A Squirrel belong to family Sciuridae of small or medium-size rodents. Squirrels are indigenous to the Americas, Eurasia, and Africa, and have been introduced to Australia. The earliest known squirrels date from the Eocene and are most closely related to the mountain beaver and to the dormouse among living rodent families.
Squirrels are generally small animals, ranging in size from the African pygmy squirrel at 7–10 cm (2.8–3.9 in) in length and just 10 g (0.35 oz) in weight, to the Alpine marmot, which is 53–73 cm (21–29 in) long and weighs from 5 to 8 kg (11 to 18 lb). Squirrels typically have slender bodies with bushy tails and large eyes. In general, their fur is soft and silky, although much thicker in some species than others. The color of squirrels is highly variable between—and often even within—species.
Squirrels are generally inquisitive and persistent animals. In residential neighborhoods, they are notorious for tenaciously trying to circumvent obstacles in order to eat from bird feeders. Although they are expert climbers, and primarily arboreal, some species of squirrels also thrive in urban environments, where they have adapted to humans.