Mammals of North America
Page 5
COYPU Myocastor coypus 86-106cm, 30-43cm, 6.7-9.0kg
A large, brown, aquatic rodent (also known as the Nutria) with a rounded tail. Larger than muskrats and smaller than Beaver. Coarse, brown outer fur covers a softer, denser underfur. Typically burrows into banks, but also eats and rests on small platforms above water in dense vegetation. A nocturnal feeder on aquatic plants, this exotic species can seriously damage wetlands and crops. Introduced from South America for fur farming in Louisiana and Oregon; now widespread in marshes and lakes in much of the south and northwestern United States.
AMERICAN BEAVER Castor canadensis 100-120cm, 23-32cm, 16-30kg
Unmistakable large, aquatic rodent with a sizeable, flat, paddle-shaped, scaly tail. Our largest rodent. Pelage is brown with shiny guard hairs and grayish underfur. Hind feet are webbed. Incisor teeth are large, orange, and ever-growing. Distinctive flattened tail is used as a rudder; also slapped against the top of the water as an alarm. Eats the leaves and inner bark of many tree species, preferring willow and aspen. Survives long, harsh winters by huddling in its insulated lodge, storing fat in its tail, and retrieving and eating underwater food caches. Lives in small family groups. The presence of a Beaver family in an area is easily detected by the saplings and small trees they cut down, strip of bark, and use to build dams and dome-shaped lodges. Typically nocturnal, most often seen around dawn or dusk. Once trapped to extinction in many areas, the Beaver has come back, and is now common in many areas, sometimes considered a pest. Lives in a variety of rivers and lakes.
PLATE 18
MARMOTS
MARMOTS - These large, chunky squirrels have short stubby tails. Because of their terrestrial and diurnal habits, they can be easy to observe. Often leave feces on rocks or logs. All retreat to their burrows for protection, and to hibernate. These vegetarians are typically found near open, grassy habitats.
ALASKA MARMOT Marmota broweri 58-65cm, 15-18cm, 3.0-4.0kg; 54-60cm, 13-16cm, 2.5-3.5kg
A dark marmot with a black nose and top of the head. Tail is short. Typically hibernates September to June. Only marmot in the Brooks mountain range, not known from south of the Yukon river. Found near boulder fields and talus slopes.
YELLOW-BELLIED MARMOT Marmota flaviventris 49-70cm, 15-22cm, 3-5kg; 47-67cm, 13-22cm, 1.6-4.0kg
A small gray marmot with yellow on the belly and neck. There is a white band across the nose. Top of head is black. Hibernates to avoid cold and snow; timing of hibernation depends on age, sex, and local weather. Uses meadows adjacent to talus slopes or rock outcrops.
HOARY MARMOT Marmota caligata 62-85cm, 17-25cm, 5-6kg
A large gray marmot with a relatively long tail. Hairs on the rump are tinged buff. The tail is brownish. Face is marked with white in front of the eyes and a dark band on snout. Dark streaks also mark the side of the head and neck. Typically hibernates from September to May. Alpine-montane specialist except in Alaska where it ranges down to sea level, not known from north of the Yukon river. Lives in treeless meadows where rocky outcrops and talus provide burrows.
OLYMPIC MARMOT Marmota olympus 68-78cm, 19-25cm, 5-7kg
A large, drab brown marmot from the Olympic Peninsula, Washington (yellow area on map). Browner than the Hoary Marmot, but otherwise similar in having a long tail, white nose, and white band in front of the eyes. Coat bleaches yellowish in the summer. Males are larger. Typically hibernates from September to May or June. Prefers montane slopes with rock talus and lush meadows between 1700 and 2000m.
VANCOUVER ISLAND MARMOT Marmota vancouverensis 58-75cm, 16-30cm, 3.0-6.5kg
A dark marmot from British Columbia (see red area on map of Olympic Marmot) with white on the face, chest, and belly. Males are larger. Typically hibernates October to April or May. Endangered because of restricted range. Lives in alpine and subalpine meadows from 1000 to 1460m altitude.
WOODCHUCK Marmota monax 41-67cm, 10-15cm, 3-4kg
A grizzled grayish or brown marmot with reddish-brown underparts. Feet are typically blackish brown, but are pinkish in Alaska. The subspecies M. m. ochracea from northwest Canada and Alaska is reddish cinnamon in color. Males are larger. Widespread and common in meadows and along forest edges.
PLATE 19
EASTERN AND TROPICAL
TREE SQUIRRELS
TREE SQUIRRELS - These familiar diurnal squirrels are grouped by their large bushy tails and tree-climbing habits. Many species have a variety of color morphs.
EASTERN GRAY SQUIRREL Sciurus carolinensis 38-52cm, 15-24cm, 338-750g
A small gray squirrel with a bushy tail edged in white. Belly is whitish. Gray back may have a red-brown tinge. Black-morph individuals and albinos can be quite common in some areas. Makes leaf nests the size of bushel-baskets. Feed on acorns, other nuts, flowers, seeds, buds, bark, and fungi. Abundant, diurnal, and considered game animals in many states. Breeding begins in January-February and a 40-day gestation period results in 1-6 blind, hairless young being born in February and March. The most commonly seen mammal in the eastern United States. Introduced in many western cities. Favors hardwood or mixed forests, including residential areas.
EASTERN FOX SQUIRREL Sciurus niger 45-70cm, 20-33cm, 696-1233g
A large squirrel with a bushy tail edged with brown or orangish brown. Usually twice the size of the Eastern Gray Squirrel, with a more colorful coat and a brownish tinge to the tail. The most typical color phase has rusty-gray upperparts with a rusty-yellow or orange belly. Other color morphs include an all-black form, a southeastern form that is black or dark brown with a white nose and ears, and a gray form with rusty limbs, a black head and a white nose and ears. Makes leaf nests like the Eastern Gray Squirrel. Introduced to some parts of California, Colorado, Oregon, and Washington. Generally abundant, although the subspecies from the eastern shore of Maryland is considered endangered. These savannah animals prefer open, parklike habitats with scattered trees and an open understory.
RED-BELLIED SQUIRREL Sciurus aureogaster 42-57cm, 21-31cm, 375-680g
A colorful squirrel introduced to the Florida Keys in 1938. It is either gray or frosted with white. The underside and sides up to its shoulders are mahogany red. Tail is mixed with black and white. Throughout its range in Latin America, this squirrel is variable in coloration, and black melanistic animals are common. Shy denizen of the treetops. In North America, known only from wooded areas on Elliott, Sand, and Adams Keys.
MEXICAN FOX SQUIRREL Sciurus nayaritensis 49-61cm, 24-30cm, 628-814g
A unique, vividly colored, reddish or orangish squirrel. Dark tail is incredibly bushy and edged in white. Winter pelage has a broad band of blackish hair running down the back; body is yellowish gray, and belly, feet, and eye ring are orangish yellow. In summer the back is a grizzled mixture of pale orangish yellow and black; underparts are tawny. Unlike most tree squirrels, it does not bury nuts or cache foods, as it is primarily a tropical species that barely reaches into the U.S. Frequently spends time foraging on the ground feeding on roots, bulbs, and buds, when acorns and other seeds are unavailable. Inhabits partially open pine-oak forests in the Chiricahua Mountains of Arizona.
PLATE 20
WESTERN TREE SQUIRRELS
ABERT’S SQUIRREL Sciurus aberti 64-58cm, 19-28cm, 540-971g
This squirrel has tufted ears and white on the underside of a broad tail. New ear tufts are grown in October, and may be inconspicuous by summer. The back is gray, with a rusty band. Some animals in central Colorado are uniform brown. North of Grand Canyon, the subspecies S. a. kaibabensis has dark underparts and all-white tail, and was once considered a distinct species. Elsewhere the tail is only white on the underside and the belly is white. The back and belly color are usually separated by a black line. There is also a dark melanistic form. Forages on seeds, buds, and cambium of the ponderosa pine. Small twigs stripped of bark underneath pines are a clear indication of their presence. Conspicuous during the breeding season in spring, when groups of males chase females. Lives chiefly in ponderosa pine forests.
A gray squirrel with a black tail that is washed in white above and marked with an orange or rusty-brown center stripe below. Back and sides are salt-and-peppered steel gray, often mottled with brown or rusty yellow. Underparts are white. Females have only a single litter per year, and average litter size is 3. Although particularly fond of walnuts, they feed on acorns, juniper berries, flowers, buds, and pine seeds. Rarely seen except when they come down to the ground to forage. Shy and secretive, they rarely vocalize, and tend to slip away undetected when disturbed. Uncommon in dense, mature, riparian broadleaf forests of Arizona, New Mexico, and Mexico, primarily in the pine-oak woodland zones of various mountain ranges below the Mogollon rim.
WESTERN GRAY SQUIRREL Sciurus griseus 51-77cm, 24-38cm, 500-950g
Largest native tree squirrel along the Pacific coast, this gray squirrel has a long pepper-gray tail with white edging. Silver-gray back contrasts with pure white belly. A patch behind the ears is pale reddish brown. Feet are dusky. Pelage is more silvery and ears are relatively larger than in the Eastern Gray Squirrel. Forages extensively on the ground for acorns, maple seeds, catkins, green vegetation, and fungi, as well as for pine nuts in the canopy. They scatter-hoard acorns in the fall by making many small holes in the ground. Stick nests, called dreys, are used for rearing young, and tree holes are used as sleeping chambers. Maximum longevity in the wild is 8-10 years. Shy and intolerant of humans, making it difficult to see even though it is diurnal. Threatened in the north of its range. Uses oak-conifer woodlands.
EASTERN GRAY SQUIRREL Sciurus carolinensis
Introduced into some residential areas in the west. Tail is typically browner than the Western Gray Squirrel, lacking any silvery tint. (See page 54 for more details.)
PLATE 21
RED AND FLYING SQUIRRELS
TAMIASCIURUS - Small red, diurnal tree squirrels. Discard pine cones to form middens under favorite perches. Retire in tree holes and ball nests. Give cicada-like buzz call in spring; territorial bark and chatter year-round. A third species lives in Baja California, Mexico.
DOUGLAS’S SQUIRREL Tamiasciurus douglasii 270-350mm, 100-156mm, 141-312g
Less reddish than the Red Squirrel with a gray to orange eye ring and belly. Brownish or reddish-gray sides; there is a chestnut-brown band down middle of back. Black ear tufts and side stripe are more prominent in winter. Uses coniferous and mixed forests.
RED SQUIRREL Tamiasciurus hudsonicus 270-380mm, 90-150mm, 140-250g
Redder than Douglas’S Squirrel with a white eye ring and belly. In summer a distinct black stripe forms between the rusty olive-brown back and white belly. In winter this stripe fades, but other colors are brighter; feet and ventral surface become more gray. Mt. Graham, Arizona, subspecies is Endangered. Common in coniferous forests and southern mixed forests.
FLYING SQUIRRELS - Unique with their large, black eyes and loose flap of skin along sides of body that allows them to glide (not fly) between trees. The two species are separated by geographic range and color of the base of the belly fur. Both have a broad flattened tail that serves as a stabilizer and rudder, as well as a cartilaginous rod extending from the side of their wrist to steer their glides. Both are nocturnal and spend most of their time in the trees. They emit high-pitched squeaks and twitters, nest in tree holes, vine tangles, and nest boxes, sleep in groups in the winter, and eat nuts, berries, fungus, insects, and eggs.
SOUTHERN FLYING SQUIRREL Glaucomys volans 120-140mm, 80-120mm, 46-85g
Hair on the belly is white at both the base and the tip. Back is brown, grayish or tawny; edge of the wing membrane is blackish. Nests are found in tree holes, or constructed of leaves and Spanish moss. Forage in trees and on the ground for lichens, fungi, sap, flowers, buds, bark, seeds, nuts, fruits, and animal matter including insects, birds, mammals, and carrion. Common in low-elevation hardwood forests, less so in mixed and coniferous forests. Also found in parks and wooded residential areas.
NORTHERN FLYING SQUIRREL Glaucomys sabrinus 190-300mm, 90-140mm, 38-123g
Hairs on belly are white at tips but dark gray at base. Otherwise like Southern Flying Squirrel except larger size. Often has pale patches of fur at the base of ears and a dark tail tip. Feed on fungi, fruit, nuts, seeds, small invertebrates, bird eggs, and occasionally on small mammals and birds. Known to visit bird feeding stations. Often common, but Endangered in North Carolina and Virginia. Most common near water in coniferous forests, less in mixed and pure hardwood forests.
PLATE 22
PRAIRIE DOGS
PRAIRIE DOGS - These sandy-colored squirrels live in extensive colonies of underground burrows. Conspicuous with their diurnal feeding and barked alarm calls. All species are vulnerable to human persecution because of an exaggerated and often unwarranted reputation as pests. The four species are distinguished by the color of their back and tail tip.
GUNNISON’S PRAIRIE DOG Cynomys gunnisoni 320-390mm, 40-60mm, 460-1300g; 310-340mm, 50-60mm, 465-750g
Has a gray tail tip with a white border. Head and back are sandy-colored, belly is white. Smallest and least specialized of the prairie dogs, it lives in colonies that are smaller than other prairie dogs, with less modified mounds and more vegetation between holes. Ground-squirrel like in appearance and behavior, with a contact call between individuals that is a raspy chatter. Hibernates from October or November until March or April. Lives in montane valleys and high plateaus in the southern Rockies.
WHITE-TAILED PRAIRIE DOG Cynomys leucurus 350-390mm, 40-70mm, 850-1650g; 320-370mm, 50-60mm, 705-1050g
A buff or gray-colored prairie dog with a white tail tip. Has a dark brown spot above the eye and on the cheek. Contact call between individuals is a laughing bark. Typically hibernates from October to April. Mothers and young pups occupy burrow systems together. Young born in April-May after 30-day gestation period, and emerge during May-June. Males live apart and defend territories, allowing females entry only during the March-April breeding season. Lives in mountain meadows. May venture into semidesert areas in the north of the range.
UTAH PRAIRIE DOG Cynomys parvidens 300-370mm, 50-60mm, 460-1250g; 290-370mm, 50-60mm, 410-790g
A small reddish or cinnamon-colored prairie dog with a white tail tip. Burrow entrances are marked by a mound of dirt. Nest chambers are close to the surface, but they hibernate in winter in deeper chambers, 100-200cm below the surface. Feeds mainly on herbs and grasses. Population densities range from 0.4 to 12 per hectare, depending on habitat condition, but widespread human persecution has driven them out of 90% of their historic range. This endangered species is now limited to grasslands and flat plains in southern Utah.
BLACK-TAILED PRAIRIE DOG Cynomys ludovicianus 360-430mm, 70-90mm, 575-1490g; 340-400mm, 60-90mm, 765-1030g
A large prairie dog with a black tail tip. Contact call between individuals is a “we-oo.” Burrow entrances are surrounded by a large mound of dirt shaped into domes. Dormant in winter, but does not truly hibernate, and can be seen above ground on warm winter days. Clips vegetation very short around colonies for an unobstructed view. Has the most complex social behavior of all prairie dogs. Prior to settlement of the west, very large colonies called “towns” were huge, with the largest estimated to contain 400 million individuals covering 65,000km2. Lives at high densities where not persecuted. Prefers shortgrass to mid-grass prairies.
PLATE 23
LARGE, SPOTTED GROUND SQUIRRELS
LARGE, SPOTTED GROUND SQUIRRELS - These four large, spotted ground squirrels are often conspicuous with their diurnal habits. All put on considerable weight leading up to the late summer or fall start of their hibernation. Coloration and tail size are the key to distinguishing the different species. A recent revision of squirrel taxonomy split these out of Spermophilus and into two new genera.
ROCK SQUIRREL Otospermophilus variegatus 470-500mm, 190-230mm, 450-875g
Has the bushiest tail of any ground squirrel. Back is
typically a buff gray, and is marked with flecks of white; this spotting sometimes producing a wavy striped appearance, but never the white shoulder markings of O. beecheyi. Often has varying amounts of black on the back; this may be across the head, shoulders, back, or entire body. Head varies from pinkish buff to brown. Has conspicuous white crescents above and below the eyes. Tail not as bushy as tree squirrels. Rarely climbs trees. Males are larger. Hibernation is short and intermittent. Typically colonial. Lives in rocky canyons, cliffs, and hillsides.
CALIFORNIA GROUND SQUIRREL Otospermophilus beecheyi 360-500mm, 140-230mm, 350-885g
A large, spotted squirrel with a mantle of light gray running from the ears back onto the shoulders. This gray streak is inconspicuous or absent in some subspecies. Back is brown; dorsal buff flecking is heaviest on rump and flanks. Belly is pale gray. Bushy tail is dark gray above and paler below. Colonial, but each animal has its own entrance to the interconnected burrow system. Hibernates in winter, timing depends on local weather. Common in successional habitat including roadsides, chaparral, and open grassy areas.