General Characteristics

    Squirrels must count as the most familiar animals. The family name means “shade-tail” from the habit of lying sprawled on a horizontal limb with tail held over his back as a sunshade. Every continent except Australia and Antarctica is home to a rich array of squirrels. Squirrels are often active in daylight, they frequently live in large colonies and are tolerant of humans. Squirrels have very generalized features that have enabled them to spread into a wide variety of habitats and to develop numerous species.  Typically squirrels have a long, cylindrical body with a short or long bushy tail. Most squirrels have fine soft hair and in some species the coat is very thick and valued by man as fur. Many species molt twice a year to adapt to the environment. Male, female and young are similar in appearance but even within species there can be considerable variation in colour as for instance in the variable squirrels of Thailand where some populations are pure white, others pure black or red and yet others a combination of different colours.

    They first appeared about 30 million years ago in North America but soon spread in the Old World and then in Africa and Southeast Asia. Squirrels population densities vary according to the species, habitat and number of species present. Factors that limit the density of day-active squirrels are the spacing and timing of available food and competition for these sources. The main natural predators of squirrels’ population are carnivores such as weasels, foxes, coyotes, martens and birds like hawks and owls.   

    There are two basic groups of squirrels: ground squirrels, tree squirrels.

Ground squirrels: 

    Distribution: ground-dwelling squirrels are widely distributed throughout much of the world. They are absent from most of South America and Australia.

    There are a number of sub-species of ground squirrels such as Mexican ground squirrels, Mohave ground squirrels and Richardson’s ground squirrels. As an example we consider the Richardson’s ground squirrels.

    Agricultural practices on the short-grass prairies of Canada have placed humans in conflict with this squirrel. In fact this species is one of the least liked squirrels for following reasons. Richardson’s squirrel tends to consumes large quantities of grain and it has been known to play host to the tick which carries Rocky Mountain fever, to fleas which cause bubonic plague and to bacillus which causes tularemia. When not harassed by humans, it becomes accustomed to people and an entertaining guest in picnic grounds. This species is hibernator and spends a large amount of its lifetime underground. The active season last about 7-8 months, from March to September but the squirrels are aboveground for only a portion of this period. Each animal hibernates alone. The hibernaculum is filled with dry grass, which serves as an insulation. When in hibernation these squirrels are safe from all predators except badgers, which use their excavating skills to dig down 50-100 cm to the hibernaculum. The Richardson’s squirrel has adapted to several types of habitats, but those best suited to its needs are open, rolling prairie hills where burrows can be readily made in dry sand or gravel. This squirrel likes to have a clear view of its surroundings so that should danger threaten it can quickly disappear in its burrow; the entrance to it is seldom more than a few feet away. The Richardson’s ground squirrel was named after Sir John Richardson, a surgeon-naturalist who was a member of Sir John Franklin’s first two expeditions into the Arctic.

Tree squirrels: 

    Distribution: in the Americas, tree squirrels range from the northern tree line to northern Argentina. In Europe, they occur across Europe, parts of Middle East, across Siberia and in China, Japan and southeast Asia. African species occur across most of the continent south of the Sahara.

    Easter Grey squirrels (Sciurus carolinensis) are among the most known sub-species of squirrels. While most other rodents run across the ground searching for food, these squirrels became adapted for climbing and found a new niche, and quickly made it their own. In shape and habits, these squirrels are very distinctive. All have lithe, cylindrical flexible bodies and strong limbs, and most have long bushy tails aids to climbing and balancing. Long toes equipped with sharp claws enable them to grip bark so firmly that, with their hind feet flexed backwards, they can held themselves head-down even on vertical trunks. Grey squirrels have excellent senses of hearing and smell and a finely tuned sense of touch aided by sensitive whiskers not only on their cheeks, but also on their legs and feet. But it is perhaps their eyesight that is most remarkable. There are also among the few mammals that possess good colour vision. Average measurement of adults: length 478 (430-500) mm, tail 235(210-240)mm, hind foot 68 (60-70)mm, ear 30 mm  and weight of males 526 g and of female 520 g.

    Grey squirrels are grey above and on their flanks and white below. The black phase of the Grey squirrel is commonly seen in the colder areas, most likely due to the more efficient thermoregulation of black colour. The Grey squirrel is a socially tolerant species. Often several adults may feed in close proximity, or occupy the same den. Only the female show decided territoriality and drive intruders away from the den tree. There is a definite dominance hierarchy in Grey squirrels including both males and females. The social hierarchy is decided in battles during brief encounters when the squirrels sidle up to each other. Animals of low status are often forced to range widely and emigrate at times of food shortage. These animals taking part in migrations are often the young of the year.  

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Conservation I Personal Observations I Pictures I Sounds of the Squirrel I References I Sites of Interest