Roof Rat Biology

Roof Rats are also known as black rat, ship rat, or Rattus rattus Linnaeus.


A roof rat (black rat, ship rat) adult head and body length is 6-8 inches (16-20 centimeters); tail length is 7-10 inches (19-25 centimeters); weight is about 5-9 ounces, up to 12 ounces.
Roof Rat


Soft, smooth fur; pointed muzzle; large eyes; large, almost naked ears, which can be pulled over the eyes. Scaly, dark tail is longer than combined head and body length.


Brown with black mixed in, to gray, to black on top with white; gray or black underside.


Adult droppings are up to a half inch (12.5 millimeters) long, and are spindle shaped with pointed ends.

Where Found

They are probably from southeast Asia, but now found around the world. In the U.S., Rattus rattus is most common in coastal and southern states, especially near seaports.


Outdoors roof rats nest in high places such as trees, but sometimes in burrows under plants. Indoors they nest in high places in structures, but sometimes in basements, sewers, or under buildings.


Roof rats eat almost anything, but they prefer fruit, vegetables, and cereal products. They get their water often from their food. They eat a lot at one time, and will return to that place time after time. If they do not like a food or bait they quickly become shy of it.


Roof rats mature in 2-5 months, and are adults for 9-12 months. Pregnancy takes 3 weeks. Newborns get hair after 1 week, open eyes after about 2 weeks, and are weaned at 3-4 weeks. Female has 4-6 litters per year, with 6-8 young per litter. They have keen hearing, smell, taste and touch (long whiskers), but bad vision, and are colorblind. They are good at running, climbing, jumping, and even swimming. They are nocturnal and explore a lot, but are cautious and shy away from new objects.


Roof rats gnaw, eat stored food, and transmit disease by droppings and urine, bites, and the fleas and mites in their fur.


An opening larger than a half inch (12 millimeters) allows entry of roof rats into buildings.