Order and Family:
Muridae, Mice and Rats
Brownish or grayish above; underparts grayish to whitish, but not white. Scaly, sparsely haired tail uniformly dark; longer than half total length. Prominent ears. L 12 3/4–17 7/8″ (325–455 mm); T 6 3/8″–10 1/8″ (160–255 mm); HF 1 1/8–1 5/8″ (30–40 mm); E 5/8–1″ (17–27 mm); Wt 4–12 3/8 oz (115–350 g).
Norway Rat has tail proportionally shorter (less than half total length). Rice rats have tail darker above than below. Woodrats have white underparts.
Breeds year-round; several litters per year, each of 2–8 young; gestation 21–26 days.
Mainly around seaports and buildings; sometimes in natural habitats.
Southern and coastal U.S.; inland in West, as far north as w Nevada; east of Rockies to e Arkansas, w Kentucky, n Alabama, n Georgia, and most of North Carolina and Virginia. Most abundant in South, along Atlantic Coast north to e Maine, and along Pacific Coast to extreme sw British Columbia.
The Black Rat occurs in a great many varieties and races, or subspecies, of which few are actually black, despite the common name. Believed to have come from Southeast Asia, this species spread through Europe centuries ago, long before the arrival of the Norway Rat. It appeared in Central and South America in the mid-16th century, evidently carried there aboard Spanish ships; it arrived in North America with the early colonists at Jamestown in 1609, and gradually spread across the continent. Formerly much more common, it has often been displaced by the slightly larger and more aggressive Norway Rat; this may be because the Black Rat does better in tropical climates and the Norway Rat in temperate climates, rather than because of overt competition. As Black Rats are far more common than Norway Rats on ships, they continue to be reintroduced at seaports. Excellent climbers, in the South they live in the upper stories of buildings; they also make nests in tangled vines and in trees. Omnivorous but partial to grain, the Black Rat does enormous damage in docks and warehouses, contaminating with its droppings what it does not eat. Like other rats, it carries a number of diseases, including bubonic plague, which is transmitted by its fleas. Snakes, owls, dogs, and cats are its chief predators.