A mouse is a mammal that belongs to one of numerous species of small rodents. The best known mouse species is the common house mouse. It is found in nearly all countries and, as the laboratory mouse, serves as an important model organism in biology; it is also a popular pet. The American white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus) also sometimes live in houses. These species of mice live commensally with humans. Although they may live up to two years in the lab, the average mouse in the wild lives only about 3 months, primarily due to heavy predation. Cats, wild dogs, foxes, birds-of-prey, snakes and even certain kinds of insects have been known to prey heavily upon mice. Nevertheless, due to its incredible adaptability to almost any environment, and its ability to live commensally to humans, it is regarded to be the second most successful mammalian species living on earth today, after the rat. Mice can be harmful pests, damaging and eating crops and spreading diseases through their parasites and feces. The original motivation for the domestication of cats is thought to have been for their predation of mice and their relatives, the rats.