Brown Rats

The Norway rat, also called the brown rat, probably originated in eastern Asia, possibly northern China. The first record of its appearance in Europe was 1553, and it is now found throughout the world. It is usually grayish brown above and pale gray or brown on its underparts, but blackish varieties also occur. Norway rats breed throughout the year. Gestation varies from 21 to 24 days, and litter size is usually between 6 and 12 young.