The Norway rat belongs to a diverse contrasting group of brown rats. Despite their name, this species is native to northern China. They were initially commonly found in forests but became domesticated as companion species with humans.

Brown rats (Rodents) are the most significant members of their rodent family. They reach an average length of 16.4 inches (40 cm), with a tail that is a little shorter than their entire body. 

They generally weigh 0.5 to just under 1 pound (200 to 500 grams), and males are usually larger than females.

Their medium-length, dense fur covers their bodies, except for the nose, ears, and tail, which are entirely bald. Their natural colors range from gray to brown, often with lighter hues on the underside. 

They use different means of communication, like vocalizing and visual signals.

Brown rats are hunters and can eat a wide range of foods, and this characteristic has helped it spread worldwide. One study on the rat’s bowel content found over 4,000 items in their stomach.