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How to identify it
- Sleek and smaller than the Norway rat, with a pointed muzzle and large ears that reach the eyes when folded. Weights differ by source: UC IPM gives 5 to 10 ounces; the Internet Center for Wildlife Damage Management (ICWDM) gives about 5 to 9 ounces, reaching 12.[1][4]
- The tail is longer than the head and body combined and uniformly dark.[1]
- ICWDM gives a body of 6 to 8 inches plus a 6- to 8-inch scaly tail, about 16 inches in all. The fur is soft and smooth, brown mixed with black, and the belly may be white, gray or black.[4]
- A telltale sign is oranges hollowed out through a small hole, with empty rinds left hanging on the tree.[1][6]
- Indoors, sounds in the attic at night are often the first sign. Droppings, urine and tracks on floors are less likely to be seen, because the rats may live overhead and come down to feed; in storage buildings, smudge marks along their aerial routes may be the most obvious sign.[6]
Look-alikes
| Look-alike | How to tell them apart |
|---|---|
| Norway rat | Larger and stockier with a blunt muzzle, small ears and a shorter, two-toned tail; burrows in the ground.[1] |
Where it lives
Prefers warm and coastal climates, though its range is expanding; mature landscaping and ivy provide good habitat, and in buildings it lives in attics and upper floors.[1]
Biology and life cycle
Roof rats often travel 300 feet or more for food and run along utility lines and fence tops at night.[1][5]
They prefer fruits, nuts, berries, snails and bird eggs. Litter figures differ: UC IPM gives 3 to 5 litters a year with up to 8 young each; ICWDM gives 5 to 8 young per litter and typically 3 or more litters a year, with breeding peaks in spring and fall.[1][5][6]
Young are born 21 to 23 days after mating, open their eyes at 9 to 14 days, and are independent and able to breed at about 3 months.[5]
Roof rats nest off the ground when they can and rarely dig burrows to live in. In a building with both species, ICWDM says roof rats are often found on the upper floor while Norway rats hold the ground floor or basement.[5]
They tend to avoid new objects even more than Norway rats.[1]
Damage and signs
- Rats in attics gnaw wiring and nest materials, creating fire risk, and they chew engine wiring in vehicles.[1][6]
- In homes, damage is often limited to insulation torn up for nests and gnawed wiring, and rats living under a refrigerator or freezer can disable it by chewing the wires.[6]
- In yards and orchards they eat the pulp from hanging oranges and leave the rind, eat only the rind of lemons, and strip bark from small citrus branches.[6]
Health risk
CDC says rodents such as rats carry many diseases, spread through contact with their droppings, urine or saliva, through contaminated food, and through bites, scratches, and the ticks, mites and fleas that feed on them. You cannot tell an infected rodent by looking at it.[8]
Control
Prevention
Trim trees and dense vegetation such as ivy away from the house, and pick up fallen fruit and nuts.[1]
Keep them out
Exclusion is the most successful and permanent rodent control: seal every gap larger than 1/4 inch with metal or concrete, including around pipes, vents and utility lines, and make doors, windows and screens fit tightly. Foam, plastic, rubber and wood are gnawed through.[2][1]
Because roof rats climb, seal openings above ground too, screen vents with sturdy 1/2-inch metal mesh (not chicken wire), and cover chimneys and large roof vent pipes.[1][9]
ICWDM gives a looser hole size than UC IPM: it says to plug or seal all openings greater than 1/2 inch, where UC IPM seals anything over 1/4 inch. Either way, check the roofline, since roof rats often get in from the roof or next to overhead utility lines.[7][1][5]
Traps and physical control
Place snap traps in attics and along runways; traps can stay set in attics where rats have been a problem.[1]
Set traps where roof rats travel, not only on the floor: ICWDM says to fasten them to beams, pipes, ledges and sills, put more traps above floor level than on it, and use attic and garage rafters near the activity as the best sites in homes.[7]
Before setting traps, CDC suggests baiting them unset for a while, because rats fear anything new. CDC advises against glue and live traps; ICWDM adds that glue boards are harder to place well for roof rats than for Norway rats or mice.[10][7]
Pesticides
Rodenticide baits sold to the public are limited to wax block, gel or paste baits packaged in or with ready-to-use, disposable bait stations; poisoning inside buildings can leave dead rodents in walls, which is one reason trapping is preferred indoors.[1][2]
If trapping does not end the problem, CDC says a poison bait station or professional help are the next options; poison baits must be used by the label and kept away from children and pets.[10]
Diseases and safe cleanup
Leptospirosis spreads in the urine of infected animals, and CDC names rats and mice among them; the bacteria can live in wet soil or water for weeks to months.[12]
CDC lists rats among the rodents that carry rat-bite fever, which is rare in the United States but serious without prompt antibiotics.[13]
CDC says people catch hantaviruses from rats and mice, mostly from urine, droppings and saliva, and only rarely from a bite or scratch.[14]
For attics and sheds with rat droppings, CDC's advice is to air the space out for 30 minutes first, then spray droppings and nests with disinfectant instead of sweeping or vacuuming, and bag contaminated insulation.[11]
Common questions
- How do roof rats get in the attic?
- They climb trees, wires and walls and enter through openings at roof level, so above-ground gaps must be sealed.[1][5]
- Are roof rats found in every state?
- No. ICWDM says most interior states are free of roof rats, though isolated infestations, probably from infested cargo, can turn up.[4]
- Where should I put traps for roof rats?
- Up high, along their routes: on beams, rafters, pipes and ledges, with attic and garage rafters near the activity the best spots in homes, according to ICWDM.[7]
Sources
- University of California Statewide IPM Program, “Pest Notes: Rats, Publication 74106 (revised June 2024).” ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pnrats.pdf (accessed 2026-11-11)
- University of California Statewide IPM Program, “Pest Notes: House Mouse, Publication 7483 (revised July 2025).” ipm.ucanr.edu/legacy_assets/PDF/PESTNOTES/pnhousemouse.pdf (accessed 2026-11-11)
- iNaturalist, “Rattus rattus taxon page (order and family).” www.inaturalist.org/taxa/44575 (accessed 2026-11-11)
- Internet Center for Wildlife Damage Management, “Roof Rats: Identification.” icwdm.org/species/rodents/roof-rats/ (accessed 2026-11-11)
- Internet Center for Wildlife Damage Management, “Roof Rat Biology.” icwdm.org/species/rodents/roof-rats/roof-rat-biology/ (accessed 2026-11-11)
- Internet Center for Wildlife Damage Management, “Roof Rat Damage Identification.” icwdm.org/species/rodents/roof-rats/roof-rat-damage-identification/ (accessed 2026-11-11)
- Internet Center for Wildlife Damage Management, “Roof Rat Prevention and Control Methods.” icwdm.org/species/rodents/roof-rats/roof-rat-prevention-and-control-methods/ (accessed 2026-11-11)
- U.S. Centers for Disease Control and Prevention, “Controlling Wild Rodent Infestations.” www.cdc.gov/healthy-pets/rodent-control/index.html (accessed 2026-11-11)
- U.S. Centers for Disease Control and Prevention, “How to Seal Up to Prevent Rodents.” www.cdc.gov/healthy-pets/rodent-control/seal-up.html (accessed 2026-11-11)
- U.S. Centers for Disease Control and Prevention, “How to Trap Up to Remove Rodents.” www.cdc.gov/healthy-pets/rodent-control/trap-up.html (accessed 2026-11-11)
- U.S. Centers for Disease Control and Prevention, “How to Clean Up After Rodents.” www.cdc.gov/healthy-pets/rodent-control/clean-up.html (accessed 2026-11-11)
- U.S. Centers for Disease Control and Prevention, “About Leptospirosis.” www.cdc.gov/leptospirosis/about/index.html (accessed 2026-11-11)
- U.S. Centers for Disease Control and Prevention, “About Rat Bite Fever (RBF).” www.cdc.gov/rat-bite-fever/about/index.html (accessed 2026-11-11)
- U.S. Centers for Disease Control and Prevention, “About Hantavirus.” www.cdc.gov/hantavirus/about/index.html (accessed 2026-11-11)