Rodents (from Latin rodere, “to gnaw”) are mammals of the order Rodentia, which are characterized by a single pair of unremittingly growing incisors in each of the upper and lower jaws. About forty percent of all mammal species are rodents; they are found in vast numbers on all continents except Antarctica. They are the most diversified mammalian order and live in a variety of terrestrial habitats, including human-made environments. There are species that are arboreal, fossorial (burrowing), and semi-aquatic. Well-known rodents include mice, rats, squirrels, prairie dogs, porcupines, beavers, guinea pigs, hamsters, and capybaras. Other animals such as rabbits, hares and pikaswere once included with them, but are now considered to be in a separate order, Lagomorpha.
Most rodents are small animals with robust bodies, short limbs and long tails. They use their sharp incisors to gnaw food, excavate burrows and defend themselves. Most eat seeds or other plant material, but some have more varied diets. They tend to be social animals and many species live in societies with complex ways of communicating with each other. Mating among rodents can vary from monogamy, to polygyny, to promiscuity. Many have litters of underdeveloped, altricial young, while others have precocial young that are relatively well developed at birth.
The rodent fossil record dates back to the Paleocene on the supercontinent of Laurasia. They greatly diversified in the Eocene, as they spread across continents, sometimes even finding means to cross oceans. Rodents reached both South America and Madagascar from Africa, and were the only terrestrial placental mammals to reach and colonize Australia.
Rodents have been used as food, for clothing, as pets and as laboratory animals in research. Some species, in particular the brown rat, the black rat, and the house mouse are serious pests, eating and spoiling food stored by humans, and spreading diseases. Accidentally introduced species of rodents are often considered to be invasive, as they sometimes threaten the survival of native species, such as island birds, previously isolated from land-based predators.
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. “True rats” are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus. Many members of other rodent genera and families are also referred to as rats, and share many characteristics with true rats.
Rats are typically distinguished from mice by their size. Generally, when someone discovers a large muroid rodent, its common name includes the term rat, while if it is smaller, the name includes the term mouse. The muroid family is broad and complex, and the common terms rat and mouse are not taxonomically specific. Scientifically, the terms are not confined to members of the Rattus and Mus genera, for example, the pack rat and cotton mouse.
A mouse (plural: mice) is a small mammal belonging to the order of rodents, characteristically having a pointed snout, small rounded ears, a body-length scaly tail and a high breeding rate. The best known mouse species is the common house mouse (Mus musculus). It is also a popular pet. In some places, certain kinds of field mice are also common. They are known to invade homes for food and occasionally shelter.
The American white-footed mouse (Peromyscus leucopus) and the deer mouse (Peromyscus maniculatus), as well as other common species of mouse-like rodents around the world, also sometimes live in houses. These, however, are in other genera.
Cats, wild dogs, foxes, birds of prey, snakes and even certain kinds of arthropods have been known to prey heavily upon mice. Nevertheless, because of its remarkable adaptability to almost any environment, the mouse is one of the most successful mammalian genera living on Earth today.
Mice can at times be vermin, damaging and eating crops, causing structural damage and spreading diseases through their parasites and feces. In North America, breathing dust that has come in contact with mouse excrement has been linked to hantavirus, which may lead to Hantavirus Pulmonary Syndrome (HPS).
Primarily nocturnal animals, mice compensate for their poor eyesight with a keen sense of hearing, and rely especially on their sense of smell to locate food and avoid predators.
Mice build intricate burrows in the wild. These burrows typically have long entrances and are equipped with escape tunnels/routes. In at least one species, the architectural design of a burrow is a genetic trait.