Orange County Health Department >Environmental Health >Rodent Control >Rodents >Rats >Sewer Rats

As an adult the Norway Rat can weigh between 12-16 oz. with a body length of 6-8 inches long. The nose is blunt with small ears, and small eyes. The fur is shaggy and coarse with variation in colors. The tail is shorter than the head and body combined, and scaly.
Norway rats live in close association with people. They burrow to make nests under buildings and other structures, beneath concrete slabs, along stream banks, around ponds, in garbage dumps, and at other locations where suitable food, water, and shelter are present.
In urban or suburban areas they live in and around residences, in cellars, warehouses, stores, slaughterhouses, docks, and in sewers. Although they can climb, Norway rats tend to inhabit the lower floors of multi-story buildings.
Norway rats are primarily nocturnal. They usually become active about dusk, when they begin to seek food and water. Some individuals may be active during daylight hours when the rat population is high, when disturbed (weather change, construction, etc.) or when their food source is threatened.