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Rodents

Black Rat

  • Description:13-18 inches nose to tail tip. Blunt snout, fur is generally reddish brown to gray. Large and robust. It is the dominant rat in Europe and much of North America making it the most successful mammal on the planet after humans.

  • Breeding: The brown rat can breed throughout the year if conditions are suitable, a female producing up to five litters a year. The gestation period is only 21 days and litters can number up to fourteen, although seven is common.

  • Habitat: In the absence of humans, brown rats prefer damp environments such as river banks. However, the great majority are now linked to man-made environments, such as sewage systems. In New York City there is great debate over the size of the rat population with estimates from almost 100 million rats to as few as 250,000.

  • Brown rats have acute

    hearing, are sensitive to ultrasound, and possess a very highly developed olfactory sense.

  • The brown rat is nocturnal and is a good swimmer, both on the surface and underwater, but unlike the related black rat it is a poor climber. Brown rats dig well, and often excavate extensive burrow systems

Brown Rat

Description: Brownish or grayish above; underparts grayish to whitish, but not white. Scaly, sparsely haired tail uniformly dark; longer than half total length. Prominent ears.

  • Similar Species Norway Rat has tail proportionally shorter (less than half total length).

  • Breeding Breeds year-round; several litters per year, each of 2–8 young; gestation 21–26 days.

  • Sign Similar to sign of Norway Rat.

  • Habitat Mainly around seaports and buildings; sometimes in natural habitats.

  • 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.

House Mouse

Description: Grayish brown above; nearly as dark below. Tail dusky above and below; nearly hairless. Ungrooved incisors. L 5 1/8–7 3/4″ (130–198 mm); T 2 1/2–4″ (63–102 mm); HF 1/2–7/8″ (14–21 mm); E 3/8″– 3/4″ (11–18 mm); Wt 5/8–3/4 oz (18–23 g).

  • Similar Species: Deer mice (Peromyscus species) have white underparts. Harvest mice have grooved incisors.

  • Breeding: Gestation 18–21 days; several litters per year, each of 3–16 young; reproduces spring through fall in North, year-round in South.

  • Habitat: Buildings; areas with good ground cover, especially cultivated fields. Uncommon in undisturbed or natural habitats.

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