Brown Rat

The brown rat is a large, widespread and common rat that lives wherever humans do, particularly in towns and cities. It is brown or dark grey above and lighter below, with a tail shorter than the head and body. Adults weigh 140 to 500 g, though breeding wild animals are often under 300 g, and a pup weighs about 6 g at birth (Wikipedia, general species account).

It is nocturnal, a good swimmer both on the surface and underwater, and digs extensive burrow systems. It is a true omnivore that eats almost anything, though cereals make up a substantial part of the diet. Young pups use different ultrasonic cries to direct their mother's search in the nest (Wikipedia, general species account).