Mammals of North America Read online

  ALASKA TINY SHREW Sorex yukonicus (See page 22 for more details)

  This tiny shrew skull has five unicuspids, with the fifth being conspicuous and pigmented. The third unicuspid is larger than the fourth. The other shrew skull this small, the American Pygmy Shrew, has only three unicuspids visible (see page 27).

  ST. LAWRENCE ISLAND SHREW Sorex jacksoni 86-105mm, 32-37mm, 4-5g

  Only shrew on St. Lawrence Island, Alaska. Strikingly colored, like the Pribilof Island Shrew but with slightly darker flanks. Skull has five unicuspids, although the fifth is tiny. Skull is larger than the Pribilof Island Shrew, having a maxillary breadth of at least 4.6mm. Lives in most habitats.

  PLATE 5

  INLAND SOREX WITH SKULLS

  CINEREUS SHREW Sorex cinereus (See page 20 for more details)

  Skull has a series of upper unicuspid teeth showing a gradual reduction in size from front to back.

  AMERICAN PYGMY SHREW Sorex hoyi (See page 20 for more details)

  The third and fifth unicuspid teeth are so tiny that this shrew’S skull appears to have only three unicuspid teeth.

  PRAIRIE SHREW Sorex haydeni 75-100mm, 25-40mm, 2-5g

  Small brown shrew with relatively short tail lacking black tip. Red pigmentation on lower incisor on tip and first two cusps, with more on only the third cusp. Occupies prairie grasslands in the Great Plains, including the Black Hills. Builds bird-like nests under logs and rocks.

  DWARF SHREW Sorex nanus 80-105mm, 25-45mm, 2-3g

  Tiny shrew with pelage back black at base, overlain with grayish brown. Third upper unicuspid smaller than second and fourth; fifth minute. Occurs in arid shortgrass prairies to alpine tundra throughout Rocky Mountain area. Prefers rocky areas such as talus slopes.

  MERRIAM’S SHREW Sorex merriami 90-105mm, 35-40mm, 4-7g

  Small shrew with grayish-brown pelage on back, paler flanks, and whitish underparts. Third upper unicuspid larger than fourth; fifth tiny. No medial tines on incisors. Occurs in sagebrush, grasslands, and woodlands up to 3000m. May use vole runways in grassy areas.

  ARIZONA SHREW Sorex arizonae 80-115mm, 35-55mm, 2-5g

  Slightly larger than Merriam’S Shrew and slightly smaller than Dusky Shrew, with similar coloring. Third unicuspid roughly equal in size to fourth and a small medial tine on upper incisors. Favors forested slopes from 1500-2500m. Active year-round, but more so during periods of rainfall.

  PREBLE’S SHREW Sorex preblei 75-95mm, 30-40mm, 2-4g

  Very small with gray-brown back and silvery belly. Distinguished by medial tine on upper incisors, and the third unicuspid being equal in size to fourth. Among the smallest shrews in North America, it occupies shrub and grasslands, as well as wetter areas at intermediate elevations.

  MT. LYELL SHREW Sorex lyelli 88-108mm, 38-43mm, 4-5g

  Similar to Cinereus Shrew, but restricted to central Sierra Nevada Mountains of California (red area on map). Third unicuspid larger than fourth.

  INYO SHREW Sorex tenellus 85-105mm, 35-50mm, 3-4g

  Slightly larger than Dwarf Shrew, and with relatively longer tail. Grayish-brown pelage above and paler below; sometimes has reddish color on back. Rarely trapped, almost nothing is known about habits. Occurs in semiarid areas and some moist woodlands on mountain ranges in the Great Basin (see yellow area on map of Mt. Lyell Shrew).

  PLATE 6

  COASTAL SOREX WITH SKULLS

  DUSKY SHREW Sorex monticolus 95-140mm, 30-60mm, 4-10g

  Dark brown pelage; medial tine on upper incisors large. Hind feet have more (>4) paired friction pads than Vagrant Shrew. Active all year at all hours. Previously called the Montane Shrew. Widespread and common in a variety of wet habitats.

  ORNATE SHREW Sorex ornatus 80-110mm, 28-46mm, 3-9g

  Small, grayish-brown shrew with medial tine on upper incisors. Fourth unicuspid larger than third. The belly is paler than the back and the skull lacks postmandibular foramina. Body is like Inyo Shrew, but slightly larger and darker. Restricted to Pacific Coastal region of southern California. Favors streamsides with dense vegetation, but also occurs in upland forests (red area on map).

  BAIRD’S SHREW Sorex bairdi 100-145mm, 30-65mm, 5-11g

  Externally like Vagrant Shrew but slightly larger, with a well pigmented medial tine on the upper incisors. Smaller than Marsh Shrew and Fog Shrew; larger than Dusky Shrew. Pelage darker than Pacific Shrew. In winter the pelage is darker brown. Favors moist coniferous forests (see red area on map of Fog Shrew).

  NEW MEXICO SHREW Sorex neomexicanus 103-121mm, 39-54mm, 6-8g

  Like the Dusky Shrew but restricted to Capitan, Manzano and Sandia Mts. in New Mexico. Recently recognized as a unique species based on having a longer unicuspid toothrow and wider space between the two first upper unicuspids than the Dusky Shrew. Known from fir, ponderosa pine, and aspen woodlands (see yellow area on map of Ornate Shrew).

  FOG SHREW Sorex sonomae 105-180mm, 36-85mm, 5-15g

  Largest of the brown shrews found along the Pacific coast. Back color is dark grayish brown, and the upper incisors lack medial tines. Like Pacific Shrew but larger, browner, and with no protuberances on upper incisors. Uses moist areas within coniferous forests (yellow area on map).

  VAGRANT SHREW Sorex vagrans 100-115mm, 38-48mm, 3-8g

  Has small, pigmented medial tines on upper incisors that are usually separated from the pigmented tips by a pale line. Back is brown, sides are paler, and belly is white; tail is bicolored. Prefers moist habitats, frequently in sedges, grasses, and willows along streams and lakes, and in coastal salt marshes.

  PACIFIC SHREW Sorex pacificus 135-155mm, 60-70mm, 10-18g

  Large, pale, reddish-brown shrew. Hind feet with five sets of friction pads. Upper incisors do not have a medial tine, but do have a small protuberance. Prefers moist, dense areas along streams especially in dense vegetation with fallen logs.

  TROWBRIDGE’S SHREW Sorex trowbridgii 104-131mm, 48-59mm, 3-5g

  Small shrew with nearly uniform, dark fur, whitish feet, and bicolored tail. This is the only shrew in its range whose belly is not significantly paler than its back, but does have a strongly bicolored tail. Grayer in winter and browner in summer.

  PLATE 7

  OTHER SHREWS

  NORTH AMERICAN LEAST SHREW Cryptotis parva 61-89mm, 19-37mm, 3-10g

  Tiny shrew with a very short tail (<45% of head and body length). Smaller and browner than other short-tailed shrews in their range. Nests are constructed of grass and leaves in hidden areas, and may contain up to 31 individuals. Occurs in wide variety of habitats, including grassy, weedy, and brushy fields, marshes, and wooded habitats.

  SHORT-TAILED SHREWS - BLARINA - All short-tailed shrews have nearly uniform silver to black fur with brown tips on the hairs. Summer fur is shorter and slightly paler. They are significantly larger and have shorter tails than other shrews in their range. They have a strong and unique smell. The four species of short-tailed shrews are very similar, and most easily identified by geography. The four are identified confidently only by examining chromosome numbers. They are habitat generalists, but are most abundant in moist, well-drained areas.

  NORTHERN SHORT-TAILED SHREW Blarina brevicauda 95-139mm, 17-32mm, 11-30g (Red area on map.)

  ELIOT’S SHORT-TAILED SHREW Blarina hylophaga 92-121mm, 19-25mm, 13-16g (Yellow area on map.)

  SOUTHERN SHORT-TAILED SHREW Blarina carolinensis 72-107mm, 12-26mm, 5-13g (Red area on map.)

  EVERGLADES SHORT-TAILED SHREW Blarina peninsulae 72-107mm, 12-26mm, 5-13g (Yellow area on map.)

  Northern limit between Highland and Leon counties in Florida.

  DESERT SHREW Notiosorex crawfordi 77-98mm, 24-32mm, 3-6g

  Conspicuous ears extend beyond the silvery to brownish-gray fur. Tail short (less than one third of total length) and unicolored. The belly is paler. This is the only shrew in most of the arid and semiarid habitats of the southwestern United States. It builds golf-ball-sized nests of fine fibers inside woodrat houses. Ranges widely in arid environments from sou
thern California eastward to Arkansas (yellow areas on map).

  COCKRUM’S GRAY SHREW Notiosorex cockrumi 77-98mm, 24-32mm, 3-6g

  Identical in appearance to the Desert Shrew. This cryptic species is presently only distinguished through genetic testing. Known from southeast Arizona and Sonora Mexico (red dots on Desert Shrew map), but geographic range may change with more study.

  PLATE 8

  WESTERN MOLES

  MOLES - Moles are tunneling insect-and worm-eaters with tiny eyes. They differ from shrews in having broad forepaws, lacking pigmentation on their teeth, and generally being larger. Compared with the urinary papilla of a female, the penis of a male mole is larger and starts further from the anus. Evidence of their digging in an area can often be seen in the form of tunnels near the surface, and piles of excavated dirt mounded up above tunnel entrances.

  SHREW-MOLE Neurotrichus gibbsii 92-132mm, 12-19mm, 9-11g

  Smallest of the moles, with a short thick tail. Not as well adapted for life underground as other moles, but still mole-like with no external ears, reduced eyes, and slightly broadened forepaws. Forepaws larger than in any shrews. Some of the hairs are longer and coarser than others, making them less velvety looking than other moles. Color ranges from gray to black. Active both day and night, it spends more time above ground than other moles, and frequently makes tunnels through the leaf litter rather than completely underground. Ranges in elevation from sea level to 2500m. Prefers areas with heavy leaf litter, or abundant shrub or bunchgrass cover.

  TOWNSEND’S MOLE Scapanus townsendii 207-237mm, 35-56mm, 100-171g; 183-209mm, 29-51mm, 50-110g

  Larger than all other moles in North America. Hindfoot exceeds 24mm; tail not as hairy as Broad-footed Mole. May form as many as 800 large mounds per hectare in some areas. Exceptionally large mounds contain a large nest chamber 15-20cm below the surface. Constructs both deep and surface tunnels. Feeds mainly on earthworms, insects, and vegetation. Primarily lowland, below 700m, but up to 1900m in Olympic Mountains. Favors deep, loamy soils in meadows and adjacent areas.

  BROAD-FOOTED MOLE Scapanus latimanus 136-193mm, 21-45mm, 39-55g

  Hairiest tail of western moles. The snout is shorter and broader than other moles, and the unicuspid teeth are unevenly spaced. Dark gray fur may have coppery wash. Gradual decrease in size from north to south, with largest individuals in Oregon and smallest in Mexico. Shallow foraging tunnels are constructed near the surface, and deeper, more permanent tunnels are used for resting and nest building. Prefers moist soils from sea level up to 3000m, but also occasionally found among large boulders in drier areas.

  COAST MOLE Scapanus orarius 136-190mm, 30-45mm, 64-91g; 133-168mm, 21-46mm, 61-79g

  The forefoot is broader than it is long, and the hindfoot is less than 24mm long. Evenly spaced unicuspids and scantily haired tail distinguish it from Broad-footed Mole, and it is slightly smaller than Townsend’S Mole. Some individuals have patches of white, cream, yellow, or orange fur on the belly. Mounds of soil deposited on the surface from tunneling activities are slightly smaller than those of Townsend’S Mole. Occurs in coastal sand dunes, grassy meadows, sagebrush grasslands, deciduous forest, and coniferous woodlands.

  PLATE 9

  EASTERN MOLES

  EASTERN MOLE Scalopus aquaticus 103-208mm, 16-38mm, 40-140g; 129-168mm, 20-28mm, 32-90g

  Tail is longer and less hairy than other moles in its range. Foretoes have webbing between them, hence the name “aquaticus.” Although they can swim, they are not aquatic. Three upper and lower premolars on each side. No external ears, and the eyes are completely covered with skin. Northern animals are larger and dark colored; southern animals are golden or silvery colored. Males tend to be larger than females in all areas. Active year-round, and feed on a variety of invertebrates including earthworms and ant larvae. About 99% of their time is spent underground, in tunnels and associated chambers. Construction of roads and golf courses has provided quality soils and increased moisture, allowing spread of Eastern Moles in some areas. Both surface and deeper tunnels are constructed in moist, loamy soils throughout eastern North America.

  HAIRY-TAILED MOLE Parascalops breweri 151-173mm, 26-33mm, 41-63g

  Fleshy tail densely haired, constricted at base, and less than one quarter of total length. Stiff hairs on the snout, behind the eyes, and on the edge of the forefeet are thought to have a tactile function. Snout shorter than that of Eastern Mole, and lacking appendages of Star-nosed Mole. Fur grayish-brownish-black on back; paler and grayish on belly. Young of the year are grayer, with shorter pelage than adults. Tail, feet, and base of snout dark brown, becoming whiter with age. They mate in March-April, and produce a single litter of 4 or 5 young after gestation of 4-6 weeks. Young remain in nest for 4 weeks. Maximum life span is 4 years, and degree of tooth wear can be used to age the animals. Ridges of near-surface tunnels are not as pronounced as those made by the Eastern Mole. Most abundant in light, sandy loams with good cover and sufficient moisture.

  STAR-NOSED MOLE Condylura cristata 132-230mm, 48-99mm, 40-85g

  Unmistakable, snout has 22 fleshy, tentacle-like appendages surrounding the nostrils. Pelage is dense, coarse, and ranges from blackish brown to black, with slightly paler undersides. Tail about as long as head and body, scaly, constricted at base, and covered sparsely with black hair. Most aquatic of the moles, they forage both in the water, and in the usual mole tunnels. They swim by using the enlarged forepaws as paddles. Tunnels are about 3cm in diameter and range in depth from 3 to 60cm. Tails thicken in winter for fat storage. Animals are active year-round and both day and night. They are more active above ground than other moles, although aboveground activity is more common at night. May be gregarious or even possibly colonial. Prefers wet areas, including moist fields, meadows, woods, and marshes.

  PLATE 10

  PIKAS

  PIKAS - These egg-shaped rabbit relatives have small ears and no apparent tail. Our two American species do not overlap in range. Pikas do not hibernate, but survive over winter by hunkering down and eating stored grasses, sedges, weeds, leaves, and other vegetation. Signs of their presence include hay piles in crevices and urine stains on rocks. Emit loud, short, sharp calls for alarm and social purposes. Use talus slopes or areas of broken rocks near meadows.

  COLLARED PIKA Ochotona collaris 178-198mm, 0mm, 117-145g

  Has gray collar, creamy buff facial patch, and white underparts. Upperparts are drab and washed with gray or black. Hindlimbs slightly longer than forelimbs. July juveniles are near adult-size, but are clear gray while adults’ heads and necks are tinged with brown at this time. The fur is long, dense, and soft, and winter pelage is much longer than summer pelage. Active during the daytime, foraging for grasses, which they store in winter caches. Can also be seen sunning on exposed rocks during rest periods. Territorial males accept females in late spring, and 1 or 2 litters of 2-6 blind, naked young are produced after a gestation period of about 30 days. Young reach adult size after 40-50 days, and females breed the following year. Usually found above timberline, but range extends downward to near sea level. Most Pika home ranges include rocky areas for shelter and basking, and adjacent meadows for foraging.

  AMERICAN PIKA Ochotona princeps 162-216mm, 0mm, 121-176g

  Lacks gray collar, has rusty brown facial patch, and buff underparts. Summer pelage ranges from grayish to cinnamon-brown. Winter pelage is grayer and nearly twice as long. Soft gray juveniles mature to adult color by late summer. Easily seen during daylight hours sitting on rocks, surveying surrounding territory. Male and female territories are usually adjacent, and separate except during breeding season. Short vocalizations signal movements to and from territories, and are used as alarm calls as well. Longer calls are used by the males during the breeding season. Both sexes also leave scent marks by rubbing their cheeks on rocks. Females produce two litters of about 3 young per year, but frequently only one litter survives. Maximum longevity is about 6 years. Use talus slopes or areas of broken rocks near meadows.<
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  PLATE 11

  WESTERN COTTONTAILS

  COTTONTAILS - Typical rabbits, often identified by relative ear size. Cottontail identification in some areas may require examination of skull characters. Most active at dusk and dawn.

  MOUNTAIN COTTONTAIL Sylvilagus nuttallii 338-390mm, 30-54mm, 628-687g

  Short, rounded ears are haired on inner surface; whiskers are mostly white. Hind legs are long; feet covered with long, dense hair. Large, grizzled tail is dark above and white below. Associated with sagebrush or timbered areas.

  DESERT COTTONTAIL Sylvilagus audubonii 372-397mm, 45-60mm, 755-1250g

  Large ears are pointed and sparsely haired. Slender feet lack dense hair of other Sylvilagus. Large legs. Whiskers are generally black. Large tail is dark above and white below. Occurs in desert brush, near willows along rivers, or in pinyon-juniper woodlands with shrub cover.

  EASTERN COTTONTAIL Sylvilagus floridanus (See page 42 for more details)