Rodents have adapted to most habitats and include terrestrial, fossorial, saltatorial, arboreal, gliding, and semiaquatic forms. They range in size from the smallest mice, weighing only a few grams, up to the largest living rodent, the capybara, weighing up to 50 kilograms. Most rodents are primarily omnivorous, feeding on bark, grass, seeds, other vegetation, insects and other animal matter. With a few exceptions, an external tail is present, but its form and length vary greatly.
Rodents are well haired over most of their body.
Most are quadrupedal, but some arid-land species have greatly enlarged hind limbs, and are capable of ricochetal locomotion. The distribution of rodents is almost worldwide. They are native to most land areas except some Arctic and oceanic islands, New Zealand and Antarctica.