squirrel

—squirrelish, squirrellike, adj.

/skwerr"euhl, skwur"-/ or, esp. Brit., /skwir"euhl/, n., pl. squirrels, (esp. collectively) squirrel, v., squirreled, squirreling or (esp. Brit.) squirrelled, squirrelling.

n.

1. any of numerous arboreal, bushy-tailed rodents of the genus Sciurus, of the family Sciuridae.

2. any of various other members of the family Sciuridae, as the chipmunks, flying squirrels, and woodchucks.

3. the meat of such an animal.

4. the pelt or fur of such an animal: a coat trimmed with squirrel.

v.t.

5. to store or hide (money, valuables, etc.), usually for the future (often fol. by away): I've squirreled away a few dollars for an emergency.

[1325-75; ME squirel < AF escuirel (OF escuireul) VL *scurellus, *scuriolus, repr. L sciurus ( < Gk skíouros lit., shadow-tailed (ski(á) shadow + -ouros, adj. deriv. of ourá tail); appar. so called because the tail was large enough to provide shade for the rest of the animal) with dim. suffixes -ellus, -olus]

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I

Any of about 260 species in 50 genera (family Sciuridae) of mostly diurnal rodents found almost worldwide.

Many species are arboreal; some are terrestrial. All species have strong hind legs and a hairy tail. They vary widely in colour and form and range in total length from the 4-in. (10-cm) African pygmy squirrel to the giant squirrels of Asia, about 35 in. (90 cm) long. Tree dwellers live in a tree hollow or nest, and most are active year-round. Ground dwellers live in burrows, and many become dormant in winter (hibernate) or summer (estivate). Most species are primarily vegetarian and are fond of seeds and nuts; some eat insects or supplement their diet with animal protein. See also chipmunk; flying squirrel; ground squirrel; marmot; prairie dog.

II

(as used in expressions)

flying squirrel

ground squirrel

squirrel monkey

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▪ rodent

Introduction

      generally, any of the 50 genera and 268 species of rodents whose common name is derived from the Greek skiouros, meaning “shade tail,” which describes one of the most conspicuous and recognizable features of these small mammals. These distinctive animals occupy a range of ecological niches worldwide virtually anywhere there is vegetation. The squirrel family includes ground squirrels (ground squirrel), chipmunks (chipmunk), marmots (marmot), prairie dogs (prairie dog), and flying squirrels (flying squirrel), but to most people squirrel refers to the 122 species of tree squirrels, which belong to 22 genera of the subfamily Sciurinae. The North American gray squirrel (Sciurus carolinensis) has adapted to urban and suburban areas where it is regarded as aesthetic or as a minor annoyance. In northern Europe the red squirrel (S. vulgaris) is valued for its soft, thick fur. Villagers in tropical forests keep squirrels as pets. Most species are hunted for food.

General features

      Tree squirrels have slender, lanky bodies, long, muscular limbs, and furred feet. The forefeet have four long digits plus a short, stubby thumb, and the five-toed hind feet are narrow or moderately wide. The bald soles of the feet take the form of prominent, fleshy pads. Because the ankle joints are flexible and can be rotated, squirrels can rapidly descend trees headfirst with the hind feet splayed flat against the trunk. Their large, bright eyes convey an alert demeanour, and the broad, short head tapers to a blunt muzzle adorned with long whiskers. The rounded ears, small in relation to body size, are densely covered with short, fine hairs, which form a long tuft at the tips of the ears in some species. The tail is about as long as head and body or appreciably longer. Furred from base to tip, the tail appears bushy and cylindrical when the hairs grow evenly around the tail; the tail appears flatter if the fur originates only from opposite sides. Claws are large, strong, curved, and very sharp, which enables tree squirrels to navigate vertical surfaces and slim branches.

      Variation in body size is considerable. Largest are the four species of Oriental giant squirrels (genus Ratufa) native to the tropical forests (tropical rainforest) of Southeast Asia. Weighing 1.5 to 3 kg (3 to almost 7 pounds), it has a body length of 25 to 46 cm (about 10 to 18 inches) and a tail about as long. Two species of pygmy squirrels are the smallest: the neotropical pygmy squirrel (Sciurillus pusillus) of the Amazon Basin (Amazon River) weighs 33 to 45 grams (1 to 1.5 ounces), with a body 9 to 12 cm long and an equally long tail; but the African pygmy squirrel (Myosciurus pumilio) of the West African tropical forests is even smaller, at 13 to 20 grams, with a body length of 6 to 8 cm and a somewhat shorter tail.

      Squirrels' soft, dense fur is moderately long in most species but can be very long and almost shaggy in some. Colour is extraordinarily variable. Some species are plain, covered in one or two solid shades of brown or gray. A few species are striped along the sides and back; sometimes the head is also striped. Tropical species exhibit combinations of white, gray, yellow, orange, red, maroon, brown, and black, yielding a variety of complex coat patterns.

Natural history

 All tree squirrels are diurnal and arboreal, but the range of vertical activity in species differs widely, especially among those living in tropical rainforests. Some, such as the Oriental giant squirrels (genus Ratufa) and the African giant squirrels (genus Protoxerus), rarely descend from the high canopy. Others, like the pygmy squirrel of Sulawesi (Celebes) (Prosciurillus murinus), travel and forage at intermediate levels between ground and canopy. Some large tropical squirrels, such as the Sulawesi giant squirrel (Rubrisciurus rubriventer) and the northern Amazon red squirrel (Sciurus igniventris), nest at middle levels but travel and forage low in the understory or on the ground. The African palm squirrels (genus Epixerus) are long-legged runners that forage only on the ground. Certain species, such as the red-tailed squirrel (S. granatensis) of the American tropics and the African pygmy squirrel, are active from ground to canopy. In the United States, the Eastern fox squirrel (S. niger) runs along the ground from tree to tree, but others, including the Eastern gray squirrel (S. carolinensis), prefer to travel through the treetops and regularly cross rivers by swimming with the head up and tail flat on the water's surface. Thomas's rope squirrel (Funisciurus anerythrus) of Africa even submerges itself and swims underwater.

      Most tree squirrels have strong chisel-like incisors and powerful jaws, which are required for gnawing open the hard nuts that, along with fruits, are a primary component of their diet. They also eat seeds, fungi, insects and other arthropods, the cambium layer of tree bark, nectar, leaves, buds, flowers, and sometimes bird eggs, nestlings, and carrion. Some red squirrels (genus Tamiasciurus) and Sciurus species of temperate climates will stalk, kill, and eat other squirrels, mice, and adult birds and rabbits for food, but such predation in tropical tree squirrels seems rare.

      Nests (nest) are constructed among branches in the forest canopy or at lower levels in tree crowns, vine tangles, tree hollows, or undergrowth near the ground. Some species of tropical tree squirrels produce several litters per year; breeding season in the Northern Hemisphere may extend from December to September and may result in one or two litters that average three to seven young, depending upon the species.

      In the New World, tree squirrels range from the boreal forests (boreal forest) of Canada and Alaska southward through coniferous and deciduous woodlands in the United States to the tropical rainforests of South America. In Africa, tree squirrels are native to rainforests and some woodland savannas. Their distribution in the remainder of the Old World extends from the northern boreal forests of Europe and Asia to the Indonesian tropical rainforests. East of the Asian continental margin, tree squirrels inhabit the forests of Taiwan, some islands in the Philippines, and Sulawesi, but they do not occur naturally anywhere east of those islands. Most of the species in 20 of the 22 genera are found in tropical rainforests.

Classification and evolutionary history

      Tree squirrels belong to the subfamily Sciurinae; it and the subfamily Pteromyinae (flying squirrels (flying squirrel)) constitute the family Sciuridae of the order Rodentia. Fossils record the evolutionary history of tree squirrels back to the Late Eocene Epoch (41.3 million to 33.7 million years ago) in North America and the Miocene Epoch (23.8 million to 5.3 million years ago) in Africa and Eurasia.

Family Sciuridae (squirrels)

 2 subfamilies comprising 272 species in 51 genera found worldwide. See flying squirrel for 15 genera and 42 species of subfamily Pteromyinae. See also ground squirrel.

      Subfamily Sciurinae

 230 species in 36 genera, including ground squirrels (ground squirrel) (10 genera, 62 species), marmots (marmot) (1 genus, 14 species), chipmunks (chipmunk) (1 genus, 25 species), Asian rock squirrels (1 genus, 2 species), and prairie dogs (prairie dog) (1 genus, 5 species).

      Tree squirrels

 122 species in 22 genera.

      Genus Sciurus (tree squirrels)

 28 non-African species.

      Genus Callosciurus (Oriental, or tricoloured, tree squirrels)

 15 Southeast Asian species.

      Genus Sundasciurus (Sunda squirrels)

 15 Southeast Asian species.

      Genus Paraxerus (bush squirrels)

 11 African species.

      Genus Funisciurus (rope, or African striped, squirrels)

 9 African species.

      Genus Heliosciurus (sun squirrels)

 6 African species.

      Genus Funambulus (Asiatic palm squirrels)

 5 Asian species.

      Genus Microsciurus (dwarf squirrels)

 4 Central and South American species.

      Genus Prosciurillus (Sulawesi dwarf squirrels)

 4 Southeast Asian species.

      Genus Ratufa (Oriental giant squirrels)

 4 Indian and Southeast Asian species.

      Genus Tamiops (Asiatic striped squirrels)

 4 Southeast Asian species.

      Genus Tamiasciurus (red squirrels or chickarees)

 3 North American species.

      Genus Exilisciurus (pygmy squirrels)

 3 Southeast Asian species.

      Genus Epixerus (African palm squirrels)

 2 West African species.

      Genus Protoxerus (oil palm squirrels or African giant squirrels)

 2 African species.

      Genus Sciurillus (neotropical pygmy squirrel)

 1 Amazonian species.

      Genus Rubrisciurus (Sulawesi giant squirrel)

 1 Southeast Asian species.

      Genus Nannosciurus (black-eared squirrel)

 1 Southeast Asian species.

      Genus Myosciurus (African pygmy squirrel)

 1 West African species.

      Genus Rheithrosciurus (tufted, or groove-toothed, ground squirrel)

 1 Southeast Asian species found only on Borneo.

      Genus Glyphotes (sculptor squirrel)

 1 Southeast Asian species found only on Borneo.

      Genus Syntheosciurus (Bang's mountain squirrel)

 1 species found only in Costa Rica and Panama.

Guy Musser

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