical with pointed to rounded edges. Droppings along ground-floor walls, steps, and burrow openings point to Norway rats, which keep one side against a vertical surface as they travel. Droppings in attic insulation, ceiling voids, and cabinets point to roof rats. Dark, greasy rub marks along a wall or beam show a runway in regular use.
Treat droppings as a health risk. LA County's Vector Management Program has found local rodents carrying the bacteria that cause murine typhus and plague, as well as hantaviruses. Wear gloves and wet droppings with a household disinfectant before wiping them up. Never sweep or vacuum dry droppings; the CDC warns this puts tiny virus-carrying droplets into the air.
Where does each rat live in Los Angeles?
Roof rats live high and Norway rats live low. UC IPM describes roof rats nesting above ground in shrubs, trees, and dense vegetation such as ivy. Indoors they prefer attics, wall voids, ceiling voids, and cabinets. They eat avocados and citrus on the tree, travel 300 feet or more for food, and run along utility lines and fence tops at night.
Norway rats dig burrows along building foundations, under rubbish and woodpiles, and around gardens. Indoors they stay mostly in basements and ground floors. LA County Public Health describes an ongoing battle against Norway rats in downtown Los Angeles. Watch for freshly disturbed soil at the base of foundations and along sidewalks and driveways.
Hillside and canyon cities such as Calabasas, La Cañada Flintridge, and Palos Verdes Estates get rats moving in from open space. We cover those entry points in why rodents enter hillside homes. The Rio Hondo and San Gabriel River corridors near our El Monte office sustain rodent pressure, and older San Gabriel Valley housing gives both species gaps to exploit.
Why does the species change trap placement?
Because traps only work on the travel route, and the two species travel at different heights. For Norway rats, UC IPM says to set traps close to walls, behind objects, in dark corners, and where droppings or smudge marks appear. Position them at right angles to the wall, trigger end nearly touching it. Roof rat traps often go both on the ground and above it: ledges, shelves, branches, fences, pipes, or overhead beams, each secured so the snap works.
UC IPM says a heavily infested home may need a dozen or more traps, spaced 10 to 20 feet apart, each with a pea-sized dab of bait. Roof rats carry food away to eat elsewhere, while Norway rats often feed where they forage. Tie solid bait to the trigger with thread or fine wire, or glue it.
Indoors, LA County Public Health prefers snap traps, because a poisoned rat can die in an inaccessible spot and bring odors and flies. California also prohibits most uses of first- and second-generation anticoagulant rodenticides, which UC IPM says are unavailable for structural pest control without a special exemption. We compare trapping and exclusion in rodent exclusion vs. baiting.
Why does the species change exclusion work?
Because the entry points sit at different heights. Both species need the same standard: seal every opening larger than 1/4 inch with 1/4-inch metal hardware cloth or sheet metal. Rats chew through plastic, foam, wood, and caulk. A young rat can squeeze under a door with a 1/2-inch gap.
Roof rat exclusion works from the roofline down:
- Screen vents with heavy galvanized metal mesh, never lightweight chicken wire.
- Seal openings where pipes, cables, and wires enter the walls or foundation.
- Remove overhanging limbs within 6 feet of the roof, and thin or remove climbing ivy.
- Remove fallen fruit and nuts promptly.
Norway rat exclusion works from the slab up:
- Screen foundation vents and close gaps where conduit meets the wall.
- Fit door sweeps or weather stripping so no threshold gap exceeds 1/4 inch.
- Destroy active burrows, and remove cast-off items or raise them 18 inches off the ground.
PesPro's rodent exclusion service seals gaps, vents, utility penetrations, and foundation cracks, as an add-on to Rodent Control or as a standalone job.
Is it a mouse or a young rat?
Look at the head and feet. UC IPM notes that very young rats have large heads and feet in proportion to their bodies, while an adult mouse's are proportionately much smaller. Cornell adds that mice have large ears and eyes, a pointier nose, and a uniform body color, while Norway rats tend to be two-toned. An adult house mouse weighs about half an ounce and runs 5 to 7 inches including the tail.
The mouse changes the plan more than the rat does:
- Mice squeeze under gaps 1/4 inch tall and through openings 3/8 inch wide, so the 1/4-inch standard has no slack.
- Mice seldom travel more than 30 feet from the nest, so traps go no more than about 10 feet apart, sometimes in pairs.
- Gnaw marks from an adult mouse measure 1 to 2 millimeters wide per pair of teeth. An adult rat leaves marks 3.5 to 4 millimeters wide.
A female mouse can raise 5 to 10 litters a year, so a small sighting rarely stays small. Our Rodent Control program combines trapping, monitoring, and prevention, and the written quote is free. Rodents are covered by our 30-day guarantee: if the problem reappears within 30 days, the third visit is on us.
Frequently asked questions
Can roof rats and Norway rats infest the same building?
Yes. UC IPM reports that both species are present in almost all California cities and can occupy the same structure. When they do, Norway rats typically occupy the basement and ground floors while roof rats occupy the upper floors. So an inspection must check the attic and crawl space, not just the kitchen.
How fast can you come out, and what does it cost?
The written quote is free. Same-day service is available for an extra fee and depends on the day's route. Our 24/7 emergency line is (323) 472-5329, and our bilingual team covers Los Angeles and San Bernardino counties. Pricing depends on property size, pest type, and service frequency; start on the contact page.
Should I worry about fleas when rats are removed?
Sometimes. LA County's Vector Management Program notes that rodent fleas seek another host after the rodent dies. It recommends controlling fleas in an approved manner before trapping or baiting, especially where plague or murine typhus is a concern. Mention any flea activity when you book so we can coordinate flea and tick control with the rodent work.