No murid rodent is native to the Americas, yet house mice live everywhere
The murid family of mice, rats and gerbils holds around 870 species, making it the largest or second-largest mammal family. None evolved in the Americas, but the house mouse and black rat rode along with human travellers and now live nearly worldwide, one of the great hitchhiking stories in biology.
The name comes from the Latin mus, mouse, since all true mice belong to the family. Murids occur naturally across Eurasia, Africa and Australia, in habitats from tropical forest to tundra, though not in Antarctica or on many ocean islands. Most live on the ground, but some burrow, climb or swim. Gerbils in particular cope with deserts and can go a long time with very little water.
Body plans vary around a common theme: a slender body about ten centimetres long, a scaly tail longer than the body, a pointed snout and prominent whiskers, usually in some shade of brown. The extremes run from the African pygmy mouse, 4.5 to 8 centimetres, to the northern Luzon giant cloud rat at 50 centimetres. Some hop on long feet; others climb with broad feet and gripping tails. All lack canines and premolars, gnawing instead with incisors that grow for life.
Diets range from plants and mixed fare to strict specialists that eat only earthworms, particular fungi or aquatic insects, and many species store seeds for winter. Hearing and smell are excellent. Some species are highly social and others solitary.
Their success comes from speed of reproduction. Pregnancy usually lasts twenty to forty days, females may have several large litters a year, and in warm regions breeding can continue all year. Young are generally born blind and hairless, though spiny mice are an exception. Most live less than two years, and populations often boom and crash on a three- to four-year cycle as food runs out. Few fossils survive, but murids probably arose from hamster-like ancestors in tropical Asia in the early Miocene before spreading into cooler climates.
Source: Muridae
