Rodent Species Identification
Roof Rat: Identification and Behavior
Rattus rattus
A field guide to identifying roof rats, understanding their climbing and nesting behavior, and treating infestations at the roofline where they start.
How to Identify Roof Rat
Roof rats are smaller and sleeker than Norway rats. Adults have a body 6 to 8 inches long and a 6 to 8 inch tail (ICWDM); UC IPM describes the tail as longer than the head and body combined. They weigh 5 to 10 ounces. The body is lean and elongated, the snout is pointed, and the ears are large enough to reach the eyes when gently folded forward.
The fur is usually brown with black intermixed, and the underside may be white, gray or black. ICWDM describes several color forms, including a black form with a gray belly, and says color is a questionable way to tell the subspecies apart.
Droppings are slightly smaller and more pointed than Norway rat droppings, about 1/4 to 1/2 inch long. ICWDM notes they are less often seen on floors, and University of Arizona Extension warns that telling rat species apart from droppings alone is difficult and often misleading.
About 16 inches total (ICWDM); SNHD gives 10 to 14 inches
- Compared to a Norway rat:Smaller and sleeker
- Compared to a house mouse:5 to 10 ounces, against about 1/2 ounce for a house mouse
Distinguishing From Similar Species
- vs Norway Rat: Norway is stockier, heavier, with a shorter tail and smaller ears. Norway rats mostly keep to basements and ground floors, but UC IPM says ceiling-void infestations are not uncommon.
- vs Pack Rat: Roof rats have scaly, mostly hairless tails, while woodrats have furry ones. The two are alike in overall size and shape.
Where Roof Rats Live
Roof rats prefer warm climates and coastal areas, and residential areas with mature landscaping give them good habitat. They often move into citrus groves. UC IPM says the documented range of roof rats is expanding.
Roof rats usually live and nest aboveground. They nest in trees such as palms, in shrubs and ivy, and indoors in attics, walls, false ceilings and cabinets. They may live in trees or attics and climb down to reach food.
Roof rats frequently enter buildings from the roof or from access points near overhead utility lines. They can often be seen at night running along overhead utility lines or fences. Periodically they also burrow into soil and may even occupy sewers.
Roof Rat Behavior
Roof rats are mostly active at night and are agile climbers. They usually begin searching for food shortly after sunset. They may travel 100 to 300 feet for food, and UC IPM notes a roof rat can live in the landscaping of one home and feed on fruit trees at another.
Females generally have 3 to 5 litters a year, with 5 to 8 young per litter. In tropical or semitropical regions the breeding season may be nearly year-round.
Roof rats prefer a wide variety of fruit and nuts but, like Norway rats, are omnivorous. They eat avocados and citrus, often while the fruit is still on the tree, leaving hollowed-out rinds hanging.
Movement is three-dimensional. Florida extension (UF/IFAS) says a roof rat can jump three feet up and more than four feet across. Because roof rats are excellent climbers, openings above ground level must also be sealed.
Damage Roof Rats Cause in Homes
In attics, roof rats tear up insulation for nests and gnaw electrical wiring, and gnawed wiring presents safety concerns, including electrical sparks and fires.
Outdoors, roof rats cause significant losses of tree crops such as citrus and avocados. ICWDM also counts millions of dollars a year in losses of food and feed.
Health Risks From Roof Rats
ICWDM lists murine typhus, leptospirosis, salmonellosis (food poisoning), rat-bite fever and plague among the diseases roof rats can spread. The roof rat has a long history as a carrier of plague, more so than the Norway rat. CDC says southern California, Hawaii and southern Texas report most US cases of flea-borne typhus, although cases likely occur in other states; fleas pick it up from rats, cats or opossums.
For cleanup, CDC says not to vacuum or sweep rodent urine, droppings or nesting materials.
How Roof Rats Enter Homes
ICWDM advises plugging or sealing all openings greater than 1/2 inch and notes that rodent-proofing against roof rats usually takes more time to find entry points. Elevation changes the inspection: soffit corners, gable vents, turbine vents, roof-wall junctions at different roof heights, and any penetration through the roof deck are the priority areas.
Places worth checking include soffit vents, ridge and gable vents, plumbing vent stacks, loose fascia boards, chimney flashing, and the junction where a porch or addition meets the main roof.
UC IPM advises pruning tree limbs within 3 feet of a roof, and roof rats also travel along utility lines and fences. Roof rat exclusion pairs sealing with trimming vegetation.
Roof Rat Control Considerations
Roof rat control starts at the roof. The inspection covers the full roof perimeter, attic interior, soffit system, and adjacent vegetation, and trapping is carried out in the attic along active runways, typically on top of insulation against joists and near roof penetrations.
Exclusion focuses on the roofline. UC IPM advises removing overhanging tree limbs within 3 to 6 feet of the roof and removing climbing plants such as ivy from buildings.
For roof rats, Rat Control calls for an attic inspection, sealing at the roof line, and sometimes reducing tree contact with the roof.
Call to get a trusted local pro out for roof rat control.
Find Service Near YouWhere Roof Rats Are Found
Roof rats prefer warm climates and coastal areas. ICWDM places them along the lower half of the East Coast, throughout the Gulf States upward into Arkansas, all along the Pacific Coast and on the Hawaiian Islands.
University of Arizona Extension says roof rats are well established in some Arizona neighborhoods, and the Mammals of Texas account calls the black rat common over most of Texas, especially in towns. Southern Nevada Health District has documented roof rats in the Las Vegas valley from 1990 onward, and UT Extension reports them becoming more common in Shelby County, Tennessee. In Virginia, extension sources name the roof rat as one of the two main pest rats but much less common there than the Norway rat.
Signs You Have a Roof Rat Problem
Small pointed droppings in attics
Roof rat droppings are about 1/4 to 1/2 inch long with pointed ends, and they are less often seen on floors than Norway rat droppings.
Scratching and scurrying in the attic after dark
Sounds in the attic at night are often the first sign of roof rats.
Hollowed fruit on or under backyard trees
Oranges may be hollowed out while still hanging on the tree, leaving the rind, and lemons may have only the rind eaten.
Smudge marks along travel routes
Smudge marks, from oil and dirt rubbing off the fur, show where rats travel repeatedly. ICWDM says that in food-storage facilities they may be the most prominent sign.
Damaged insulation and nesting material in the attic
Roof rats tear up attic insulation to build nests.
Similar Species and Commonly Confused Rodents
Common Questions About Roof Rats
Look at the tail. If the tail is longer than the head and body, it is a roof rat. If it is shorter, it is a Norway rat. Body shape confirms: roof rats are slim with pointed snouts and large ears, Norway rats are stocky with blunt snouts and small ears. Location helps too: roof rats usually live and nest aboveground, while Norway rats usually keep to lower floors and basements.
Sources and Further Reading
Sources for roof rat facts on this page:
- Pest Notes: Rats (UC Statewide IPM Program (UC IPM))
- Roof Rats (Internet Center for Wildlife Damage Management (ICWDM))
- Roof Rat Biology (Internet Center for Wildlife Damage Management (ICWDM))
- Roof Rat Damage Identification (Internet Center for Wildlife Damage Management (ICWDM))
- Roof Rat Prevention and Control Methods (Internet Center for Wildlife Damage Management (ICWDM))
- How to Identify and Discourage Roof Rats (University of Arizona Cooperative Extension)
- AZ1280: Roof Rat Control around Homes and Other Structures (University of Arizona Cooperative Extension)
- Black Rat (The Mammals of Texas, online edition) (Natural Science Research Laboratory, Texas Tech University)
- Rodent Pests (Southern Nevada Health District)
- Old World Rats (Washington Department of Fish and Wildlife (WDFW))
- Landscaping Methods to Prevent Pests from Entering Your Home (IN1397) (UF/IFAS Extension)
- PB1303: Managing Pests Around the Home (University of Tennessee Institute of Agriculture, UT Extension)
- Schools Integrated Pest Management (IPM) for Rats and Mice (Virginia Tech Department of Entomology, School IPM program)
- Mammals in Virginia (465-314) (Virginia Cooperative Extension, Virginia Tech)
- Rodent Control (Florida Department of Health in Gadsden County)
- How to Clean Up After Rodents (Centers for Disease Control and Prevention (CDC))
- About Flea-borne Typhus (Centers for Disease Control and Prevention (CDC))
- About Rat-bite Fever (Centers for Disease Control and Prevention (CDC))
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