The roof rat (Rattus Rattus) is one of two introduced rats found in the contiguous 48 states. The Norway rat is the other species and is better known because of its widespread distribution. When distinguishing the Norway rat from the Roof rat, pull the tail back over the body. The tail of the Roof rat will reach the nose. The tail of the Norway rat will not reach beyond the ears.
- A third rat species, the Polynesian rat, is present in the Hawaiian Islands but not on the mainland.
- Rattus Rattus is commonly known as the roof rat, black rat or ship rat. Roof rats were common on early sailing ships and apparently arrived in this country by that route. This rat has a long record as a carrier of plague.
- Roof rats range along the lower half of the East Coast and throughout the Gulf States and upward into Arkansas. They also exist along the Pacific Coast and are found on the Hawaiian Islands. The roof rat is apparently not quite as adaptable as the Norway rat, which is one reason it has not spread throughout the country. Its geographic distribution suggests it is more suited to tropical and semi-tropical climates. Occasionally isolated populations are reported from areas not within their normal distribution range; however, these instances are rare. Most of the Great Plains states are free of roof rats but infestations can occur.
- Roof rats are more aerial than Norway rats in their habitat selection and often will live in trees or on vine covered fences. Landscaped residential or industrial areas provide good habitat, as does vegetation of riverbanks and streams. They will often move into sugarcane and citrus groves. Roof rats are sometimes found living in or around poultry or other farm buildings as well as in industrial sites where food and shelter are available. Being agile climbers, Roof rats frequently enter buildings from the roof or accesses near utility lines which they use to travel from area to area. They have been found in sewer systems, but this is not very common.
- Born in a nest about 21 to 23 days after conception, the young rats are naked and their eyes are closed. The 5 to 8 young in the litter develop rapidly, growing hair within a week. When they are 9 to 14 days old, their eyes open and they begin to explore for food and move about near their nest. In the third week they begin to take solid food. The number of litters depends on the area and varies with nearness to the limit of their climatic range, availability of nutritious food, density of the local rat population and age of the rat. The young may continue to nurse until 4 or 5 weeks old. Young rats generally cannot be trapped until about 1 month old. At about 3 months of age they are completely independent of the mother and are reproductively mature. In tropical or semitropical regions, the breeding season may be nearly year-round. Usually the peaks in breeding occur in the spring and fall.