Squirrels
Squirrels
The squirrel family (Sciuridae) is a diverse group of about 44 genera of rodents, including the“true” or tree squirrels, as well as flying squirrels, ground squirrels, chipmunks, marmots, groundhog, and prairie dogs. Members of the squirrel family occur in North and South America, Africa, Eurasia, and Southeast Asia, but not in Madagascar, New Guinea, Australia, or New Zealand.
The squirrel family encompasses species that are exclusively arboreal, living in tropical, temperate, or boreal forests. It also includes species that are exclusively terrestrial, living in burrows in the ground in alpine or arctic tundra, semiarid desert, prairie, or forest edges. Most squirrels are diurnal, but a few, such as the flying squirrels, are nocturnal. Most squirrels are largely herbivorous, eating a wide variety of plant tissues. Some species, however, supplement their diet with insects, bird eggs, and nestlings.
The following sections describe most of the major groups in the squirrel family, with an emphasis on species occurring in North America.
Tree squirrels
There are about 55 species of tree squirrels in the genus Sciurus, that occur in Asia, Europe, North America, and South America. As their name suggests, tree squirrels are highly arboreal animals, living in forests of all types, from the limits of trees in the north, to the tropics.
Tree squirrels have a long, bushy tail, used as a rudder when they are airborne while leaping from branch to branch and as a comfy wrap-around when the animal is sleeping. Tree squirrels forage during the day. They eat a wide range of plant tissues, but are partial to the flowers, nuts, and fruits of trees, sometimes foraging on the ground to obtain these after they have fallen. They may also feed on insects, bird eggs, and nestlings.
Tree squirrels utter a loud barking chatter when alarmed, often accompanied by an agitated fluttering of their tail. Their color varies from black through red, brown, and gray, often with whitish underparts. Tree squirrels do not hibernate, but they may sleep deeply in their arboreal nests for several days running during inclement winter weather.
The eastern gray squirrel (Sciurus carolinensis) is a widespread species in eastern North America. Although gray is the most common color of the pelage of this
species, black-colored animals also occur, and these can be dominant in many eastern populations. The gray squirrel is found mostly in temperate angiosperm and mixed conifer-hardwood forests, but it has also adapted well to habitats available in the urban forests of older, more-mature neighborhoods.
The western gray squirrel (S. griseus) occurs in oak and oak-pine forests of the western states. The eastern fox squirrel (S. niger) is a resident of hardwood forests of the eastern United States. This relatively large gray or rusty-yellowish colored species is commonly hunted as a small-game animal. The tassel-eared or Kaibab squirrel (S. alberti) occurs in pine forests of upland plateaus of the central southwestern States, and has long, distinctive, tufts of hair on the tops of its ears.
Red squirrels
The two species of red squirrel (Tamiasciurus spp.), also known as chickarees and pine squirrels, are widespread arboreal animals occurring in conifer-dominated forests of North America, and to a lesser degree in mixed-wood forests. Red squirrels do not hibernate and are active all winter. However, during bad weather they may sleep for several days in their tree-top nest, usually located in a fork of a branch or in a hollow part of a tree. Red squirrels eat a wide range of nuts, fruits, flowers, coniferseeds, and mushrooms, as well as opportunistically predating on insects and bird nests.
The red squirrel (Tamiasciurus hudsonicus) is quite widespread in boreal, montane, and pine forests. The range of this species extends from the northern limit of trees in Canada and Alaska, southward through the Appalachian Mountains to South Carolina, and in the Rocky Mountains to New Mexico. This species has reddish fur and white underparts and feet.
The Douglas squirrel, or chickaree (Tamiasciurus douglasii), occurs in conifer-dominated and mixed-wood forests, and ranges from British Columbia south to California. This species stores large caches of conifer cones for use as food during the wintertime.
Marmots
Marmots, along with the groundhog, are species of stocky, ground-dwelling animals in the genus Marmota. Marmots live in rocky crevices, or in burrows that they dig in sandy-loam soil. Most marmot species occur in alpine or arctic tundra, or in open forests of North America or Eurasia, although the groundhog is also a familiar species of agricultural landscapes. Marmots eat the tissues of a wide range of herbaceous and woody plants, and they store food in their dens, especially for consumption during the winter. Marmots become very fat prior to their winter-time hibernation, and then lose weight steadily until the spring.
The most widespread species in North America is the groundhog or woodchuck (Marmota monax), which is a common animal of open habitats over eastern and central regions of the continent. The ground-hog is a reddish or brownish, black-footed marmot, typically weighing 7-13 lb (3-6 kg). These animals dig their burrow complexes in open places in well-drained soil, usually on the highest ground available.
The hoary marmot (M. caligata) occurs in alpine tundra and upper montane forest in the northwestern United States, and north to the arctic tundra of Alaska and Yukon. The yellow-bellied marmot (M. flaviventris) is a species of alpine and open montane habitats of the western United States.
Prairie dogs
Prairie dogs are species of ground-living herbivores in the genus Cynomys, occurring in open, arid prairie and grasslands of North America. Prairie dogs are highly social, living in complexes of burrows known as towns, which can contain thousands of animals. Within these larger populations, the social structure involves smaller family units known as coteries, each of which includes a breeding male, a harem of females, and immature youngsters. Prairie dogs feed on many species of plants, and because of the large population densities in their towns, they can greatly change the nature of the vegetation in their habitat.
The most widespread species is the black-tailed prairie dog (Cynomys ludovicianus )of dry prairies from southern Saskatchewan to northern Mexico. The white-tailed prairie dog (Cynomys leucurus ) occurs in grasslands of upland plateaus at higher elevation, in Colorado, Montana, Utah, and Wyoming.
Ground squirrels
Ground squirrels, gophers, or diggers are species of ground-dwelling rodents in the genus Citellus. These animals occur through much of western and northern North America and northern Eurasia. They typically have a grizzled, yellowish or grayish fur, often decorated with white spots or stripes. Ground squirrels eat seeds, fruits, foliage, and underground tissues of herbaceous plants, and they have internal cheek pouches to carry food to storage chambers in their underground burrows. Ground squirrels become very fat by the end of the summer, and they spend the winter in hibernation.
Various species of ground squirrels occur in western North America, only some of which are mentioned here. The thirteen-lined ground squirrel (Citellus tridecemlineatus ) is the widest-ranging species, occurring in shortgrass prairie and rangelands over much of the central United States and the southern prairie provinces of Canada. The Townsend ground squirrel (C. townsendi )occurs in dry, upland habitats of the western United States, while Richardson’s ground squirrel (C. richardsonii ) occurs in similar habitats farther to the north. The Arctic ground squirrel (C. undulatus ) occurs in open boreal forest and low-arctic tundra west of Hudson Bay as far as Alaska. This species is sometimes called the parka ground squirrel, because its fur is sometimes used to line the edges of the hood and sleeves of parkas.
The California rock, or canyon, ground squirrels are a group of five closely related species occurring from Washington to northern Mexico, and as far east as Texas and Colorado. The California ground squirrel (Spermophilus beecheyi ) occurs in clearings in conifer forests in the Sierra Nevada of California. The rock squirrel (S. variegatus ) has a wider range, and occurs in rocky canyons and talus slopes. Some taxonomists place these animals in the genus Otospermophilus.
The golden-mantled ground squirrels, or copperheads, are relatively small animals. Citellus lateralis is a species living in alpine tundra and open conifer forest of the Rocky Mountains and associated ranges from western Canada south to California. Some taxonomists place this group of ground squirrels in their own genus, Callospermophilus.
KEY TERMS
Diurnal —Refers to animals that are mainly active in the daylight hours.
Herbivore —An animal that only eats plant foods.
Hibernation —A deep, energy-conserving sleep that some mammals enter while passing the winter-time. In most species, hibernation is characterized by significantly slowed metabolic rates, and sometimes a fall in the core body temperature.
Antelope ground squirrels
The antelope ground squirrels, or antelope chipmunks, are five relatively small species of arid habitats in the southwestern United States. These animals have a gray or reddish-brown coat, with a narrow white line running along each side of the body. The white-tail antelope squirrel (Ammospermophilus leucurus ) occurs in desert and dry foothills of parts of the southwestern United States, Baja, and central Mexico. The Yuma antelope squirrel (A. harrisi ) occurs in similar habitat in Arizona and northwestern Mexico.
Chipmunks
The American chipmunk (Tamias striatus ) occurs in angiosperm-dominated forest through much of the eastern United States and southeastern Canada. Chipmunks live in burrows that they dig into the ground, and they have large cheek pouches used to carry food into their den.
The western chipmunks are a more diverse group of about sixteen species occurring through most of North America, especially in the west, as well as in northeastern Asia. The most widespread species is the least chipmunk (Tamias minimus ), a familiar species of a wide range of forest types, and a friendly animal at campgrounds. The yellow pine chipmunk (T. amonoeus ) is a widespread western species.
Flying squirrels
There are various types of flying squirrels, especially in tropical forests. However, those of the Americas are two species in the genus Glaucomys. Flying squirrels are nocturnal animals. They nest in cavities in trees, and are proficient at gliding from higher to lower parts of trees, using a wide flap of skin stretching between their legs as their aerodynamic“wings.” These animals feed on a variety of seeds, nuts, and fruits, and insects, bird eggs, and fledglings when available. The southern flying squirrel (G. volans ) occurs in a wide range of forest types throughout southeastern North America. The northern flying squirrel (G. sabrinus) occurs farther to the north, and ranges across North America.
Resources
BOOKS
Banfield, A.W.F. The Mammals of Canada. Toronto, Ontario: University of Toronto Press, 1974.
Barash, D. Marmots: Social Behavior and Ecology. Stanford CA: California University Press, 1989.
Gurnell, J. The Natural History of Squirrels. London: Christopher Helm, 1987.
Hall, E.R. The Mammals of North America. 2nd ed. New York: Wiley & Sons, 1981.
Nowak, R. M., ed. Walker’s Mammals of the World. 6th ed. Baltimore: Johns Hopkins University Press, 1999.
Steele, M.A., and J. Koprowski. North American Tree Squirrels. Washington, DC: Smithsonian Institution Press, 2001.
Steele, M.A., J.F. Merritt, and D.A. Zegers, eds. Ecology and Evolutionary Biology of Tree Squirrels. Martinsville, VA: Virginia Museum of Natural History Special Publication no. 6, 1998.
Wilson, D.E., and D. Reeder. Mammal Species of the World. 3rd ed. Washington, DC: Smithsonian Institution Press, 2005.
Bill Freedman
Squirrels
Squirrels
The squirrel family (Sciuridae) is a diverse group of about 50 genera of rodents , including the "true" or tree squirrels, as well as flying squirrels, ground squirrels, chipmunks , marmots , woodchuck, and prairie dogs. Members of the squirrel family occur in North and South America , Africa , Eurasia, and Southeast Asia , but not in Madagascar, New Guinea, Australia , or New Zealand.
The squirrel family encompasses species that are exclusively arboreal, living in tropical, temperate, or boreal forests . It also includes species that are exclusively terrestrial, living in burrows in the ground in alpine or arctic tundra , semiarid desert , prairie, or forest edges. Most squirrels are diurnal, but a few, such as the flying squirrels, are nocturnal. Most squirrels are largely herbivorous, eating a wide variety of plant tissues. Some species, however, supplement their diet with insects , bird eggs, and nestlings.
The following sections describe most of the major groups in the squirrel family, with an emphasis on species occurring in North America .
Tree squirrels
There are about 55 species of tree squirrels in the genus Sciurus, that occur in Asia, Europe , North America, and South America. As their name suggests, tree squirrels are highly arboreal animals, living in forests of all types, from the limits of trees in the north, to the tropics.
Tree squirrels have a long, bushy tail, used as a rudder when they are airborne while leaping from branch to branch and as a comfy wrap-around when the animal is sleeping. Tree squirrels forage during the day. They eat a wide range of plant tissues, but are partial to the flowers, nuts, and fruits of trees, sometimes foraging on the ground to obtain these after they have fallen. They may also feed on insects, bird eggs, and nestlings.
Tree squirrels utter a loud barking chatter when alarmed, often accompanied by an agitated fluttering of their tail. Their color varies from black through red, brown, and grey, often with whitish underparts. Tree squirrels do not hibernate, but they may sleep deeply in their arboreal nests for several days running during inclement winter weather .
The eastern grey squirrel (Sciurus carolinensis) is a widespread species in eastern North America. Although grey is the most common color of the pelage of this species, black-colored animals also occur, and these can be dominant in many eastern populations. The grey squirrel is found mostly in temperate angiosperm and mixed conifer-hardwood forests, but it has also adapted well to habitats available in the urban forests of older, more-mature neighborhoods.
The western grey squirrel (S. griseus) occurs in oak and oak-pine forests of the western states. The eastern fox squirrel (S. niger) is a resident of hardwood forests of the eastern United States. This relatively large grey or rusty-yellowish colored species is commonly hunted as a small-game animal. The tassel-eared or Kaibab squirrel (S. alberti) occurs in pine forests of upland plateaus of the central southwestern States, and has long, distinctive, tufts of hair on the tops of its ears.
Red squirrels
The two species of red squirrel (Tamiasciurus spp.), also known as chickarees and pine squirrels, are widespread arboreal animals occurring in conifer-dominated forests of North America, and to a lesser degree in mixed-wood forests. Red squirrels do not hibernate and are active all winter. However, during bad weather they may sleep for several days in their tree-top nest, usually located in a fork of a branch or in a hollow part of a tree. Red squirrels eat a wide range of nuts, fruits, flowers, conifer seeds , and mushrooms , as well as opportunistically predating on insects and bird nests.
The red squirrel (Tamiasciurus hudsonicus) is quite widespread in boreal, montane, and pine forests. The range of this species extends from the northern limit of trees in Canada and Alaska, southward through the Appalachian Mountains to South Carolina, and in the Rocky Mountains to New Mexico. This species has reddish fur and white underparts and feet.
The Douglas squirrel, or chickaree (Tamiasciurus douglasii), occurs in conifer-dominated and mixed-wood forests, and ranges from British Columbia south to California. This species stores large caches of conifer cones for use as food during the wintertime.
Marmots
Marmots, along with the groundhog , are species of stocky, ground-dwelling animals in the genus Marmota. Marmots live in rocky crevices, or in burrows that they dig in sandy-loam soil . Most marmot species occur in alpine or arctic tundra, or in open forests of North America or Eurasia, although the groundhog is also a familiar species of agricultural landscapes. Marmots eat the tissues of a wide range of herbaceous and woody plants, and they store food in their dens, especially for consumption during the winter. Marmots become very fat prior to their wintertime hibernation , and then lose weight steadily until the spring.
The most widespread species in North America is the groundhog or woodchuck (Marmota monax), which is a common animal of open habitats over eastern and central regions of the continent . The groundhog is a reddish or brownish, black-footed marmot, typically weighing 7-13 lb (3-6 kg). These animals dig their burrow complexes in open places in well-drained soil, usually on the highest ground available.
The hoary marmot (M. caligata) occurs in alpine tundra and upper montane forest in the northwestern United States, and north to the arctic tundra of Alaska and Yukon. The yellow-bellied marmot (M. flaviventris) is a species of alpine and open montane habitats of the western United States.
Prairie dogs
Prairie dogs are species of ground-living herbivores in the genus Cynomys, occurring in open, arid prairie and grasslands of North America. Prairie dogs are highly social, living in complexes of burrows known as towns, which can contain thousands of animals. Within these larger populations, the social structure involves smaller family units known as coteries, each of which includes a breeding male, a harem of females, and immature youngsters. Prairie dogs feed on many species of plants, and because of the large population densities in their towns, they can greatly change the nature of the vegetation in their habitat .
The most widespread species is the black-tailed prairie dog (Cynomys ludovicianus) of dry prairies from southern Saskatchewan to northern Mexico. The whitetailed prairie dog (Cynomys leucurus) occurs in grasslands of upland plateaus at higher elevation, in Colorado, Montana, Utah, and Wyoming.
Ground squirrels
Ground squirrels, gophers , or diggers are species of ground-dwelling rodents in the genus Citellus. These animals occur through much of western and northern North America and northern Eurasia. They typically have a grizzled, yellowish or grayish fur, often decorated with white spots or stripes. Ground squirrels eat seeds, fruits, foliage, and underground tissues of herbaceous plants, and they have internal cheek pouches to carry food to storage chambers in their underground burrows. Ground squirrels become very fat by the end of the summer, and they spend the winter in hibernation.
Various species of ground squirrels occur in western North America, only some of which are mentioned here. The thirteen-lined ground squirrel (Citellus tridecemlineatus) is the widest-ranging species, occurring in short-grass prairie and rangelands over much of the central United States and the southern prairie provinces of Canada. The Townsend ground squirrel (C. townsendi) occurs in dry, upland habitats of the western United States, while Richardson's ground squirrel (C. richard-sonii) occurs in similar habitats farther to the north. The Arctic ground squirrel (C. undulatus) occurs in open boreal forest and low-arctic tundra west of Hudson Bay as far as Alaska. This species is sometimes called the parka ground squirrel, because its fur is sometimes used to line the edges of the hood and sleeves of parkas.
The California rock, or canyon, ground squirrels are a group of five closely related species occurring from Washington to northern Mexico, and as far east as Texas and Colorado. The California ground squirrel (Spermophilus beecheyi) occurs in clearings in conifer forests in the Sierra Nevada of California. The rock squirrel (S. variegatus) has a wider range, and occurs in rocky canyons and talus slopes. Some taxonomists place these animals in the genus Otospermophilus.
The golden-mantled ground squirrels, or copperheads, are relatively small animals. Citellus lateralis is a species living in alpine tundra and open conifer forest of the Rocky Mountains and associated ranges from western Canada south to California. Some taxonomists place this group of ground squirrels in their own genus, Callospermophilus.
Antelope ground squirrels
The antelope ground squirrels, or antelope chipmunks, are five relatively small species of arid habitats in the southwestern United States. These animals have a grey or reddish-brown coat, with a narrow white line running along each side of the body. The white-tail antelope squirrel (Ammospermophilus leucurus) occurs in desert and dry foothills of parts of the southwestern United States, Baha, and central Mexico. The Yuma antelope squirrel (A. harrisi) occurs in similar habitat in Arizona and northwestern Mexico.
Chipmunks
The American chipmunk (Tamias striatus) occurs in angiosperm-dominated forest through much of the eastern United States and southeastern Canada. Chipmunks live in burrows that they dig into the ground, and they have large cheek pouches used to carry food into their den.
The western chipmunks (Eutamias spp.) are a more diverse group of about sixteen species occurring through most of North America, especially in the west, as well as in northeastern Asia. The most widespread species is the least chipmunk (Eutamias minimus), a familiar species of a wide range of forest types, and a friendly animal at campgrounds. The yellow pine chipmunk (E. amonoeus) is a widespread western species.
Flying squirrels
There are various types of flying squirrels, especially in tropical forests. However, those of the Americas are two species in the genus Glaucomys. Flying squirrels are nocturnal animals. They nest in cavities in trees, and are proficient at gliding from higher to lower parts of trees, using a wide flap of skin stretching between their legs as their aerodynamic "wings." These animals feed on a variety of seeds, nuts, and fruits, and insects, bird eggs, and fledglings when available. The southern flying squirrel (G. volans) occurs in a wide range of forest types throughout southeastern North America. The northern flying squirrel (G. sabrinus) occurs farther to the north, and ranges across North America.
Resources
books
Banfield, A.W.F. The Mammals of Canada. Toronto, Ontario: University of Toronto Press, 1974.
Barash, D. Marmots Social Behavior and Ecology. Stanford CA: California University Press, 1989.
Hall, E.R. The Mammals of North America. 2nd ed. New York: Wiley & Sons, 1981.
Nowak, R. M. (ed.). Walker's Mammals of the World. 5th ed. Baltimore: Johns Hopkins University Press, 1991.
Wilson, D.E., and D. Reeder. Mammal Species of the World. 2nd ed. Washington, DC: Smithsonian Institution Press, 1993.
Bill Freedman
KEY TERMS
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .- Diurnal
—Refers to animals that are mainly active in the daylight hours.
- Herbivore
—An animal that only eats plant foods.
- Hibernation
—A deep, energy-conserving sleep that some mammals enter while passing the wintertime. In most species, hibernation is characterized by significantly slowed metabolic rates, and sometimes a fall in the core body temperature.
squirrel
squir·rel / ˈskwərl/ • n. an agile tree-dwelling rodent (Sciurus and other genera, family Sciuridae) with a bushy tail, typically feeding on nuts and seeds. ∎ a related rodent of this family (see ground squirrel, flying squirrel). ∎ the fur of the squirrel.• v. (squirreled , squirreling ) 1. [tr.] (squirrel something away) hide money or something of value in a safe place: the money was squirreled away in foreign bank accounts. 2. [intr.] move in an inquisitive and restless manner: they were squirreling around in the woods in search of something.ORIGIN: Middle English: shortening of Old French esquireul, from a diminutive of Latin sciurus, from Greek skiouros, from skia ‘shade’ + oura ‘tail.’ Current verb senses date from the early 20th cent.