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House Bat Management

Appendix B

Species Accounts

Myotis lucifugus. Little brown bat, common bat, cave bat, little brown myotis.

Wingspread: 222 to 269 mm (8.9 to 10.8 in.).

Forearm: 34 to 41 mm (1.3 to 1.6 in.).

Recognition: Fur is dense, fine, and glossy. Both sexes a rich brown, almost bronze; juveniles may be almost black. Ears and membranes are a glossy dark brown. There are many small brown species but this is the one most often found in buildings (Fig. 24).

Distribution: From Labrador to southern Alaska, the mountains of southern California, as well as from the Appalachians to Georgia and west into Arkansas. Stragglers can be found in New Mexico, Texas, Mississippi, and Alabama, and the coastal parts of the Carolinas.

Comments: One of the most abundant of all colonial bats in the northern part of its range; is common within its range. In the spring and summer females form maternity colonies of hundreds of individuals or more in attics, barns, and other retreats that are dark and hot during the daytime. In winter, these bats hibernate in caves and mines, frequently returning year after year to the same nursery colony and hibernation cave. Colonies are far more common near lakes and rivers. Rabies is seldom a problem with this species since it is not an effective biter due to its small teeth.

  JPG -- A Little brown bat.
Fig. 24.  Little brown bat, Myotis lucifugus. (Photo from Barbour and Davis 1969)

Eptesicus fuscus. Big brown bat, house bat, barn bat, dusky bat.

Wingspread: 325 to 350 mm (13 to 14 in.).

Forearm: 42 to 51 mm (1.7 to 2.0 in.).

Recognition: Probably the largest bat commonly found in buildings except for the pallid bat. Most adults are copper-colored, but color may vary from light to dark brown. Each hair is bicolored--the basal half being almost black and the outer half brown. Face, ears, and membranes are dark brown to nearly black. Sexes are colored alike and show no seasonal variation (Fig. 25).

Distribution: From Alaska and southern Canada south through New England to Florida, extending coast to coast. It is abundant throughout most of its range, except in the far northern States and the deep South. Apparently unknown from southern Florida and much of central Texas.

Comments: The big brown bat is probably the colonial bat most familiar to man. In summer, it commonly roosts in attics, belfries, and barns; behind awnings, doors, and shutters; but seldom in caves. It is a hardy species that can endure subfreezing temperatures but is not as tolerant of high temperatures as is the little brown bat. During hot weather, it may crawl into rooms from crevices of fireplaces, or both young and adults may appear in basements if the space between the inside and outside walls is continuous from attic to basement. Colonies vary in size between 12 and 200. They have a remarkable homing instinct and do not migrate far from their place of birth. They are one of the last bats to hibernate in fall and first to arouse in spring, and may be seen flying about at dusk in late November and early March, spending the winter in buildings, caves, mines, and similar shelters. Eptesicus is easily recognizable due to its large size and steady, straight flight at a height of 6.1 to 9.1 m (20 to 30 ft) or more. After feeding, the bat flies to a night roost to rest, favoring porches, brick houses, garages with open doors, or a breezeway. The tell-tale signs of its presence are a few droppings left each morning below the roost. Big brown bats can inflict a painful bite if carelessly handled. This is one of the species most often rabid.

  JPG -- A Big brown bat.
Fig. 25.  Big brown bat, Eptesicus fuscus. (Photo from Barbour and Davis 1969).

Tadarida brasiliensis. Mexican free-tailed bat, free-tailed bat, guano bat.

Wingspread: 290 to 325 mm (11.3 to 13 in.).

Forearm: 36 to 46 mm (1.4 to 1.8 in.).

Recognition: A rather small bat with long narrow wings, and about one-half of the tail extending beyond the interfemoral membrane. The ears almost meet at the midline but are not joined and have a series of papillae or wartlike structures on the anterior rims. The upper lips are wrinkled. It is the smallest of the free-tailed bats in the United States. The body and membranes are dark brown. Individuals are dark gray or pale brown due to bleaching by ammonia fumes from guano deposits (Fig. 26).

Distribution: Found from California to Florida, migrating into Texas and Mexico. Occasionally found as far north as Oregon, Nevada, Utah, and in the East as far north as North Carolina.

Comments: This species is the most colonial of all bats. The habitat of the free-tailed bat differs in various parts of the United States. It inhabits buildings on the West Coast and in the Southeast. It is primarily a cave bat in Arizona, New Mexico, Oklahoma, and Texas. Maternity colonies of 1,000 or more may inhabit a single-building in California. In Florida, the species never enters caves and thousands have been found in a single building. Jennings (1958), cited by Barbour and Davis (1969), wrote that in Florida nearly every town harbors one or more colonies of free-tailed bats, yet the Department of Health and Rehabilitative Services stated, "We receive few complaints of bats in buildings . . ." (F. L. Hoff, personal communication). In Texas, Davis (1962), cited by Greenhall and Paradiso (1968), stated that "throughout south Texas every group of a dozen or more buildings is likely to have at least one guano bat roost for some period during the year." An estimate was given of 3 roosts per 1,000 human population, each having over 100 bats. Texas has a house bat problem according to officials. In Texas it is also a cave bat and Davis et al. (1962) estimated that the total population in caves in 1957 was at least 100 million. At Carlsbad Caverns, New Mexico, the population has been estimated from as high as almost 9 million in June 1936 (Allen 1962) to a low of 0.25 million (Edgerton 1966; Petit 1978) due to pesticide poisoning. Tadarida brasiliensis has been found positive for rabies. No one should enter a cave containing thousands of bats unless immunized against rabies. It is thought that two human fatalities from rabies in a Texas cave resulted from airborne exposure attributed to this species.

  JPG -- A Mexican free-tailed bat.
Fig. 26.  Mexican free-tailed bat, Tadarida brasiliensis. (Photo from Barbour and Davis 1969).

Myotis yumanensis. Yuma myotis.

Wingspread: About 235 mm (8.7 in.).

Forearm: 32 to 38 mm (1.3 to 1.5 in.).

Recognition: Light tan to dark brown, the underparts whitish to buffy. The membranes are darker than the body (Fig. 27).

Distribution: Found in western North America from Canada to Mexico.

Comments: More closely associated with water than any other bat except the gray bat (Myotis grisescens). In North America, it is always found near open water. A nuisance in California where large nursery colonies may be found in buildings, attics, porches, and abandoned cabins. A colony of about 5,000 inhabited a church belfry in Nevada and some transients were found in the ventilators of a building in Berkeley, California (Barbour and Davis (1969). It has been found rabid but rarely is a hazard to humans.

  JPG -- Yuma myotis.
Fig. 27.  Yuma myotis, Myotis yumanensis. (Photo from Barbour and Davis 1969).

Antrozous pallidus. Pallid bat, desert pallid bat.

Wingspread: 360 to 390 mm (13 to 14 in.).

Forearm: 48 to 60 mm (1.9 to 2.4 in.).

Recognition: Light yellow above the hairs tipped with brown or gray, whereas the underparts are pale creamy, almost white, but not bicolored. Membranes are tan. This is a large bat with big ears, large eyes, and broad wings. The pig-like snout is distinctive (Fig. 28).

Distribution: Found primarily in the western United States from the Pacific Northwest to the Southwest.

Comments: This colonial species is occasionally troublesome in California where the same open shelter (readily accessible by flight) serves as both day and night roost. The bats hang from the rafters and their droppings foul hay in barns and cars in garages. This species has one of the most unique feeding habits of any North American bat. Prey is mainly from the ground and little, if any, food is captured in flight. Food consists of scorpions, grasshoppers, Jerusalem crickets, June beetles, and other ground beetles. It is a relatively slow flier, foraging close 0.9 to 1.2 m (3 to 4 ft) to the ground. It has been found rabid but is rarely a problem to humans.

  JPG -- A Pallid bat.
Fig. 28.  Pallid bat, Antrozous pallidus. (Photo from Barbour and Davis 1969).

Lasionycteris noctivagans. Silver-haired bat, silvery black bat, black bat.

Wingspread: 270 to 310 mm (10.5 to 12.1 in.).

Forearm: 37 to 44 mm (1.5 to 1.8 in.).

Recognition: The fur is long and soft. The hairs are strongly tipped with silvery white which produces a frosted appearance on both sexes. The back and sides are blackish brown. The membranes are blackish. The tail or interfemoral membrane is lightly furred only on the basal half close to the body on the upper surface (Fig. 29).

Distribution: All over northern North America.

Comments: This medium-sized bat is smaller than the big brown bat and larger than any of the myotis. It is one of the species most often involved in causing rabies in humans. Exposure is almost entirely the result of careless handling of individual sick bats that are found on the ground or on the sides of buildings.

  JPG -- A Silver-haired bat.
Fig. 29.  Silver-haired bat, Lasionycteris noctivagans. Note hairs of back tipped with white. (Photo from Barbour and Davis 1969).

Lasiurus borealis. Red bat, leaf bat, tree bat, northern bat, New York bat.

Wingspread: 290 to 332 mm (11.6 to 13.3 in.).

Forearm: 35 to 45 mm (1.4 to 1.8 in.).

Recognition: This solitary medium-sized bat is easily distinguished by its bright rusty color, short rounded ears, and long pointed wings. The interfemoral membrane is thickly furred on the entire upper surface. The underparts are paler than the back, and hairs lack much of the white tipping. There is usually a white shoulder spot. Males tend to be redder and less frosted than the females (Fig. 30).

Distribution: All over North America.

Comments: This solitary bat extends its long tail membrane straight out in flight. It only occasionally enters buildings during migration and seems to have well-developed flyways which it follows annually. Unlike other bats, copulation begins while the bats are in flight and sometimes ends on the ground where they may be encountered. Red bats produce larger litters (up to five individuals) than other species of bats. They are rarely encountered by humans except when sick, which explains the high incidence of rabies in those sampled.

  JPG -- A Red bat.
Fig. 30.  Red bat, Lasiurus borealis hanging by both legs. The heavily furred interfemoral membrane is extended. Note short rounded ears. (Photo from Barbour and Davis 1969).

Lasiurus cinereus. Hoary bat, frosted bat, great northern bat, twilight bat.

Wingspread: 380 to 410 mm, (15.2 to 16.4 in.).

Forearm: 46 to 58 mm (1.8 to 2.3 in.).

Recognition: This solitary bat is one of the largest in North America, larger than the big brown bat. It is dark-colored and heavily furred. The tips of many hairs are white, giving an overall frosted, hoary appearance. The ears are relatively short and edged with black. Usually there is a white shoulder spot. The membranes are brownish. The upper surface of the interfemoral or tail membrane is completely furred. The much smaller silver-haired bat (which lacks fur on the feet, ears, and underside of the wings) is the only other bat that could be confused with the hoary bat. The upper basal surface of the tail membrane is lightly furred (Fig. 31).

Distribution: Lasiurus cinereus is the most widely distributed of all U. S. bats, probably occurring in all 50 States—although not yet reported from Alaska. A smaller, more reddish race, the Hawaiian hoary bat (L. semotus), is restricted to the Hawaiian Islands and is on the Endangered Species List.

Comments: It is exceeded in size only by the largest free-tailed bats. Rabid individuals are occasionally found except on the Hawaiian Islands. Its habits seldom bring it into direct contact with man, but because of its exceptionally large teeth it is an effective biter and potential transmitter of rabies if carelessly handled.

  JPG -- A Hoary bat.
Fig. 31.  Hoary bat, Lasiurus cinereus. Defensive pose. Note silver-tipped hair and black-edged ears. (Photos from Barbour and Davis 1969).

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