What Is a Roof Rat?

"Roof rat" is one of many common names for the black rat, Rattus rattus. This species has the dubious fame of being the one that spread bubonic plague throughout Europe in the Middle Ages. The black rat has since been overtaken by the brown rat, Rattus norvegicus, as the most common rat in residential areas of Europe and North America, with a couple of notable exceptions including Florida. Black rats are still common on farmland. They also remain the dominant species in much of Asia.

Black rats come in a range of colors, primarily -- as the name suggests -- black or very dark brown, but also various shades of brown, gray, beige and white. Black rats have slender bodies, pointed faces and very long, hairless tails. On average, they are a little smaller than brown rats. Black rats average about 6 to 8 inches in length, excluding tail, while brown rats reach about 7 to 10 inches. In both species, males are larger than females, although the females may be more aggressive.

Black rats are climbing rats and semi-arboreal, or partially tree-living, in their natural habitat. They often become a pest on fruit farms, where the only real way to keep them out of the trees is to fit physical barriers around the trunks. Black rats are omnivores that eat practically anything nontoxic, although they seem to prefer plant foods such as fruits and grains to animals such as insects.

These rats are highly social and live in groups consisting of several males and several females. They establish a complex hierarchy and communicate with scent, body language and a range of vocalizations, most of which are inaudible to humans. They reproduce rapidly. A female matures at about 3 months and can then have a litter every two to three months thereafter, with litters of up to 12 pups at a time.

Domestic pet or laboratory rats are nearly always brown rats. Black rats are rarely kept in captivity. Black rat intelligence and adaptability is equal to their cousins. However, because they have not been fully domesticated, you are unlikely to find a black rat to be as peaceful and friendly as a domestic brown rat and they are not recommended as pets. Wild black rats can become serious pests, especially around fruit trees and crops. Removing access to the food supply is the first step to controlling them. Call a pest control company if further action is required. In India, the famous and sacred rats of the Karni Mata temple are black rats. Intriguingly, given the close contact between the thousands of temple rats and visitors to the temple, there have been no outbreaks of diseases linked to the rats.