The Roof Rat has smooth black or brown fur and is rather large (at maturity), measuring from 7 to 10 inches long, with a long tail, pointed snout and large ears and eyes. Roof Rats are nimble climbers and can wriggle through holes and openings as small as 1/2 inch wide.
Creating nests inside and under buildings, and in piles of refuse or old wood, though, as their name suggests, they often are found higher up in structures. Roof Rats are omnivorous, but prefer variety in their diet, seeking out grains, vegetables, fruits and nuts.
The Roof Rat can reproduce at the age of four months and will product 4 to 6 litters per year with up to 8 young per litter. Roof Rats typically live up to one year and often are carriers of serious diseases.
Probably the most easily recognized characteristic that differentiates the roof rat from native rats is the tail. Roof rat tails are hairless, scaly, and longer than the combined length of their head and body, whereas the tails of pack rats are hairy, have less apparent scales and are shorter than their head and body. (Factoid Source: University of Arizona Cooperative Extension)