Where Do Rats Naturally Live?

Rats are not native to the Pacific Northwest, and they have been introduced into the region by shipping cargo or stowing away on cars and trains. The rats have excellent swimming abilities, and they may have reached their current location by swimming through a river. During the 17th century, large groups of rats swam across the Volga River in Russia. They can swim up to half a mile and can survive for up to three days on water.

Rat social systems are complex, and they can change based on population density and other factors, including density of resources and predation levels. Lott (1984) discusses variations in vertebrate social systems, and he cites the example of the low-density rat population. In high-density populations, multiple males mate with many females, using a group mating system. During high-density populations, breeding behavior of rats is noncompetitive, and males may mate with as many as ten to twenty females at once.

Rats are nocturnal and crepuscular, which means they are active at night and during twilight. They live in groups of one to six and have their own nest chamber. Males and females often share burrows and raise young together. The young will then disperse when they are weaned.