Squirrels презентация

Squirrel

Squirrels are members of the family Sciuridae, a family that includes small or medium-size rodents. The squirrel family includes tree squirrels, ground squirrels, chipmunks, marmots (including groundhogs), flying squirrels, and prairie dogs amongst other rodents. Squirrels are indigenous to the Americas, Eurasia, and Africa, and were introduced by humans to Australia. The earliest known fossilized squirrels date from the Eocene epoch, and among other living rodent families, the squirrels are most closely related to the mountain beaver and to the dormice.
Squirrels are generally small animals, ranging in size from the African pygmy squirrel and least pygmy squirrel at 10–14 cm in total length and just 12–26 g in weight, to the Bhutan giant flying squirrel at up to 1.27 m in total length, and several marmot species, which can weigh 8 kg or more. Squirrels typically have slender bodies with very long very bushy tails and large eyes. In general, their fur is soft and silky, though much thicker in some species than others. The coat color of squirrels is highly variable between—and often even within—species.
In most squirrel species, the hind limbs are longer than the fore limbs, while all species have either four or five toes on each paw. The paws, which include an often poorly developed thumb, have soft pads on the undersides and versatile, sturdy claws for grasping and climbing. Tree squirrels, unlike most mammals, can descend a tree head-first. They do so by rotating their ankles 180 degrees, enabling the hind paws to point backward and thus grip the tree bark from the opposite direction.

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 have an excellent sense of vision, which is especially important for the tree-dwelling species. Many also have a good sense of touch, with vibrissae on their limbs as well as their heads.
The teeth of sciurids follow the typical rodent pattern, with large incisors (for gnawing) that grow throughout life, and cheek teeth (for grinding) that are set back behind a wide gap, or diastema.
Many juvenile squirrels die in the first year of life. Adult squirrels can have a lifespan of 5 to 10 years in the wild. Some can survive 10 to 20 years in captivity. Premature death may be caused when a nest falls from the tree, in which case the mother may abandon her young if their body temperature is not correct. Many such baby squirrels have been rescued and fostered by a professional wildlife rehabilitator until they could be safely returned to the wild, although the density of squirrel populations in many places and the constant care required by premature squirrels means that few rehabilitators are willing to spend their time doing this and such animals are routinely euthanized instead.

Stated purposes of squirrels' tails, to benefit the squirrel, include: to keep rain, wind, or cold off itself; to cool off when hot, by pumping more blood through its tail; as a counterbalance when jumping about in trees; as a parachute when jumping.
The hairs from squirrel tails are prized in fly fishing when tying fishing flies. A special quality of squirrel tail hair is that it is all guard hairs, not undercoat.
When the squirrel is sitting upright, its tail folded up its back may stop predators looking from behind from seeing the characteristic shape of a small mammal.
Squirrels mate either once or twice a year and, following a gestation period of three to six weeks, give birth to a number of offspring that varies by species. The young are altricial, being born naked, toothless, and blind. In most species of squirrel, the female alone looks after the young, which are weaned at six to ten weeks and become sexually mature by the end of their first year. In general, the ground-dwelling squirrel species are social, often living in well-developed colonies, while the tree-dwelling species are more solitary.
Ground squirrels and tree squirrels are usually either diurnal or crepuscular, while the flying squirrels tend to be nocturnal—except for lactating flying squirrels and their young, which have a period of diurnality during the summer.

Because squirrels cannot digest cellulose, they must rely on foods rich in protein, carbohydrates, and fats. In temperate regions, early spring is the hardest time of year for squirrels because the nuts they buried are beginning to sprout (and thus are no longer available to eat), while many of the usual food sources have not yet become available. During these times, squirrels rely heavily on the buds of trees. Squirrels, being primarily herbivores, eat a wide variety of plants, as well as nuts, seeds, conifer cones, fruits, fungi, and green vegetation. Some squirrels, however, also consume meat, especially when faced with hunger. Squirrels have been known to eat small birds, young snakes, and smaller rodents, as well as bird eggs and insects. Some tropical squirrel species have shifted almost entirely to a diet of insects.
Squirrels, like pigeons and other fauna, are synanthropes, in that they benefit and thrive from their interaction in human environments. This gradual process of successful interaction is called synurbanization, wherein squirrels lose their inherent fear of humans in an urban environment. When squirrels were almost completely eradicated during the Industrial Revolution in New York, they were later re-introduced to "entertain and remind" humans of nature. The squirrel blended into the urban environment so efficiently that when synanthropic behavior stops (i.e. people do not leave trash outside during particularly cold winters), they can become aggressive in their search for food.

Aggression and predatory behavior has been observed in various species of ground squirrels, in particular the thirteen-lined ground squirrel. For example, Bernard 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. There has also been at least one 2005 report of squirrels preying on atypical animals, such as an incident where a pack of black squirrels killed and ate a large stray dog in Lazo, Russia. As well, squirrel attacks on humans are exceedingly rare, but do occur.
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 the stomachs of white-tailed antelope squirrels, 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.

Cream-coloured giant squirrel

The cream-coloured giant squirrel or pale giant squirrel is a large tree squirrel in the genus Ratufa found in forests in the Thai-Malay Peninsula, Sumatra (Indonesia), Borneo (Brunei, Indonesia and Malaysia) and nearby small islands. The species is near threatened and vulnerable to habitat degradation, and it has probably been extirpated in Singapore where the last sighting was in 1995. Reported sightings in Vietnam in 1984 are considered to be dubious.
The cream-coloured giant squirrel is one of the largest squirrels. It has a head–and–body length of 31–38 cm, a tail length of 37–44 cm and weighs 875–1,500 g. On average, adults of both sexes have a head–and–body length of about 34 cm and tail length of 42 cm, while females weight about 1,250 g and males 1,050 g.
As suggested by its name, the cream-coloured giant squirrel is typically overall cream to very light orangish-brown, while the underparts are whitish-cream.[4][6] In Borneo and nearby small islands where it is the only Ratufa giant squirrel, some populations resemble cream-coloured giant squirrels from elsewhere, but most have upperparts that are medium-dark grey, sometimes almost black (contrasting strongly with the whitish-cream underparts), the flanks and thighs can have a reddish-buff tinge and the cheeks are orangish.

The cream-coloured giant squirrel makes its home in lower montane and secondary forests, frequenting dipterocarp trees. It rarely enters plantations or settlements, preferring the forest. Although this squirrel primarily inhabits the upper canopy of the forest, it will at times come to ground in order to hunt smaller species of, or to cross gaps in the trees.
This species is diurnal, active from morning to evening. They live either in pairs or alone. When it is angry or shocked, it will give a loud sound that can be heard from afar.
Although this squirrel often will make holes in trees for shelter, during the breeding season it constructs a large globular drey (or nest) in tree branches, roughly the size of an eagle’s aerie. The young are born and raised in this nest.
The main dietary habits of Ratufa affinis are seeds, which it supplements with leaves, fruits, nuts, bark, insects, and eggs. The squirrel has a very short thumb that it uses to hold and control its food while feeding.
Unlike other tree squirrels, the cream-coloured giant squirrel does not sit upright with its tail arched over its back while feeding; instead, it balances itself with its hind feet on a branch so that its hands are free to control its food. In this position the axis of the squirrels body is held at right angles to the support, with its head and forequarters on one side of the branch, and the tail as a counterweight on the other side.

Black giant squirrel

The black giant squirrel or Malayan giant squirrel (Ratufa bicolor) is a large tree squirrel in the genus Ratufa native to the Indomalayan zootope. It is found in forests from northern Bangladesh, northeast India, eastern Nepal, Bhutan, southern China, Myanmar, Laos, Thailand, Malaysia, Cambodia, Vietnam, and western Indonesia (Java, Sumatra, Bali and nearby small islands).
The black giant squirrel is one of the largest species of squirrel in the world. On average, an adult black giant squirrel weighs around 1.05–1.25 kg, has a head–and–body length of 34–37 cm, and the tail is 41–42 cm long. The subspecies R. b. condorensis of Vietnam's Côn Sơn Island averages only c. 30 cm in head–and–body length and the tail 32 cm, but otherwise it resembles the typical subspecies.
This species is typically distinctly bicoloured with dark upperparts and pale underparts. The back, top of the head, ears and bushy tail are deep brown to black and the underparts are light buff-coloured. In Sumatra, Java and Bali the hairs of the back and tail are light-tipped, making these sections appear relatively pale (however, the back is still distinctly darker than the underparts). On small islands off Myanmar and in the Strait of Malacca the black giant squirrel has reddish-yellowish underparts.

Ratufa bicolor's range includes a variety of bioregions that all share the commonality of being forested. It ranges in elevation from sea level up to at least 1,400 metres, in some of the most rugged land in the world. However, in recent decades, R. bicolor's habitat has been steadily encroached upon by human settlement, timber harvesting and agriculture, which along with overhunting by human predation in parts of its range, has resulted in a total loss of up to 30% of the population in the past ten years. However, in some places this species is protected from hunting by law or tradition.
In South Asia R. bicolor dwells among tropical and subtropical coniferous and broadleaf forests. In Southeast Asia R. bicolor lives in tropical broadleaf evergreen and semi-evergreen forests, but is rarely seen in coniferous forests.In the tropical rai nforest of the Malay Peninsula and Indonesia, R. bicolor is not as abundant as elsewhere in its range, which is probably due to competition from other arboreal species (especially primates) for food in the upper forest canopy. Among the better places to sight the black giant squirrel is the Kaziranga National Park in the state of Assam, India.
R. bicolor is diurnal and arboreal, but sometimes climbs down from the forest canopy to feed on the ground. The black giant squirrel rarely enters plantations or settlements, preferring the wild forest. Its diet consists of seeds, pine cones, fruits, and leaves. It is primarily solitary, and has a litter of from 1 to 2 young, which it raises in a drey (or nest), often located within a hollow space of a tree.

Indian giant squirrel

The Indian giant squirrel or Malabar giant squirrel is a large tree squirrel species endemic to forests and woodlands in India. It is a diurnal, arboreal, and mainly herbivorous squirrel.
This species is endemic to India, with main sections of its distribution in the Western Ghats, Eastern Ghats and Satpura Range as far north as Madhya Pradesh. It is found at altitudes of 180–2,300 m in tropical deciduous, semi-deciduous (where often utilizing denser riparian growth), and moist evergreen forests and woodlands. In general, its distribution is fragmented because it is intolerant of habitat degradation. The Indian giant squirrel generally nests in taller trees with a mean height of 11 m in order to avoid predators.
The Indian giant squirrel is one of the largest squirrels with a head–and–body length of 25–50 cm, a tail that is about the same or somewhat longer, and a weight of 1.5–2 kg, although rarely up to 3 kg. Average for both sexes is about 36 cm in head–and–body length, 45 cm in tail length and 1.7–1.8 kg in weight. It has a conspicuous one-, two- or three-toned colour scheme. The colours involved can be whitish, creamy-beige, buff, tan, rust, reddish-maroon, brown, a dark seal brown or black. The underparts and the front legs are usually cream coloured, the head can be brown or beige, however there is a distinctive white spot between the ears. Otherwise the colours depend on the subspecies.

The Indian giant squirrel is an upper-canopy dwelling species, which rarely leaves the trees, and requires "tall profusely branched trees for the construction of nests."It travels from tree to tree with jumps of up to 6 m. When in danger, the Ratufa indica often freezes or flattens itself against the tree trunk, instead of fleeing. Its main predators are the birds of prey like owls and the leopard. The Giant Squirrel is mostly active in the early hours of the morning and in the evening, resting in the midday. They are typically solitary animals that only come together for breeding. The species is believed to play a substantial role in shaping the ecosystem of its habitat by engaging in seed dispersal. Diet includes fruit, flowers, nuts and tree bark. Some subspecies are omnivorous, also eating insects and bird eggs.
The Indian giant squirrel lives alone or in pairs. They build large globular nests of twigs and leaves, placing them on thinner branches where large predators can't get to them. These nests become conspicuous in deciduous forests during the dry season. An individual may build several nests in a small area of forest which are used as sleeping quarters, with one being used as a nursery.

Grizzled giant squirrel

The grizzled giant squirrel (Ratufa macroura) is a large tree squirrel in the genus Ratufa found in the highlands of the Central and Uva provinces of Sri Lanka, and in patches of riparian forest along the Kaveri River and in the hill forests of Karnataka, Tamil Nadu and Kerala states of southern India. The International Union for Conservation of Nature (IUCN) lists the species as near threatened due to habitat loss and hunting.
R. macroura is the smallest of the giant squirrels found in the Indian subcontinent, with a head and body length of 25 to 45 cm, and tail measuring roughly the same or more, for a total length of 50 to 90 cm. It has small rounded ears with pointed tufts. The home range of an individual is between 1,970 and 6,110 m2.
Subspecies dandolena is dorsally brown grizzled with white. Ventrally light brownish cream. Tail frosted with white fur. Forehead and feet are black in color. Whereas ssp. melamochra, upper parts are jet black which contrast brownish cream to orange yellow ventral surface. Tail frosted with black fur. Snout of both ssp. are pinkish color.
Their vision is good, which aids them in detecting predators. Their sense of hearing is relatively poor. The call is staccato and loud with repeated shrill cackle. It is usually uttered in morning and evening. A low "churr" is also used to communicate with nearby groups.

Hands are normally pentadactylous, with four digits and a rudimentary thumb. Fingers have large broad soft pads, where the inner pad is expanded for gripping while moving through branches. Feet are also comprised with soft pads with both fore and hind limbs possessing long, sharp claws.
Ratufa macroura are known to eat fruits, nuts, insects, bird eggs, and the bark of some trees. The fruit of the climber Combretum ovalifolium is an especially important food source where it occurs. Young squirrels, upon first emerging from the nest, have been observed to feed exclusively on this fruit.
Unlike its relatives, the giant squirrel balances using its two hind feet, instead of its tail.
The species is almost entirely an arboreal, very rarely coming to the ground to escape from predators, to flee from an intruder, attack males of the territory, and connecting with females.

Neotropical pygmy squirrel

The Neotropical pygmy squirrel is a South American species of tree squirrel, being the only living species in the genus Sciurillus and the subfamily Sciurillinae. Genetic analysis has shown it to be the sister group to all other squirrels.
The Neotropical pygmy squirrel is the smallest species of tree squirrel native to the Americas, measuring on average just 10 cm in head-body length, with an 11-cm tail. Adults weigh from 30 to 48 grams. The fur is grizzled grey over the body, with paler, but not sharply contrasting, fur on the underparts. The head is slightly reddish, with distinct white markings behind the ears, which are shorter and more rounded than on most other tree squirrels. The limbs are slender, with the fore limbs elongated to assist in climbing. Females have six teats.
Neotropical pygmy squirrels are diurnal and spend the day in the forest canopy, usually at least 9 m above the ground. They have been observed nesting in abandoned arboreal termite nests lined with fibres gathered from the machimango tree. They feed by gnawing on the bark of trees, especially those of the genus Parkia, and probably eating either the gummy exudates produced by the trees in response to injury or the cambium beneath the bark. Population densities are apparently low, with normally no more than three individual per km2, although groups containing more than one adult, plus young, have been observed in areas with a local concentration of food. These squirrels typically move rapidly through the trees, and are highly excitable, giving an alarm call described as similar to the sound of a cricket. They give birth to one or two young at a time, with pregnant females having been observed in June.

Tufted ground squirrel

The tufted ground squirrel or groove-toothed squirrel is a species of rodent in the family Sciuridae. It is the sole species in the genus Rheithrosciurus. It is found only on the island of Borneo. Confirmed elements of its diet include nuts, seeds and insects, for which it has been filmed foraging on the forest floor.
The squirrel's head and body measure about 335–352 mm long, with the tail measuring a further 299–342 mm long. It weighs about 1–2 kg. Its incisors have 7-10 distinctive longitudinal grooves. Its skull is also distinctive, being longer and flatter than most squirrels. The animal's dorsum is predominately brown with a reddish tone, and it has unusually hairy ears with large red to dark brown tufts. A longitudinal stripe of a white to buff to yellow colour, sometimes accompanied by a dark brown stripe, runs along the flank.
Rheithrosciurus is noted for having the largest known tail to body size ratio of any mammal, with the volume of its tail including the air included in the fluff being 130% of the volume of its body. (Compare 90% for the red squirrel.) It is unclear why the squirrel has such a large tail but scientists have suggested that it may have evolved to distract predators or to prevent them getting a firm grasp when attacking. It may alternatively have a function in communicating with other squirrels or in courtship. Other possible explanations, such as being used to keep the animal warm or for balance, seem unlikely as the squirrel lives on the ground in a warm region. The tail has a grizzled charcoal colour with white frosting and rises in a plume, with the longest hairs at the tip.

The species is known to live only on hillsides in lowland primary forest on the island of Borneo, at altitudes of under 1,100 metres. It has occasionally been seen in orchards and secondary forests but sightings are rare. Due to deforestation it is considered to be vulnerable and is totally protected in Sarawak, one of the two Malaysian states on Borneo. Hunting with a licence is legal in Sabah, the island's other Malaysian state. Some natives use the squirrel's tail to decorate the hilt of their parang knives.

Central American dwarf squirrel

The Central American dwarf squirrel, also known as Alfaro's pygmy squirrel, is a small tree squirrel in the genus Microsciurus and tribe Sciurini found in Colombia, Costa Rica, Nicaragua, and Panama. No species of squirrel within this genus are endangered, but they are rarely seen because they are shy and live hidden lives. This suggests that their population numbers may be larger than documented.
Central American dwarf squirrels are not as small as their name suggests. In fact, their body measurements are close to that of the Red Squirrel and Gray Squirrel, with a head-and-body length about 15 cm with a 12 cm long tail. The majority of their body is a dark, olive-green and brown color with a reddish-brown head coloration. The underside of their heads and limbs can range from a yellowish grey to a tawny grey color.
Central American dwarf squirrels are native to Colombia, Costa Rica, Nicaragua, and Panama. They typically inhabit tropical rainforests, with a preference for the heavy forest, particularly those with vines in the undergrowth, which can allow them to descend to the ground and quickly escape from predators.

Amazon dwarf squirrel

The Amazon dwarf squirrel is a chipmunk-sized tree squirrel native to South America.
As its name suggests, the Amazon dwarf squirrel is relatively small, with a head-body length of 12 to 16 cm and a tail 8 to 16 cm long. Adults weigh between 86 and 132 g, with males being slightly larger than females. The fur varies from reddish to dull brown, fading gradually to yellow or greyish on the underparts. There is a distinctive patch of pale yellow fur behind the ears, while the tail has faint yellowish bands and white frosting.
The limbs are unusually long for tree squirrels. In the forelimbs, the humerus and radius are of equal length, an adaptation thought to increase the squirrel's ability to climb large trees, compensating for a lack of shoulder mobility. The longer hindlimbs allow for stronger muscles, so that the squirrel can leap over larger gaps, relative to its size, than more typically sized squirrels can.
The squirrels are found in the upper Amazon Basin, broadly west of the Purus and Rio Negro rivers, in Brazil, Bolivia, Peru, Ecuador, and Colombia. They typically inhabit evergreen tropical rainforests at up to 2,000 m elevation, although they may sometimes be found in more disturbed habitats.

Santander dwarf squirrel

The Santander dwarf squirrel is a small tree squirrel endemic to Colombia.
The Santander dwarf squirrel is a small tree squirrel, measuring around 15 centimetres from nose to rump, with a tail about the same length again. Females are, on average, slightly larger than males. Originally described as a subspecies of the Andean squirrel, it is similar to that species in appearance, but somewhat smaller. It has reddish-orange fur over most of the body, with a black line running down the centre of the back and paler, pinkish-buff underparts. There are also paler markings on the snout and around the eyes. The tail is long and thin; the fur on the tail is relatively short, rather than bushy, and is tipped with white but otherwise black above and paler below. The precise range of the Santander dwarf squirrel is unclear, since it is often confused with the Andean squirrel. It was originally described from Santander Department in Colombia but has since also been reported from further west. It is, however, only known definitively from a patch of land between the middle section of the Magdalena River and the western slopes of the Cordillera Oriental. This region varies from 100 to 3,800 metres in elevation and is heavily forested, with oak dominating in the higher altitudes and more varied humid forest in the lowlands.
Very little is known about the behaviour or biology of the species, beyond the fact that it lives in trees and appears to be diurnal. The absence of reliable information, even on the exact area that it inhabits, meant that, as of 2016, it was not possible to assess its population, conservation status or any threats it might face, and it is therefore listed as data deficient by the IUCN.

Andean squirrel

The Andean squirrel is a tree squirrel endemic to Colombia where it inhabits montane rain forest and cloud forests of the Cordillera Occidental and Cordillera Central ranges of the Colombian Andes, at elevations between 2,000 and 3,300 metres. It is a small species with a body length of about 14 cm and a similar length tail. It has soft, silky, reddish-brown fur, a darker tail and yellowish-grey underparts. It is thought to be diurnal but has been little studied, and the International Union for Conservation of Nature has rated its conservation status as being data deficient.
The Andean squirrel is a typical tree squirrel, in its general proportions resembling the Eastern grey squirrel of North America. However, it is much smaller, with a body length of only about 14 centimetres, and a 12 to 16 centimetres tail. Although there are few records of its weight, it appears to be generally between about 100 and 140 grams. It has soft, silky, reddish-brown fur over most of the body, merging to greyish-yellow on the underparts. The tail fur is darker than that on the body, and some Andean squirrels also have a distinctive dark stripe down their flanks, and/or a black patch on the back of the head. Females have six teats.
It inhabits montane rain forest and cloud forests of the Cordillera Occidental and Cordillera Central of the Colombian Andes, at elevations between 2,000 and 3,300 metres. As a tree squirrel, it lives among Cecropia trees, palms, and tree ferns. It is believed to be diurnal, but sufficiently little is known about its habits, population, and habitat requirements, that it is currently listed as data deficient by the IUCN.

Bangs's mountain squirrel

Bangs's mountain squirrel is a poorly known species of tree squirrel, that only lives in Costa Rica and Panama. It can be found in mountain rain forests at an altitude between 1,900 and 2,600 metres, and lives mainly in the tree tops, but sometimes on the forest floor as well. One of its habitats is at the summit of the Poás Volcano in Costa Rica, in a Clusia forest that is almost inaccessible to humans.
The squirrel's head and body measure 15 centimetres, with a 13 centimetres tail. It has an olive brown back and an orange-red belly. Because of the shape of its skull and teeth, the species has been separated from the genus of typical tree squirrels, Sciurus, into its own genus Syntheosciurus.

Flying squirrel

Flying squirrels are a tribe of 50 species of squirrels in the family Sciuridae. They are not capable of flight in the same way as birds or bats but are able to glide from one tree to another with the aid of a patagium, a furry, parachute-like membrane that stretches from wrist to ankle. Their long tails provide stability in flight. Anatomically they are very similar to other squirrels but have a number of adaptations to suit their lifestyle; their limb bones are longer and their hand bones, foot bones, and distal vertebrae are shorter. Flying squirrels are able to steer and exert control over their glide path with their limbs and tail.
Molecular studies have shown that flying squirrels are monophyletic and originated some 18–20 million years ago. Most are nocturnal and omnivorous, eating fruit, seeds, buds, flowers, insects, gastropods, spiders, fungi, bird's eggs and tree sap. The young are born in a nest and are at first naked and helpless. They are cared for by their mother and by five weeks are able to practice gliding skills so that by ten weeks they are ready to leave the nest.
Flying squirrels are not capable of flight like birds or bats; instead, they glide between trees. They are capable of obtaining lift within the course of these flights, with flights recorded to 90 metres. The direction and speed of the animal in midair are varied by changing the positions of its limbs, largely controlled by small cartilaginous wrist bones. There is a cartilage projection from the wrist that squirrel holds upwards during a glide.

This specialized cartilage is only present in flying squirrels and not other gliding mammals. Possible origins for the styliform cartilage have been explored, and the data suggests that it is most likely homologous to the carpal structures that can be found in other squirrels. This cartilage along with the manus forms a wing tip to be used during gliding. After being extended, the wing tip may adjust to various angles, controlling aerodynamic movements. The wrist also changes the tautness of the patagium, a furry parachute-like membrane that stretches from wrist to ankle. It has a fluffy tail that stabilizes in flight. The tail acts as an adjunct airfoil, working as an air brake before landing on a tree trunk.

American red squirrel

The American red squirrel is one of three species of tree squirrels currently classified in the genus Tamiasciurus, known as the pine squirrels. The American red squirrel is variously known as the pine squirrel, North American red squirrel and chickaree. It is also referred to as Hudson's Bay squirrel, as in John James Audubon's work The Viviparous Quadrupeds of North America (hence the species name). The squirrel is a small, 200–250 g, diurnal mammal that defends a year-round exclusive territory. It feeds primarily on the seeds of conifer cones, and is widely distributed across North America wherever conifers are common, except on the Pacific coast, where its cousin, the Douglas squirrel, is found instead. The American red squirrel is not found on most of the Great Plains or in the southeastern United States, except for the Blue Ridge Mountains, as conifer trees are not common in those areas.
The squirrel has been expanding its range into hardwood forests.
Red squirrels can be easily distinguished from other North American tree squirrels by their smaller size, 28–35 cm total length (including tail), territorial behavior, and reddish fur with a white venter (underbelly). Red squirrels are somewhat larger than chipmunks.

The Douglas squirrel is morphologically similar to the American red squirrels, but has a rust-colored venter and is restricted to the southwestern coast of British Columbia and in the Pacific Northwest of the United States. The ranges of the American red squirrel and the Douglas squirrel overlap in southern British Columbia, northwestern Washington and eastern Oregon.
American red squirrels are primarily granivores, but incorporate other food items into their diets opportunistically. In Yukon, extensive behavioral observations suggest white spruce seeds comprise over 50% of a red squirrel's diet, but squirrels have also been observed eating spruce buds and needles, mushrooms, willow leaves, poplar buds and catkins, bearberry flowers and berries, and animal material such as bird eggs or even snowshoe hare leverets (young). White spruce cones mature in late July and are harvested by red squirrels in August and September. These harvested cones are stored in a central cache and provide energy and nutrients for survival over the winter and reproduction the following spring. The fallen scales from consumed seed cones can collect in piles, called middens, up to twelve meters across. White spruce exhibits two- to six-year masting cycles, where a year of superabundant cone production (mast year) is followed by several years in which few cones are produced. American red squirrel territories may contain one or several middens.

Eastern gray squirrel

The eastern gray squirrel, also known as the grey squirrel depending on region, is a tree squirrel in the genus Sciurus. It is native to eastern North America, where it is the most prodigious and ecologically essential natural forest regenerator. Widely introduced to certain places around the world, the eastern gray squirrel in Europe, in particular, is regarded as an invasive species.
The eastern gray squirrel has predominantly gray fur, but it can have a brownish color. It has a usual white underside as compared to the typical brownish-orange underside of the fox squirrel. It has a large bushy tail. Particularly in urban situations where the risk of predation is reduced, both white – and black-colored individuals are quite often found. The melanistic form, which is almost entirely black, is predominant in certain populations and in certain geographic areas, such as in large parts of southeastern Canada. Melanistic squirrels appear to exhibit a higher cold tolerance than the common gray morph; when exposed to −10 °C, black squirrels showed an 18% reduction in heat loss, a 20% reduction in basal metabolic rate, and an 11% increase to non-shivering thermogenesis capacity when compared to the common gray morph. The black coloration is caused by an incomplete dominant mutation of MC1R, where E+/E+ is a wild type squirrel, E+/EB is brown-black, and EB/EB is black.

The head and body length is from 23 to 30 cm, the tail from 19 to 25 cm, and the adult weight varies between 400 and 600 g. They do not display sexual dimorphism, meaning there is no gender difference in size or coloration.
The tracks of an eastern gray squirrel are difficult to distinguish from the related fox squirrel and Abert's squirrel, though the latter's range is almost entirely different from the gray's. Like all squirrels, the eastern gray shows four toes on the front feet and five on the hind feet. The hind foot-pad is often not visible in the track. When bounding or moving at speed, the front foot tracks will be behind the hind foot tracks. The bounding stride can be two to three feet long.

Fox squirrel

The fox squirrel, also known as the eastern fox squirrel or Bryant's fox squirrel, is the largest species of tree squirrel native to North America. Despite the differences in size and coloration, it is sometimes mistaken for American red squirrels or eastern gray squirrels in areas where the species co-exist.
The squirrel's total length measures 20 to 30 in, body length is 10 to 15 in, and a tail length that much again. They range in weight from 1.0 to 2.5 pounds. There is no sexual dimorphism in size or appearance. Individuals tend to be smaller in the west. There are three distinct geographical phases in coloration: In most areas the animals upper body is brown-grey to brown-yellow with a typically brownish-orange underside, while in eastern regions such as the Appalachians there are more strikingly-patterned dark brown and black squirrels with white bands on the face and tail. In the south can be found isolated communities with uniform black coats. To help with climbing, they have sharp claws, developed extensors of digits and flexors of forearms, and abdominal musculature. Fox squirrels have excellent vision and well-developed senses of hearing and smell. They use scent marking to communicate with other fox squirrels. "Fox squirrels also have several sets of vibrissae, hairs or whiskers that are used as touch receptors to sense the environment. These are found above and below their eyes, on their chin and nose, and on each forearm."

The fox squirrel's natural range extends through most of the eastern United States, north into the southern prairie provinces of Canada, and west to the Dakotas, Colorado, and Texas. They are absent (except for vagrants) in New England, New Jersey, most of New York, northern and eastern Pennsylvania, Ontario, Quebec, and the Atlantic provinces of Canada. They have been introduced to both northern and southern California, Oregon, Idaho, Montana, Washington, and New Mexico, as well as Ontario and British Columbia in Canada. While very versatile in their habitat choices, fox squirrels are most often found in forest patches of 40 hectares or less with an open understory, or in urban neighborhoods with trees. They thrive best among oak, hickory, walnut, pecan and pine trees, storing their nuts for winter. Western range extensions in Great Plains regions such as Kansas are associated with riverine corridors of cottonwood. A subspecies native to several eastern US states is the Delmarva fox squirrel.
Fox squirrels are most abundant in open forest stands with little understory vegetation; they are not found in stands with dense undergrowth. Ideal habitat is small stands of large trees interspersed with agricultural land. The size and spacing of pines and oaks are among the important features of fox squirrel habitat. The actual species of pines and oaks themselves may not always be a major consideration in defining fox squirrel habitat. Fox squirrels are often observed foraging on the ground several hundred meters from the nearest woodlot. Fox squirrels also commonly occupy forest edge habitat.

Red squirrel

The red squirrel or Eurasian red squirrel is a species of tree squirrel in the genus Sciurus common throughout Eurasia. The red squirrel is an arboreal, primarily herbivorous rodent.
In Great Britain, Ireland, and in Italy numbers have decreased drastically in recent years. This decline is associated with the introduction by humans of the eastern grey squirrel from North America. However, the population in Scotland is stabilisingdue to conservation efforts, awareness and the increasing population of the pine marten, a European predator that selectively controls grey squirrels.
The red squirrel has a typical head-and-body length of 19 to 23 cm, a tail length of 15 to 20 cm, and a mass of 250 to 340 g. Males and females are the same size. The red squirrel is somewhat smaller than the eastern grey squirrel which has a head-and-body length of 25 to 30 cm and weighs between 400 and 800 g.
The long tail helps the squirrel to balance and steer when jumping from tree to tree and running along branches and may keep the animal warm during sleep.
The red squirrel, like most tree squirrels, has sharp curved claws to help it to climb and descend broad tree trunks, thin branches, and even house walls. Its strong hind legs let it leap gaps between trees. The red squirrel also can swim.

The coat of the red squirrel varies in colour with time of year and location. There are several coat colour morphs ranging from black to red. Red coats are most common in Great Britain; in other parts of Europe and Asia different coat colours co-exist within populations, much like hair colour in some human populations. The underside of the squirrel is always white-cream in colour. The red squirrel sheds its coat twice a year, switching from a thinner summer coat to a thicker, darker winter coat with noticeably larger ear-tufts (a prominent distinguishing feature of this species) between August and November. A lighter, redder overall coat colour, along with the ear-tufts (in adults) and smaller size, distinguish the Eurasian red squirrel from the American eastern grey squirrel. The red colour is for camouflage when seen against the bark of pine trees.
Red squirrels occupy boreal, coniferous woods in northern Europe and Siberia, preferring Scots pine, Norway spruce and Siberian pine. In western and southern Europe they are found in broad-leaved woods where the mixture of tree and shrub species provides a better year-round source of food. In most of the British Isles and in Italy, broad-leaved woodlands are now less suitable due to the better competitive feeding strategy of introduced grey squirrels.

Western gray squirrel

The western gray squirrel is an arboreal rodent found along the western coast of the United States and Mexico. It is a tree squirrel.
In some places, this species has also been known as the silver-gray squirrel, the California gray squirrel, the Oregon gray squirrel, the Columbian gray squirrel and the banner-tail. There are three geographical subspecies: Sciurus griseus griseus (central Washington to the western Sierra Nevada in central California); S. g. nigripes (from south of San Francisco Bay to San Luis Obispo County, California); and S. g. anthonyi (which ranges from San Luis Obispo to northern Baja California).
The western gray squirrel was first described by George Ord in 1818 based on notes taken by Lewis and Clark at The Dalles in Wasco County, Oregon.
Sciurus griseus is the largest tree squirrel in the Sierra Nevada and Central California range. It has plantigrade, pentadactyl feet with two phalanges. Compared with the eastern gray squirrel S. carolinensis or the fox squirrel S. niger (which have been introduced into its native range), these squirrels are shy, and will generally run up a tree and give a hoarse chirping call when disturbed. Weights vary from about .35 to 1 kilogram, and length (including tail) from 43 to 61 centimetres. It is the largest native tree squirrel in the western coastal United States. Western gray squirrels exhibit a form of coloration known as counter shading. The dorsal fur is a silver gunmetal gray, with pure white on the underside; there may be black flecks in the tail. Ears are large but without tufts.