this: the animal

right|thumb|A Red Squirrel with pronounced winter ear tufts A squirrel is one of many small or medium-sized rodents in the family Sciuridae. In the English-speaking world, squirrel commonly refers to members of this family's genera Sciurus and Tamiasciurus, which are tree squirrels with large bushy tails, indigenous to Asia, the Americas and Europe. Similar genera are found in Africa. The Sciuridae family also include flying squirrels, as well as ground squirrels such as the chipmunks, prairie dogs, and woodchucks. Members of the family Anomaluridae are sometimes misleadingly referred to as "scaly-tailed flying squirrels" although they are not closely related to the true squirrels.

In USA and Canada common squirrels include the Fox Squirrel (S. niger); the Western Gray Squirrel (S. griseus); the Douglas Squirrel (Tamiasciurus douglasii); the American Red Squirrel T. hudsonicus; and the Eastern Grey Squirrel (S. carolinensis), of which the "Black Squirrel" is a variant. In Europe the Red Squirrel or Eurasian red squirrel (Sciurus vulgaris) is the most common native species, although the Eastern Grey Squirrel (S. carolinensis) has been introduced in some countries and has displaced the red in many areas including most of Britain.

Etymology

The word squirrel, first attested in 1327, comes via Anglo-Norman esquirel from the Old French escurel, the reflex of a Latin word sciurus which was itself borrowed from Greek. The word itself comes from the Greek word σκιουρος, skiouros, which means shadow-tailed, because they use their tail to shade their whole body.

The native Old English word, ācweorna, only survived into Middle English (as aquerna) before being replaced. The Old English word is of Common Germanic origin, with cognates such as German Eichhorn/Eichhörnchen and Norwegian ekorn.

Diet

Unlike rabbits or deer, squirrels cannot digest cellulose and must rely on foods rich in protein, carbohydrates, and fat. In temperate regions early spring is the hardest time of year for squirrels, since buried nuts begin to sprout and are no longer available for the squirrel to eat, and new food sources have not become available yet. During these times squirrels rely heavily on the buds of trees. Squirrels' diet consists primarily of a wide variety of plant food, including nuts, seeds, conifer cones, fruits, fungi and green vegetation. However some squirrels also consume meat, especially when faced with hunger. Squirrels have been known to eat insects, eggs, small birds, snakes and rodents.

Ground and tree squirrels are typically diurnal, while flying squirrels tend to be nocturnal – except for lactating flying squirrels and their offspring, which have a period of diurnality during the summer.