COLUMBIAN GROUND SQUIRREL Urocitellus columbianus 320-410mm, 80-120mm, 340-812g
A large ground squirrel with a reddish-brown nose and forelegs. Back is grayish with indistinct buff spotting. Bushy tail is reddish and edged with white and some black hairs. Hibernates for more than two thirds of the year. Males emerge first, and breeding begins when females emerge in early spring. Males first breed at age 3, and females in their second year. Both sexes are territorial. Food items include fruit, bulbs, seeds, and flowers as well as occasional insects and carrion. Lives in colonies in alpine meadows and grassy lowlands.
ARCTIC GROUND SQUIRREL Urocitellus parryii 330-490mm, 80-150mm, 530-816g
Unique with reddish-brown back that is flecked with whitish spots. Spring-summer pelage is reddish-brown while fall-winter fur is grayish, with a cinnamon-brown head color. Males are larger. Both sexes get much heavier just before hibernation. Northernmost ground squirrel, it hibernates for seven winter months. Feed on leaves, seeds, and berries as well as carrion and insects. Burrows are limited to areas where permafrost is below 1m, allowing for deep tunnels. Alarm calls include a shrill whistle or sharp “cheek-chick” call. Found in tundra and mountain meadows above the timberline.
PLATE 24
BUSHY-TAILED, FLECKED GROUND SQUIRRELS
BUSHY-TAILED, FLECKED GROUND SQUIRRELS - These large ground squirrels have pale flecks on their back that do not form distinct spots. The color and size of their tail distinguishes the different species. All are diurnal seed and leaf eaters. A recent revision of squirrel taxonomy split these out of Spermophilus and into two new genera.
FRANKLIN’S GROUND SQUIRREL Poliocitellus franklinii 355-410mm, 120-158mm, 340-950g
A large ground squirrel with a gray head and a long, gray, bushy tail. Underparts dull whitish or buff. Body and ears are smaller than the tree squirrels. Gives loud whistle alarms and musical trills. Hibernates AugustSeptember until April-May. Colonies in a variety of habitats including tall grass, shrub land, and woodland edge.
BELDING’S GROUND SQUIRREL Urocitellus beldingi 270-315mm, 60-75mm, 300-450g; 265-295mm, 60-75mm, 230-400g
Tail is moderately bushy, reddish, and black-tipped. There is a broad, brown band that runs down the center of the back, contrasting slightly with the grayish sides. Has a narrow, white eye ring. Extensive hibernator, so that all foraging, growth and reproduction occurs in three frantic spring and summer months. Typical alarm call is a trill of 5-8 short whistles. Uses short grass habitats in alpine meadows, along roadsides, and in cultivated fields.
UINTA GROUND SQUIRREL Urocitellus armatus 270-320mm, 43-81mm, 250-600g
Uniform speckled brownish or grayish back with a grayish undertail. Head and neck are always gray, back varies from grayish to brownish to cinnamon-buff. Not as buff as the Wyoming Ground Squirrel, with gray (not buff) under the tail. Larger than the Piute Ground Squirrel, with a longer tail. Gives a variety of calls including chips, churrs, and squeals. Uses sagebrush, grassy meadows, and sometimes cultivated lawns.
WYOMING GROUND SQUIRREL Urocitellus elegans 253-307mm, 59-79mm, 286-411g
A flecked, drab-colored ground squirrel with a buff undertail. Flecks may be pale pinkish buff, clay-colored, or pinkish cinnamon. Underparts are cinnamon and gray-colored. Distinguished from the similar Belding’S and Uinta ground squirrels by having a buff (not reddish or grayish) underside of the tail with a white edging. Churr and chip calls are higher pitched than in Richardson’S Ground Squirrel. Uses mountain meadows above 1500m and talus slopes above the timberline.
RICHARDSON’S GROUND SQUIRREL Urocitellus richardsonii 283-337mm, 65-88mm, 290-745g; 264-318mm, 55-82mm, 120-590g
A flecked, drab ground squirrel with a white-edged tail. Gray fur is washed with cinnamon buff above and pale buff or white below. Tail is bordered by white, and clay-colored or light brown below. Distinguished from the similar Belding’S and Uinta ground squirrels by having a brownish (not reddish or grayish) underside of the tail with a white edging. Churr and chip calls are lower pitched than in Wyoming Ground Squirrel. Hibernates from September to March.
PLATE 25
THIN-TAILED, UNMARKED GROUND SQUIRRELS
THIN-TAILED, UNMARKED GROUND SQUIRRELS - Small squirrels with plain backs without flecks or spotting. Color and size of their thin tails distinguish species. Like other ground squirrels, they are diurnal leaf and grain eaters that retire to burrow systems. Recently recognized as being part of a new genus.
ROUND-TAILED GROUND SQUIRREL Xerospermophilus tereticaudus 202-278mm, 60-112mm, 110-170g
This small squirrel has whitish cheeks, and a darker top of the head. Undertail is buff or cinnamon. Pelage is plain, and two distinct color morphs are known with the back being either cinnamon or drab gray-brown. Sides of head are dull white. Belly is white. Smaller than the Mohave Ground Squirrel with white cheeks and a buff undertail. Has a thinner tail than other ground squirrels, and no spots or flecking. Does not hibernate, but may enter torpor in the winter. Call with high-pitched whistles or peeps. Uses sandy flat areas in the Sonoran and Mohave deserts.
MOHAVE GROUND SQUIRREL Xerospermophilus mohavensis 210-230mm, 57-72mm, 70-300g
A small spotless squirrel with brownish cheeks and a white undertail. Tail has short hairs and is creamy white underneath. Larger than the Round-tailed Ground Squirrel with a shorter tail that has a white (not buff or cinnamon) undersurface, and brown cheeks. Has a thinner tail than other ground squirrels, and no spots or flecking. Often holds tail over back to display the creamy white underside. Hibernates in winter. Uses level sandy areas with sparse shrub growth in the Mohave Desert.
UROCITELLUS TOWNSENDII SPECIES GROUP - Small squirrels with short ears and unmarked pelage. Color is grayish washed with pinkish buff above and buff-white below. The sides of the head and hind legs are tinted with reddish buff. Underside of tail is light cinnamon. In addition to geographic range, they can be distinguished from other ground squirrels by their lack of flecking, and thin tail. These three species were originally considered conspecific, and were only recently split by genetic studies. There are no known morphological differences to distinguish them.
TOWNSEND’S GROUND SQUIRREL Urocitellus townsendii 200-232mm, 39-54mm, 125-325g
Has 36 chromosomes. Hibernates from June till February. Uses sagebrush and agricultural areas north of the Columbia River and south of the Yakima River (red area on map).
MERRIAM’S GROUND SQUIRREL Urocitellus canus 190-217mm, 37-42mm, 100-250g
Has 46 chromosomes. Hibernates from August till March. Uses grasslands and pastures with big sagebrush and western juniper (see yellow area on map of Townsend’S Ground Squirrel).
PIUTE GROUND SQUIRREL Urocitellus mollis 201-233mm, 44-61mm, 84-205g
Has 38 chromosomes. Hibernates for most of winter. Uses agricultural areas and desert communities.
PLATE 26
SMALL, SPOTTED GROUND SQUIRRELS
SMALL, SPOTTED GROUND SQUIRRELS - These five small ground squirrels all have spots that are more distinct than the diffuse speckling sometimes found in “unspotted” ground squirrels. All are diurnal. Typically leaf and seed eaters, most will also eat insects when they are abundant.
THIRTEEN-LINED GROUND SQUIRREL Ictidomys tridecemlineatus 170-310mm, 60-132mm, 110-270g
Back is marked with 13 alternating stripes that are either solid pale or dashed and dark. Tail and back are mixed brown and white. Has a white eye ring. Heaviest just before hibernation in September and October. Emerges from hibernation in March or April. Rarely ventures far from escape burrow. Warning call is a soft, trilled whistle. Often seen standing upright on a roadside or other mowed area
MEXICAN GROUND SQUIRREL Ictidomys parvidens 280-380mm, 110-166mm, 137-330g
Has nine rows of squarish white spots on its brown back. Larger than I. tridecemlineatus with no solid white stripes. Belly is whitish or buff. Tail is moderately bushy. Head is brown, tip of nose is often cinnamon or yellowish. Has a white eye ring. Males are larger. Norther
n populations hibernate. Previously known as Spermophilus mexicanus. Lives alone or in colonies in grassy habitats or arid areas with brushy vegetation.
SPOTTED GROUND SQUIRREL Xerospermophilus spilosoma 185-253mm, 55-92mm, 100-200g
A small, drab ground squirrel with light spotting and a bushy tail. Some populations are more spotted than others. Short round tail is dark, with a black tip and a cinnamon underside. Belly is light-colored. Color of back is variable and blends in with the local substrate including: cinnamon drab, smoke gray, and brownish morphs. Northern populations hibernate from July-Sept to April. Use desert scrublands and grasslands.
WASHINGTON GROUND SQUIRREL Urocitellus washingtoni 185-245mm, 32-65mm, 120-300g
A small, brownish-gray squirrel with distinct whitish spots. Found only in Washington and Oregon (yellow area on map). Grayish-white color on the belly and sides changes abruptly to the darker dorsal color, forming a lateral line between the two colors. Underside of tail, nose, and lower legs are pinkish cinnamon (not rufous as in the Idaho Ground Squirrel). Also has smaller ears (10-13mm). Extensive hibernators, typically only active above ground from late February to early summer. Threatened by hunting and habitat destruction. Uses dry open sagebrush or grassland habitat.
IDAHO GROUND SQUIRREL Urocitellus brunneus 209-258mm, 39-62mm, 120-290g
A small, lightly spotted squirrel with russet-colored legs, nose, and tail. Only found in Idaho (see red area on map of Washington Ground Squirrel). The two known subspecies can be distinguished, and may actually be different species. U. b. brunneus from Adams and Valley counties is reddish gray with a buff-white eye ring. U. b. endemicus, from Gem, Payette, and Washington counties is grayish brown with a creamy white eye ring and russet on the legs and base of tail. Lives in burrow systems dug in select mountain meadows.
PLATE 27
STRIPY GROUND SQUIRRELS
ANTELOPE SQUIRRELS - These small, striped squirrels are recognized by their single pair of white stripes that run from shoulder to rump. Unlike chipmunks, they have no facial stripes. They often carry their tail arched forward over their back. All are diurnal and call with long, high-pitched trills.
HARRIS’S ANTELOPE SQUIRREL Ammospermophilus harrisii 216-267mm, 67-92mm, 113-150g
Underside of tail is grayish from mixing of black and white hairs. Back is pale brown to blackish. Eye ring and belly are whitish. Often sits erect on hind feet. Runs with tail held vertically. Burrows under shrubs in a variety of desert habitats.
TEXAS ANTELOPE SQUIRREL Ammospermophilus interpres 220-235mm, 68-84mm, 99-122g
Underside of tail is white with two dark bands. Back and basal third of tail is gray. Last two thirds of tail is grayish black. Shoulders, hips, and outer legs are yellowish brown. Belly is white. Uses rocky and shrubby areas around desert mountain ranges.
WHITE-TAILED ANTELOPE SQUIRREL Ammospermophilus leucurus 188-239mm, 42-87mm, 96-117g
Underside of tail is white with one dark band. Subspecies vary from grayish brown to cinnamon. Fur is longer and grayer in winter. Uses a variety of shrubby desert habitats.
NELSON’S ANTELOPE SQUIRREL Ammospermophilus nelsoni 230-267mm, 67-78mm, 142-179g
Coloration is generally buff rather than gray. Underside of tail is creamy white. Upperparts are a dull yellow-brown and underparts and eye ring are whitish. Only antelope squirrel in range. Inhabits gentle slopes with shrubby cover.
GOLDEN-MANTLED GROUND SQUIRRELS - Their conspicuous light and dark side stripes and colorful heads identify these two small ground squirrels. They are larger than chipmunks and lack face stripes. The two species are distinguished by range and the distinctiveness of their colorful hood. Recently placed in their own genus.
GOLDEN-MANTLED GROUND SQUIRREL Callospermophilus lateralis 245-295mm, 70-120mm, 175-350g
A small ground squirrel with a dorsal stripe and well defined golden hood. Head and neck may be golden brown, tawny, or russet-colored. Winter pelage is grayer. Does not overlap (yellow area on map) with the larger Cascade Golden-mantled Ground Squirrel.
CASCADE GOLDEN-MANTLED GROUND SQUIRREL Callospermophilus saturatus 286-315mm, 92-118mm, 200-300g
Small ground squirrel with a dorsal stripe and poorly defined russet hood. Sometimes considered subspecies of Golden-mantled Ground Squirrel (see red area on map of Golden-mantled).
PLATE 28
EASTERN AND ROCKY MOUNTAIN CHIPMUNKS
CHIPMUNKS - This group of small, striped squirrels is easy to recognize, but it is very difficult to distinguish between the 22 different species. Easterners have it easy, with only one to choose from. Western naturalists should consider geographic range and subtle color differences. The Eastern Chipmunk hibernates in the winter while western species rely on underground stores of fruits and seeds to survive the winter.
LEAST CHIPMUNK Tamias minimus 185-216mm, 78-113mm, 32-50g
A very small chipmunk. The subspecies T. m. silvaticus shows coloration typical of many central and northern forms. The subspecies T. m. scrutator from far western United States has gray on the rump, central dorsal stripe, and head. Southwestern forms are paler brown (see page 74). Runs with tail held vertically. Typically flicks tail up and down when perched. Calls short and infrequent. Most abundant in coniferous forests and tundra, also found in woodlands, meadows, scrublands, and sagebrush desert.
EASTERN CHIPMUNK Tamias striatus 215-285mm, 80-115mm, 80-150g
This red-rumped rodent is the only chipmunk in most of eastern North America. Our largest chipmunk. Color of back varies from pale brown in southern Ontario, to dark red Appalachian forms, and brightly colored animals in the southwest of their range. Vocalizes with a series of chips and a high-pitched alarm call. Common in eastern deciduous forests.
CLIFF CHIPMUNK Tamias dorsalis
T. d. utahensis from Utah has a more distinct dark stripe down the center of its back than other subspecies. Identifiable by pale gray color of back. (For more details, see page 74.)
RED-TAILED CHIPMUNK Tamias ruficaudus 223-248mm, 100-121mm, 53-62g
Has a long tail that is red on the underside. Winter form is paler, but still has red tail. Some suggest that the northern subspecies T. r. simulans should be elevated to full species based on the morphology of their genital bones. Common in dense coniferous forests.
YELLOW-PINE CHIPMUNK Tamias amoenus 186-238mm, 72-109mm, 36-50g
A mid-sized, yellowish chipmunk. Larger than the Alpine and Least chipmunks, smaller than other chipmunks. Has brighter colors than the Least Chipmunk, with a reddish (not yellowish) undertail. Common in chaparral, meadows, and rocky outcrops.
UINTA CHIPMUNK Tamias umbrinus 210-240mm, 84-119mm, 51-74g
A brownish chipmunk with brown and white dorsal stripes. Difficult to distinguish by sight. Some consider it conspecific with Palmer’S Chipmunk. Has less red than the Panamint Chipmunk and is larger than the Least or Yellow-pine chipmunks. Holds tail horizontal when running. Has five-syllable call. Common in montane coniferous forests, especially above 1830m.
PLATE 29
SOUTHWEST CHIPMUNKS
GRAY-COLLARED CHIPMUNK Tamias cinereicollis 208-242mm, 90-109mm, 55-70g
Prominently marked with gray on the cheeks, shoulders and rump. Dorsal stripes are darker than those of the Gray-footed Chipmunk. Hind feet are pinkish buff. In winter the flanks and tail edges are paler, and the belly has more gray. Runs with tail held horizontally. Often sits on logs slowly waving tail from side to side while “chucking.” Alarm call is a shrill “chipper.” Climbs trees more than other chipmunks. Has a limited range in montane coniferous forests between 1950 and 3440m.
GRAY-FOOTED CHIPMUNK Tamias canipes 210-264mm, 91-115mm, 65-75g
Hind feet are gray on the dorsal surface. Stripes on back are a dark rusty color (not with a solid black center like the Gray-collared Chipmunk). Has a grayer head than the Colorado Chipmunk, with gray (not orange) shoulders. Females are slightly larger. Vocalizes from hiding spots with a light “chipper” or a low repeated “chuck.” Most ac
tive at dawn on rocky slopes with thick brush.
CLIFF CHIPMUNK Tamias dorsalis 204-226mm, 82-100mm, 54-64g; 212-235mm, 89-105mm, 58-67g
Gray back has indistinct stripes. Center dorsal stripe dark, others faint. White patch behind ears. Sides are brownish, underparts are creamy white. Tail is brownish orange below. Call is a series of chips with a terminal pulse. Common in a variety of habitats with cliffs or boulders. (For Utah form, see page 72.)
LEAST CHIPMUNK Tamias minimus
The southwestern subspecies are paler than those in the Rockies. Distinguished from other southwestern chipmunks by small size, dull color, and lack of gray. Runs with tail held vertically, often flicks tail up and down. (For more details, see page 72.)
COLORADO CHIPMUNK Tamias quadrivittatus 212-245mm, 80-118mm, 54-80g
Has bright, contrasting stripes, a grayish forehead, and orangish shoulders. T. q. australis from southern Arizona has some gray on shoulders, but is distinguished from the Gray-collared Chipmunk by being smaller and having an orange wash on shoulder. T. q. quadrivittatus from northern Arizona, Utah, and Colorado has brighter orange flanks than the similar Uinta Chipmunk, with more red on the tail underside and darker dorsal stripes that extend all the way to the base of the tail. Uses rocky slopes in ponderosa pine forests.
Mammals of North America Page 6
