Cute Squirrel Pictures Biography
Squirrels belong to a large family of small or medium-sized rodents called the Sciuridae. The family includes tree squirrels, ground squirrels, chipmunks, marmots (including woodchucks), flying squirrels, and prairie dogs. 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.The word "squirrel", first specified in 1327, comes from Anglo-Norman esquirel from the Old French escurel, the reflex of a Latin word sciurus. This Latin word was borrowed from the Ancient Greek word σκίουρος, skiouros, which means shadow-tailed, referring to the bushy appendage possessed by many of its members.
The native Old English word, ācweorna, survived only into Middle English (as aquerne) before being replaced. The Old English word is of Common Germanic origin, with cognates such as German Eichhorn, Norwegian ekorn, Dutch eekhoorn, Swedish ekorre and Danish egern.
Skull of an Oriental giant squirrel (genus Ratufa) - note the classic sciuromorphous shape of the anterior zygomatic region.
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. Their fur is generally soft and silky, although much thicker in some species than others. The color of squirrels is highly variable between—and often even within—species.
The hind limbs are generally longer than the fore limbs, and they have four or five toes on each foot. Their paws on their fore feet include a thumb, although this is often poorly developed. The feet also have soft pads on the undersides.
Squirrels live in almost every habitat from tropical rainforest to semiarid desert, avoiding only the high polar regions and the driest of deserts. They are predominantly herbivorous, subsisting on seeds and nuts, but many will eat insects and even small vertebrates.
As their large eyes indicate, squirrels generally have an excellent sense of vision, which is especially important for tree-dwelling species. They also have very versatile and sturdy claws for grasping and climbing. Many also have a good sense of touch, with vibrissae on their heads and limbs.
The teeth of sciurids follow the typical rodent pattern, with large gnawing incisors that grow throughout life, and grinding cheek teeth set back behind a wide gap, or diastema. The typical dental formula for sciurids is 
The life span of the Gray squirrel is approximately six years. Most urban squirrels do not reach their first birthday. This is due not to predators, but rather to automobiles. Compare this to its rural counterpart, which often perishes from lack of food.
Several species of squirrels have melanistic phases. In large parts of United States and Canada, the most common variety seen in urban areas is the melanistic form of the eastern gray squirrel.
Squirrels breed once or twice a year and give birth to a varying number of young after three to six weeks, depending on species. The young are born naked, toothless, and blind. In most species of squirrel, only the female looks after the young, which are weaned at around six to ten weeks of age and become sexually mature at the end of their first year. Ground-dwelling species are generally social animals, often living in well-developed colonies, but the tree-dwelling species are more solitary.
Ground and tree squirrels are typically diurnal or crepuscular, while flying squirrels tend to be nocturnal—except for lactating flying squirrels and their offspring, which have a period of diurnality during the summer.[
Squirrel eating a peanut
The Indian palm squirrel is the most common type of squirrel found in India.
Squirrels cannot digest cellulose, so must rely on foods rich in protein, carbohydrates, and fats. In temperate regions, early spring is the hardest time of year for squirrels, because 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' diets consist primarily of a wide variety of plants, 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, young snakes and smaller rodents. Indeed, some tropical species have shifted almost entirely to a diet of insects.
Predatory behavior has been noted by various species of ground squirrels, particularly the thirteen-lined ground squirrel. For example, Bailey, a scientist in the 1920s, observed a thirteen-lined ground squirrel preying upon a young chicken. Wistrand reported seeing this same species eating a freshly killed snake. Whitaker examined the stomachs of 139 thirteen-lined ground squirrels and found bird flesh in four of the specimens and the remains of a short-tailed shrew in one; Bradley, examining white-tailed antelope squirrels' stomachs, found at least 10% of his 609 specimens' stomachs contained some type of vertebrate, mostly lizards and rodents. Morgart observed a white-tailed antelope squirrel capturing and eating a silky pocket mouse