Norway Rat: Also known as the Brown Rat, this is the giant rat you hear about living in New York City sewers. It can grow to twice the size of the Roof Rat. The Norway Rat is different from the Roof Rat in several ways. Norway Rats have a thicker, heavier body, and a shorter tail. They have a more blunt snout. They are usually more brown in color than the Roof Rats. They prefer to live at ground level, hence their presence in the sewers. They seem to be highly dependent upon people for food and shelter sources. Like all rats, they have poor vision, and rely primarily upon their sense of smell and their highly specialized senses of feel and balance to survive. As with all rodents, their teeth grow continuously, and thus they gnaw on many surfaces to wear down their teeth.