Mammals of North America

by Roland W Kays

  SAGEBRUSH VOLE Lemmiscus curtatus 103–142mm, 16–30mm, 17–38g

  Tiny vole with drab buff to ash-gray pelage that is lax, long, and dense. Base of hairs are dark gray. Tail is short, indistinctly bicolored with a dusky line above, and silvery white to buff below. Feet are white or light gray to pale buff, with six plantar tubercles. They have both indistinct surface runways and tunnels under the snow. Nests are in complex burrow systems, or under logs. The diet is strictly limited to green vegetation. Lives in colonies in semi-brushy canyons dominated by sagebrush or rabbit brush mixed with bunchgrass at elevations from 300 to 3700m.

  PLATE 61

  NORTHERN VOLES

  TAIGA VOLE Microtus xanthognathus 152–226mm, 38–53mm, 85–158g

  Large vole with grayish-brown fur and a characteristic yellowish-orange nose, which distinguishes it from the Root Vole. Has small, dark, beadlike eyes, small ears, and short tail. Occurs in riparian, boreal, and sphagnum forest habitats near streams and other moist areas.

  INSULAR VOLE Microtus abbreviatus 136–176mm, 25–32mm, 45–79g

  Large, short-tailed vole from Arctic islands. Nearly identical to Singing Vole, but slightly larger. Adults are brownish dorsally, with pale yellowish sides, rump, tips of ears and face, and a buff-colored belly. Restricted to a few offshore Alaskan islands, where it frequents moist, well-drained lowlands and ryegrass areas of beach ridges.

  SINGING VOLE Microtus miurus 125–168mm, 20–36mm, 22–60g

  Smallish, short-tailed vole. Usually quite buff in color on the flanks and venter, with rather enlarged claws. Differs from other voles in combination of short tail, buff venter, and long claws. In late summer, sits in exposed places and makes a metallic churring sound, hence the name Singing Vole. Often associated with willow in well-drained tundra, and extends up into subalpine and alpine zones.

  EASTERN HEATHER VOLE Phenacomys ungava 122–155mm, 26–41mm, 25–40g

  Small vole with grizzled brown fur with a yellowish wash. The tail is short, and the ears are hardly visible above the fur. Ear tips, nose, and rump are usually more tawny or yellowish than those of other voles. Uses open dry country and especially deciduous shrubby habitat such as willow thickets, poplars, or birch meadows.

  WESTERN HEATHER VOLE Phenacomys intermedius 130–153mm, 26–41mm, 15–41g

  Small, short-tailed vole with long and silky fur that is speckled gray to brownish on the back and paler whitish to silver-gray on underparts. The tail is thin, sparsely haired, and distinctly bicolored (dark gray above, white below). Unique with stiff orange hairs in ears. Whiskers reach the shoulders. Uses boreal habitats including open coniferous forests, riparian areas, and moist alpine and subalpine meadows.

  ROOT VOLE Microtus oeconomus 152–225mm, 30–54mm, 25–80g

  Medium-sized for genus with short ears and a short tail. Upper parts range from dusky gray through rich buff to tawny, cinnamon brown, or rusty brown. All color morphs have a mixture of black-tipped hairs. Sides are paler, and underside is white, sometimes washed with dark buff. Tail is bicolored. Larger than Singing Vole, and has broader skull. Slightly larger than Meadow Vole, and lacks rounded posterior loop on second upper molar. Uses moist mountain meadows of the Arctic tundra, especially near streams, lakes, and marshes.

  PLATE 62

  TYPICAL VOLES

  MEXICAN VOLE Microtus mexicanus 123–144mm, 25–34mm, 18–42g

  Small vole with grizzled cinnamon-brown upperparts and buff to cinnamon underparts. Relatively short tail distinguishes it from Meadow Vole and Long-tailed Vole. Females have only four mammae, rather than six or eight as in Prairie Vole and some other voles. Belly is tannish rather than whitish as in Montane Vole. Litter size is low for voles, averaging 2.4. Diet is strictly green leaves and stems of grass. Presence can be detected by runways through the grass, which connect feeding areas with burrow systems. Normally found in grassy meadows in coniferous forests, but occupies drier habitats than most other voles.

  PRAIRIE VOLE Microtus ochrogaster 130–172mm, 24–41mm, 37–48g

  Small vole with long, coarse fur that is grizzled grayish brown from hairs with black and brownish-yellow tips. Sides are slightly paler. Belly is a neutral gray or is washed with whitish or pale cinnamon. Tail is strongly bicolored, and longer than that of Woodland Vole and Southern Bog Lemming. Differs from Meadow Vole in having shorter tail, five toe pads, coarser fur, and venter without silver-tipped hairs. Population size can be judged by the number of runways, both aboveground and underground. Can be active anytime, but more nocturnal in hot summertime. Occurs in all types of prairie habitats, plus agricultural areas such as fencerows and fallow fields.

  BEACH VOLE Microtus breweri 165–215mm, 35–60mm, 45–63g

  An insular offshoot of the Meadow Vole, the Beach Vole is slightly larger, paler, and more grizzled. Frequently has a white blaze on forehead or elsewhere on face. Nests are built aboveground in beach grass and underground in sandy soil. Has small litters (3 or 4), longer life span (13 weeks), better parental care, and is less aggressive than the Meadow Vole. The breeding season is April–October, the gestation period is 3 weeks and lactation lasts 2 weeks. Breeding is continuous and females can produce a litter every 3 weeks if conditions are good. Limited to Muskeget Island, Massachusetts, where it prefers beach grass stands.

  MEADOW VOLE Microtus pennsylvanicus 140–195mm, 33–64mm, 33–65g

  A robust vole with a relatively short tail and compressed muzzle. Dull brown above with a gray belly. Immatures slightly darker than adults. Winter pelage is thicker and finer than the sparser, coarser summer coat. Distinguished from other voles by unique dental characters: five closed triangles on first lower molar, three transverse loops and no triangles on third lower molar, four closed triangles with a posterior loop on second upper molar, and three closed triangles on third upper molar. The subspecies M. p. dukecampbelli known only from Cedar Key, Florida, is Endangered. This is the most prolific mammal on Earth, and occupies moist grassy fields and meadows over much of northern North America.

  PLATE 63

  EASTERN VOLES AND BOG LEMMINGS

  WOODLAND VOLE Microtus pinetorum 111–139mm, 12–29mm, 14–37g

  Tiny reddish vole with reduced eyes and ears and large foreclaws for its semifossorial life. Tail is short and facial vibrissae are well developed. Fine fur is chestnut-colored above and on the sides and paler gray or silvery below. Tail is bicolored, but colors grade gently and no sharp distinct line is noticeable, distinguishing it from other reddish voles. Whiskers are well developed. Incisors are not grooved. They build underground runways and burrows with nest chambers lined with dried leaves and grasses. Common in eastern forests with good litter cover or grassy areas.

  ROCK VOLE Microtus chrotorrhinus 140–185mm, 42–64mm, 30–48g

  Medium-sized vole with yellowish-orange or pale yellowish wash on snout, and occasionally on rump as well. Smaller than the otherwise similar Taiga Vole, which occurs only to the northwest of the Rock Vole. Breeding season is March–October, and litters of 3–6 are produced regularly, as the females breed again immediately after giving birth. Feeds extensively on bunchberry, and their presence can be detected by the accumulation of cut vegetation that they cache under flat rocks along streams. Uses hardwoods and mixed deciduous coniferous forests with rocks, frequently near streams or other water sources.

  BOG LEMMINGS-SYNAPTOMYS- Smaller than voles, but with a relatively large head and facial hairs surrounding the snout, which can be erected to make the face appear larger than it really is. Although the head is relatively large, the rostrum is short. Both have grooved incisors, which are sharper in S.borealis.

  SOUTHERN BOG LEMMING Synaptomys cooperi 94–154mm, 13–24mm, 21–50g

  Similar to S.borealis, but with dark brown above and pale gray on underside. Also has six mammae instead of eight, as in S.borealis. Active throughout the year, mostly at dawn and dusk, but forages throughout the night and less during the day in the hotter months. They make runways similar
to other voles in grassy habitats. Occurs in a wide variety of habitats including clearings in woodlands, grasslands, mixed deciduous/coniferous woodlands, spruce-fir forests, and freshwater wetlands.

  NORTHERN BOG LEMMING Synaptomys borealis 110–140mm, 17–27mm, 27–35g

  Small lemming with grizzled gray to brown pelage on the back and pale gray underneath. Fur has a coarse, ruffled appearance and the short tail is bicolored. Distinguished from S. cooperi by having buff-colored hairs at base of the ears, sharper incisors, and more mammae. Unlike most voles, population sizes are usually low. Occurs in a variety of habitats that are wet with many sedges and grasses including spruce-fir forests, wet meadows, sphagnum bogs, and alpine tundra.

  PLATE 64

  NORTHERN LEMMINGS

  NORTHERN LEMMINGS - In good years, their populations can explode and large numbers of animals can be seen running across the low tundra, dispersing out of overpopulated areas. This has led to the myth of suicidal, cliff-jumping lemmings. Most Dicrostonyx lemmings have a seasonal molt from summer brown to winter white coat and a unique bifurcated claw on the forefeet for digging through snow.

  NEARCTIC BROWN LEMMING Lemmus trimucronatus 130–180mm, 18–26mm, 45–130g

  A brown northern lemming, without stripes or collars. Relatively large with tawny brown to cinnamon on backs and sides. Has a shorter tail than bog lemmings or voles. Uses subalpine tundra above timberline.

  UNGAVA COLLARED LEMMING Dicrostonyx hudsonius 125–166mm, 12–16mm, 35–85g

  Only striped and collared lemming in eastern Canada. Distinguished from Nearctic Collared Lemmings in summer by having a dull reddish patch of hair around the ears, and in having browner (less steel-gray) pelage. Found in tundra habitats, including rocky hillsides and alpine meadows (red area on map).

  RICHARDSON’S COLLARED LEMMING Dicrostonyx richardsoni 115–150mm, 9–15mm, 35–90g

  A brownish collared lemming. Younger animals have a thin black stripe on back from tip of nose to base of tail. Nearctic Collared Lemmings tend to be more grayish. Occupies tundra habitats (yellow area on map of Ungava Collared Lemming).

  NEARCTIC COLLARED LEMMING Dicrostonyx groenlandicus 110–177mm, 10–20mm, 30–50g

  A grayish collared lemming. Summer coat is grayish-buff to dark gray, with aspects of buff to reddish brown above. Richardson’s Collared Lemmings are darker reddish brown. Occurs only on Arctic tundra.

  NELSON’S COLLARED LEMMING Dicrostonyx nelsoni 108–142mm, 11–21mm, 45–55g

  Superficially similar to Ungava Collared Lemming and much smaller than Unalaska Collared Lemming. Dorsal stripe variable from distinct to indistinct (red area on map).

  OGILVIE MOUNTAINS COLLARED LEMMING Dicrostonyx nunatakensis 128–130mm, 11–13mm, 35–45g

  An endemic lemming known only from the Ogilvie Mts in the Yukon Territory (not illustrated). Pale gray-brown back and no reddish rump contrasts with nearby Nearctic Collared. Uses rocky alpine tundra at base of a glacial cirque (yellow area on map of Nelson’s Collared Lemming).

  UNALASKA COLLARED LEMMING Dicrostonyx unalascensis 130–165mm, 11–18mm, 50–60g

  Only lemming on Umnak and Unalaska isles of the Aleutian Archipelago, Alaska (not illustrated). Like Nearctic Collared Lemming, but larger and does not turn white or develop winter digging claws. Pelage is soft and medium rusty brown with a distinctive mid-dorsal stripe.

  PLATE 65

  GHOST AND LEAF-NOSED BATS

  PETERS’S GHOST-FACED BAT Mormoops megalophylla 73–98mm, 20–28mm, 15–16g

  Bizarre-looking face with wartlike protuberances on nose and leaflike appendages on chin. Dorsal fur long and lax, with each hair containing four different color zones, the second of which tends to be reddish in mature adults. Forearm 46–56mm. Widely distributed in riparian zones in arid lands up to 3000m.

  CALIFORNIAN LEAF-NOSED BAT Macrotus californicus 85–99mm, 28–41mm, 12–22g

  Long ears (more than 25mm), gray fur, and a distinct, leaflike appendage on the tip of the nose. Tail extends slightly beyond edge of tail membrane. Forearm 46–55mm. May form colonies ranging in size from a few individuals to over 1000. Found in Lower Sonoran lifezones.

  MEXICAN LONG-TONGUED BAT Choeronycteris mexicana 81–103mm, 6–10mm, 10–25g

  Medium-sized leaf-nosed bat with grayish to brownish fur, an elongated muzzle, and a prominent nose leaf. Similar to long-nosed bats, but has a well-developed tail membrane, enclosing a short, conspicuous tail. Forearm 43–49mm. Lacks lower incisors. Forms small colonies in caves, mine tunnels, buildings, and culverts.

  MEXICAN LONG-NOSED BAT Leptonycteris nivalis 76–88mm, no tail, 18–30g

  The only leaf-nosed bat occurring in Texas, this species may overlap with the Lesser Long-nosed Bat in New Mexico, where it differs by being larger, with grayish fur, a wider tail membrane and shorter wings. Forearm 56–60mm. Emory Peak Cave in Big Bend National Park has housed as many as 10,000 of these bats in mid-summer. The Mexican Long-nosed Bat is classified as an Endangered species; its migratory movements, specialized feeding, and roosting habits make it a conservation risk.

  LESSER LONG-NOSED BAT Leptonycteris yerbabuenae 75–85mm, no tail, 15–25g

  Lack of tail distinguishes this species from the Californian Leaf-nosed and Mexican Long-tongued bats. Forearm 51–54mm. Summer migrant into southern Arizona and New Mexico, this species occasionally visits hummingbird feeders in search of nectar. The Lesser Long-nosed Bat is classified as an Endangered species; its migratory movements, specialized feeding, and roosting habits make it a conservation risk.

  HAIRY-LEGGED VAMPIRE BAT Diphylla ecaudata 67–93mm, no tail, 24–43g

  This rare bat has a nose leaf that is greatly reduced and no tail. The incisors are prominent, with very sharp cutting edges. Fur on the back is dark brown, and the belly is slightly paler. Forearm 50–56mm. Normally roosts solitarily in caves or mine tunnels. This species only eats blood, and specializes in feeding on roosting birds. Known in the United States only by a single specimen from Val Verde County, Texas.

  PLATE 66

  MOLOSSID BATS

  FREE-TAILED BATS - This family of bats, the Molossidae, is distinguished by having a tail that extends well beyond the terminal edge of the tail membrane. Their unique large ears are an adaptation for the echolocation of insect prey in their high-altitude, high-speed hunts.

  MEXICAN FREE-TAILED BAT Tadarida brasiliensis 85–109mm, 30–39mm, 10–15g

  The most common member of the family has deeply furrowed lips, and ears that are not joined at the midline. Forearm 36–46mm. It forms summer nursery colonies of millions of individuals in large caves.

  POCKETED FREE-TAILED BAT Nyctinomops femorosaccus 99–118mm, 34–45mm, 14–17g

  Similar to Mexican Free-tailed Bat, but differs in having ears joined at the base. Forearm 45–50mm. Can be found near large, open-water sources.

  BIG FREE-TAILED BAT Nyctinomops macrotis 120–160mm, 40–57mm, 22–30g

  Large bat with wrinkled lips. Upperparts range from pale reddish brown to almost black, but individual hairs are white at the base. Large ears are joined at the base. Forearm 58–64mm. Inhabits rugged, rocky canyoncountry in southwestern United States.

  GREATER BONNETED BAT Eumops perotis 159–187mm, 55–72mm, 45–73g

  The largest bat in North America is darker than Underwood’s Bonneted Bat, and lacks long guard hairs on the rump. Forearm 72–83mm. Males have a well-developed throat gland that emits a thick, smelly musk in the breeding season. Roosts in cliffside crevices in rugged canyonlands of the arid southwest.

  UNDERWOOD’S BONNETED BAT Eumops underwoodi 160–165mm, 50–64mm, 40–65g

  Large bat with slightly shorter ears than the Greater Bonneted Bat, and has a distinctive fringe of bristle-like guard hairs on the rump. Forearm 65–77mm. They are known only from extreme southern Arizona and Mexico.

  FLORIDA BONNETED BAT Eumops floridanus 123–165mm, 40–64mm, 25–47g; 117–156mm, 40–61mm, 28–55g

  Medium-sized free
-tailed bat with smooth lips and large ears that are joined at the base. Forearm 55–68mm. No other similar-sized free-tailed bats occur in its southern Florida range. Favors old, mature trees as roosting sites, but will use buildings (see red area on map).

  PALLAS’S MASTIFF BAT Molossus molossus 89–104mm, 30–39mm, 10–14g

  Small free-tailed bat with dark brown or grayish-brown fur. Individual hairs are white at their base. Short bristles on rump and wrinkles on the upper lip. Forearm 36–40mm. Tends to roost in attics. Limited to a few colonies roosting in buildings on the Florida keys (see yellow area on map for Florida Bonneted Bat).

  PLATE 67

  LASIURINE BATS

  TREE BATS - Migratory bats, common throughout the United States in the spring and fall, and widely distributed across North America in the summer. They tend to be solitary, and roost in trees and foliage rather than caves.