Mammals of North America

by Roland W Kays

  EASTERN RED BAT Lasiurus borealis 95–l26mm, 45–62mm, 7–l6g

  A distinctive looking bat with mottled reddish and grayish pelage that extends well over the interfemoral membrane. The ears are low and rounded; tragus is short and blunt. Red bats have a small projection known as a “lacrimal shelf” at the back of the skull. Forearm 37–42mm (yellow area on map).

  WESTERN RED BAT Lasiurus blossevillii 92–112mm, 44–52mm, 6–10g

  (Not pictured) Recently split from the Eastern Red Bat by genetic data, these two are best distinguished by range (see red area on map of Eastern Red Bat). The Western species differs in being slightly smaller, with fewer frosted hairs on the back and tail membrane.

  SEMINOLE BAT Lasiurus seminolus 89–114mm, 35–50mm, 9–14g

  Similar to female Eastern Red Bats, this species has broadly rounded ears, long pointed wings, and a densely furred interfemoral membrane. Forearm 37–43mm. Favors Spanish moss as a day roost.

  NORTHERN YELLOW BAT Lasiurus intermedius 121–164mm, 51–77mm, 14–20g

  Distinguished by yellowish-gray or yellowish-brown pelage, which extends only onto the basal half of the tail membrane. The ears are pointed. A much larger bat than its relative, the Southern Yellow Bat. Forearm 46–50mm.

  SOUTHERN YELLOW BAT Lasiurus ega 109–131mm, 42–58mm, 10–14g

  Has yellow fur that extends over the basal third to half of the tail membrane, and a short rostrum. Forearm 37–43mm (red area on map).

  WESTERN YELLOW BAT Lasiurus xanthinus 102–118mm, 38–56mm, 10–15g

  (Not pictured) Recently split from the Southern Yellow Bat based on genetic data, the two are best distinguished by range (see yellow area on map of Southern Yellow Bat). The pelage of the Western Yellow Bat is slightly brighter yellow, especially on the tail membrane.

  HOARY BAT Lasiurus cinereus 99–140mm, 40–64mm, 20–35g

  Large, dark bat with grizzled fur that is frosted with white and marked with a yellow collar. The frosting gives this bat a hoary appearance. The fur extends across the tail membrane, and the ears are thickened, short, and rounded. The tragus is short and broad. Forearm 46–55mm.

  SILVER-HAIRED BAT Lasionycteris noctivagans 90–117mm, 31–50mm, 9–12g

  Beautiful dark brown or black bats with frosted hair on the back that extends down onto the basal portion of the tail membrane. The ears are short and rounded, and the tragus is blunt and curved forward. Forearm 37–47mm.

  PLATE 68

  GIANT-EARED BATS

  SPOTTED BAT Euderma maculatum 107–125mm, 47–55mm, 15–22g

  Unmistakable, with three white spots on the back, and large, pinkish ears. One of North America’s most beautiful bats. Forearm 48–54mm. It feeds on a variety of insects, particularly moths, and has some echolocation calls that sound like clicks to humans. Widespread but rarely seen, the Spotted Bat lives in the mountain and basin country of western North America from sea level to 3000m, and frequents open ponderosa pine woodlands in many areas.

  RAFINESQUE’S BIG-EARED BAT Corynorhinus rafinesquii 80–110mm, 42–54mm, 8–14g

  Small bat with large ears, toe hairs that extend beyond the tips of the claws, bicolored belly fur, and two large, fleshy lumps on each side of the snout. Forearm 38–44mm. Agile flyers, they feed on flying insects, mainly well after dark, and they return to the roost before dawn. Forms small colonies in a wide variety of roosts, including man-made structures, caves, hollow trees, and under loose tree bark. Most common in forested areas and along streams in the southeastern United States.

  TOWNSEND’S BIG-EARED BAT Corynorhinus townsendii 89–116mm, 33–54mm, 9–12g

  Has huge ears and a pair of glandular lumps on either side of the nose. The back is pale to reddish brown and the belly is pale buff. The western analogue of Rafinesque’s Big-eared Bat, it is distinguished by belly fur color. Lacks the leaflike lappets of Allen’s Big-eared Bat. Forearm 39–47mm. Uncommon and sensitive to disturbance at the roosts. Subspecies from the Ozark Mountains(C. t. ingens) and limestone caves of Kentucky, West Virginia and Virginia(C. t. virginianus) are Endangered. Forages late, which makes it difficult to observe in flight. Often hunts in edge habitats between forest and open areas.

  ALLEN’S BIG-EARED BAT Idionycteris phyllotis 103–135mm, 40–53mm, 8–16g

  Unique with big ears and small lappets that project forward from the base of each ear, extending over the snout. This small bat looks large, owing to huge ears and long, lax, yellowish-gray to blackish-brown fur. Forearm 41–49mm. In the open, they emit loud clicks at about 1-second intervals, sounds that are audible to humans. It is known from a variety of both arid and wooded habitats in southwestern North America.

  PALLID BAT Antrozous pallidus 92–135mm, 35–53mm, 13–29g

  A whitish bat with orange shoulders and large, well-separated pinkish ears. The eyes are relatively large, and the large muzzle is bare. Forearm 48–60mm. Gregarious and locally common in the west, this bat has a distinctive odor, which emanates from glands on the muzzle. Unique foraging style allows it to pick up prey, such as scorpions, from the surface of the ground. Breeding takes place in the fall, but females store sperm until ovulation occurs in the spring, resulting in births during May–June. Uses a variety of arid and semiarid habitats.

  PLATE 69

  LONGER-EARED MYOTIS

  MYOTIS BATS-This diverse group of small-bodied bats are among the most common species in North America. They are small, with upperparts generally brownish, and underparts somewhat paler. All are insectivorous, and most roost in colonies, ranging in size from a few dozen to thousands of individuals.

  SOUTHWESTERN MYOTIS Myotis auriculus 85–101mm, 34–49mm, 6–10g

  Medium-sized, with long, brownish ears. Lacks the visible fringe of hairs on the tail membrane that the Fringed Myotis has, and differs from the Long-eared Myotis in having slightly shorter ears (less than 21mm), paler flight membranes, and hair on the back that is brownish rather than blackish at the base. Forearm 38–40mm. Roosts in small groups in caves. Feeds by hovering and gleaning large insects from tree trunks and buildings. Occurs from desert grasslands up into coniferous forests in southwestern mountains.

  FRINGED MYOTIS Myotis thysanodes 80–99mm, 35–45mm, 6–12g

  Easily distinguished by long ears and distinct fringe of hairs along posterior edge of tail membrane. Has the shortest ears among this group of long-eared Myotis. Forearm 40–46mm. Females and young found in maternity colonies in caves, mines, and buildings at middle elevations from April to September. Males more likely to roost alone. Occurs in wide range of desert, grassland, and woodland habitats.

  LONG-EARED MYOTIS Myotis evotis 87–100mm, 36–41mm, 5–8g

  Differs from other long-eared Myotis in slightly larger body size, longer (more than 21mm) ears that are glossy dark brown to black, and lack of fringe on tail membrane. Forearm 36–41mm. Roosts singly or in groups of up to 30 under bark, bridges, and rocks, and in buildings, caves, crevices, hollow trees, mines, and sink holes. Forages in vegetated areas, where it gleans insects from the surface of the vegetation. Favors coniferous forest, but occurs into riparian desert scrub throughout much of western North America.

  KEEN’S MYOTIS Myotis keenii 63–93mm, 35–44mm, 4–6g

  Small long-eared bat with glossy dark brown fur on back, darker shoulder spots, and ears that extend slightly beyond nose when bent forward. The tail membrane has a few scattered hairs, but no obvious fringe. Forearm 34–39mm. Found individually or in small groups in caves or under the bark of trees. Hibernates colonially, occasionally with other species. Occupying the smallest range of any North American bat, Keen’s Myotis lives in dense pacific coastal forests of British Columbia, extending barely into southeastern Alaska and northwestern Washington.

  NORTHERN MYOTIS Myotis septentrionalis 80–96mm, 29–46mm, 4–11g

  A long-eared bat with long, sharply pointed tragus. Differs from Long-eared Myotis in having slightly paler ears, and from Keen’s Myotis in having slightly paler shoul
der spots and lacking the few scattered hairs on the tail membrane. Forearm 35–40mm. Hibernates in caves and mines. Nursery roosts are under loose tree bark, or in buildings. Prefers coniferous forests, but lives in a variety of woodlands.

  PLATE 70

  WESTERN MYOTIS 1

  CALIFORNIAN MYOTIS Myotis californicus 70–94mm, 31–42mm, 3–5g

  Tiny bat with short ears, relatively short hind feet, and an obviously keeled calcar. Differs from Long-legged Myotis in having shorter forearm and tibia, and less fur on ventral surface of wing membrane. Very similar to Western Small-footed Myotis, but Californian Myotis is slightly more delicate, often has tricolored pelage, and hair that extends further down the forehead. Forearm 30–35mm. Flies slowly but acrobatically early in the evening, often less than 3m above the ground, and frequently over or near water. Summer roosts include caves, mines, on rocky hillsides, under tree bark, on shrubs, and even on the ground. In winter it hibernates in caves and mines, however, at low elevations some animals may be active year round. Occupies deserts and arid interior mountain basins in western North America.

  WESTERN SMALL-FOOTED MYOTIS Myotis ciliolabrum 76–90mm, 32–44mm, 3–7g

  Dark wing, ears, and black mask around face contrast its paler fur. Color is flaxen above, and nearly white below. Similar to Californian Myotis in having small feet (<9mm) and a keeled calcar, but differs from that species in appearing slightly more robust, having bicolored pelage with a slight, glossy sheen, a slightly longer rostrum, and less hair on the forehead. Forearm 30–34mm. Breeds in fall, fertilization occurs in spring, young are born May–July and begin to fly about a month later. Often roost colonially. Hibernates in caves or mines, alone or in small groups, and unlikely to be active during winter. Reported to chew their food to a very high degree. Uses high plains east of the continental divide where it occupies rocky outcrops in short grass habitats (yellow area on map).

  DARK-NOSED SMALL-FOOTED MYOTIS Myotis melanorhinus 76–98mm, 30–45mm, 4–5g

  Like the Western Small-footed Myotis but with darker fur on the forehead and back. Recently recognized as a distinct species. Color is a rich yellow, with buff underparts and black ears, nose, and wings. Feet are short and calcar is obviously keeled. Very tip of tail extends 1.5–2.5mm beyond the tail membrane in some animals. Forearm 30–34mm. An agile but erratic flier, it hunts insects by flying irregular circuits from 1m above the ground to the tree-tops. Roosts in buildings, bridges, mines or natural caves. Spends the winter in caves or mines where it roosts alone or with up to 5 others. Occurs west of the continental divide, where it occupies rocky areas in coniferous forests from 300 to 3300m (red area on map of Western Small-Footed Myotis).

  LONG-LEGGED MYOTIS Myotis volans 76–106mm, 29–49mm, 5–10g

  Large-sized Myotis with longer, denser fur on the underside of the wing between the knee and elbow than in other species of Myotis. Has short, keeled calcar, and short, rounded ears. Color varies from dark brown to reddish buff, with darker ears and membranes. Forearm 35–42mm. Strong flyers, they have been clocked at 15–17kph. Some individuals may return to the same foraging area night after night. Maximum life span is at least 21 years based on capture-recapture records. Roosts in ponderosa pine snags, crevices, cracks, caves, and abandoned buildings, and in winter they hibernate in caves and mine tunnels. Occupies rugged, mountainous terrain, most commonly 2000–3000m. Primarily limited to coniferous forests, but also found in oak and riparian woodlands, extending down into desert areas almost to sea level.

  PLATE 71

  WESTERN MYOTIS 2

  CAVE MYOTIS Myotis velifer 83–102mm, 39–47mm, 9–14g

  One of the largest species of Myotis in North America, with fur varying from light brown to almost black. Has a stubby-nosed appearance, with the ears barely reaching to the end of the nose when bent forward. Forearm 40–45mm. In some caves containing large numbers of these bats the humidity is very high and the ammonia content of the air from the bats’ urine can cause the pelage to bleach to a paler color. Flies stronger and less erratically when foraging than most other species of Myotis. Feeds on moths and beetles, and is most active just after dusk and just before dawn. Forms large colonies in caves in lowlands of southwestern North America. Some of these are year-round residents hibernating in the caves during the winter. Other individuals migrate south for the winter, and some may actually seek colder caves at higher elevations for more efficient hibernation.

  LITTLE BROWN MYOTIS Myotis lucifugus 60–102mm, 25–55mm, 7–13g

  An otherwise undistinguished species of Myotis that differs from the Yuma Myotis in having glossy fur, from the Indiana Myotis in lacking a keel on the calcar and having longer toe hairs, from the Long-legged Myotis in having less fur on the underside of the wing, and from Southwestern, Long-eared, Keen’s, and Northern Long-eared Myotis in having shorter ears (less than 16mm). Skull shows a more gradually ascending forehead than in the Yuma Myotis. Forearm 33–41mm. Nocturnal and adept at using echolocation to catch their insect prey in mid-air. They may migrate up to 1000km between summer breeding areas and winter hibernacula. Widespread and common in buildings in summer, and hibernates in sizeable colonies in caves and mines.

  ARIZONA MYOTIS Myotis occultus 83–95mm, 34–45mm, 5–10g

  Almost identical to Little Brown Myotis, from which it was previously considered a subspecies, but lives in the southwestern United States and Mexico. Fur is slightly paler and redder in the Arizona Myotis, and the skull almost always has a sagittal crest, which is usually lacking in the Little Brown Myotis. Premolars are reduced, but has otherwise large teeth. Forages over water, skimming low over large open bodies of water to drink or picking up insects. Forms large maternity colonies in buildings or caves. Inhabits most isolated mountain ranges from Arizona to Texas, and occupies a wide range of habitats from upper Sonoran to boreal forests.

  YUMA MYOTIS Myotis yumanensis 75–89mm, 29–43mm, 4–7g

  Medium-sized Myotis with short ears (extend less than 2mm beyond nose when bent forward), and an unkeeled calcar. Very similar to the Little Brown Myotis, but the Yuma Myotis is slightly smaller, with less glossy fur, and paler ears. Skull shows a more abruptly ascending forehead than the Little Brown Myotis. Forearm 30–38mm. Active at dusk, they are frequently seen foraging low over or near open water in valleys of western mountains. They are less active in the middle of the night, although sometimes they forage again just before dawn, primarily feeding on moths and flies. Commonly found in desert areas, but never far from water sources. They lack special adaptations to desert habitats and quickly dehydrate if kept from water. Summer roosts are found in buildings, under bridges, in crevices of cliffs, and in caves and mines throughout the southwest.

  PLATE 72

  EASTERN MYOTIS

  LITTLE BROWN MYOTIS Myotis lucifugus

  Differs from Indiana Myotis in lacking a keel on the calcar and having more and longer toe hairs. (See page 158 for more details.)

  GRAY MYOTIS Myotis grisescens 80–96mm, 32–45mm, 4–6g

  A large Myotis with uniformly-colored gray or brown hairs on the back. Unique in having the wing membranes attached to the ankles rather than to the toes, and the calcar lacks a keel. Forearm 40–46mm. Hind feet are less haired than in the Little Brown Myotis. Females form large maternity colonies in caves in the summer. Endangered, virtually the entire population hibernates in nine caves in the southeastern United States. The Gray Myotis forages mainly over water and ranges over long distances from summer day roosts. Found primarily in karst areas with underlying limestone caves in the southeast and south-central U.S.

  EASTERN SMALL-FOOTED MYOTIS Myotis leibii 73–82mm, 29–36mm, 3–7g

  The smallest North American Myotis differs from other eastern Myotis in its smaller size, shorter ears and hind feet, and keeled calcar. Face and ears also darker black than other overlapping bats. Many roosting bats have orange chiggers on their ears. Small feet have no hair on the toes. Similar to Western Small-footed and Californian Myotis,
but range does not overlap with those species. Individual hairs are varying shades of brown, but overlain with a somewhat golden sheen. Forearm 30–35mm. Uncommon and limited to eastern deciduous and coniferous forests.

  SOUTHEASTERN MYOTIS Myotis austroriparius 77–89mm, 26–44mm, 5–7g; 80–97mm, 29–42mm, 5–8g

  Small bat with somewhat dull, wooly pelage. Usually dull gray to gray-brown, but some individuals are a bright orange-brown. Fur on underside is dark brown to black at the base, with contrasting white at tip. No prominent keel on calcar. Toes have long hairs extending beyond tips of claws. Differs from Northern Myotis by having smaller ears, and from Little Brown Myotis in lacking the glossy pelage of that species. Forearm 33–42mm. Prefers caves near water, or even those that contain water. Can be seen foraging near the surface of the water on summer evenings. Occurs in both coniferous and deciduous forests of the southeastern U.S.

  INDIANA MYOTIS Myotis sodalis 73–99mm, 29–43mm, 3–10g