Adults with combined head and body length 6-8 inches and the tail length is between 7-10 inches. The fur is soft and smooth; color is between brown with black intermixed to gray to black above with underside white, gray, or black. The muzzle pointed, eyes and ears are large, and they are almost naked. The tail will be scaly, uniformly dark, longer than head and body combined.
Roof rats are primarily nocturnal and they are very cautious. Although they constantly explore their surroundings, they shy away from new objects and changes. They prefer to nest in the upper parts of structures but may be found under buildings as well as in basements and sewers. Outdoors, they prefer to nest in higher places such as in trees but may be found in burrows in or under vegetation around the structure. These are social animals, but less than Norway rats. Several nests can be located within a given area. An opening of greater than a 1/2 inch is required for entry into buildings.
They will eat almost anything, but prefer fruits, vegetables and cereals. If the eaten food material proves to be distasteful, they are quick to develop food/bait shyness. Once they find an acceptable/preferred food, rats tend to eat their fill at one sitting and will return time after time.
Once established indoors, roof rats tend to follow the same route or pathway between their nest and food sources. Runways along vertical surfaces will usually include dark rub or swing marks on the vertical surface where their fur makes contact. Their runways will be free of debris, outdoors, the grass will be worn away to the bare soil.
Roof rats reach sexual maturity in 2-5 months. Pregnancy lasts an average of 22 days. The young are blind and naked at birth, with hair appearing in about seven days and their eyes opening in 12-14 days. They are weaned at about 3-4 weeks. The average number of litters is 4-6 per year, each containing an average of 6-8 young. Adults on an average live 9-12 months.
Roof rats have poor vision and are color blind, but their other senses are of keen development. Touch is done with their whiskers. They are good runners, excellent climbers and jumpers and if forced, rather good swimmers.
A roof rat requires 1/2-1 oz. of food and 1 oz. of water each day, with the water often coming from its food.
Rattus rattus Linnaeus