Discover Life | All Living Things | IDnature guides | Mammalia | Vespertilionidae | Eptesicus fuscus

Species Description

• Adult total length: 3 3/4 - 5 1/8 in. (94 - 130 mm)

• Tail: 1 3/8 - 2 1/8 in. (35 - 52 mm)

• Hind foot: 3/8 - 1/2 in. (10 - 11.5 mm)

• Weight: 6/10 - 7/10 oz. (14 - 21 g)

• Physical Characteristics: Bats are unique among mammals because their forelimbs are specialized for true flight. Flight membranes, which are actually extensions of the skin of the back and belly, connect the body with the wings, legs, and tail. Unlike birds, bats use both legs and wings during flight. Other modifications for flight include greatly elongated fingers to provide support for the wing membrane, a keeled sternum for the attachment of the enlarged flight muscles, and fusion of some vertebrae. The membrane extending from the tail to the hind legs is known as the interfemoral membrane. The big brown bat is one of the largest bats in the park. It has a wingspan of approximately 12 inches (305 mm). Along with its size, it can be distinquished from all bats in the park by its long, uniformly dark brown fur. The fur of the undersurface is paler. The blackish ears are short, broad, and rounded and barely reach the nostrils when laid forward. The top of the blackish interfemoral membrane is naked except for a sprinkling of hairs on the basal fourth.

left lateral view of skull and mandible	dorsal view of skull	ventral view of skull

Index

Photographs

Eptesicus fuscus

Index

Phylogeny

All of the park's caves provide critically important habitats for bats. During the summer, these bats are usually found in attics, barns, and bridges. During the coldest weather, these bats move into caves and mines. Big brown bats usually hang alone while hibernating, although small clusters of fewer than 20 bats also occur (Kurta, 1999). The big brown bat mainly hibernates in buildings with only a few individuals overwintering in caves.

Index

Natural History

• Reproduction
  Maternity colonies of the big brown bat containing up to several hundred individuals form during the summer (Harvey et al., 1999). Females store sperm in their reproductive tracts during the winter and ovulate in early spring, at the time of arousal from hibernation. Following a gestation period of 60 days, breech birth occurs. Eighty percent or more of females in eastern North America produce twin pups, but litter size in the West is generally one. Young are born weighing an average of 3.3 g and learn to fly at 18-35 days of age.

• Longevity
  There are numerous records of these bats living 10 years or more. The oldest recorded age for any big brown bat was at least 19 years (Paradiso and Greenhall, 1967; Kunz, 1982).

• Terrestrial Ecology
  The senses of sight and hearing are well developed in bats. Since most bats become active near dusk and are active much of the night, sight is of little importance in navigation and in the capture of prey. Instead, they use echolocation, a system somewhat similar to radar. They emit ultrasonic calls far above the range of human hearing that are reflected from objects ahead of them. They hear the echoes and are able to avoid obstacles and find food in total darkness. Different species can be distinguished by differences in the structure of their echolocation calls (Fenton and Bell, 1981).

  The large size and steady flight serve as good field identification characteristics. During feeding maneuvers, the tail and wing membranes are used to capture and restrain prey. Some insects are captured by the tail membrane, which forms a pouch-like compartment. The bat must bend its head forward in order to grasp the insect with its teeth and take it into its mouth. Sometimes the bat may use its mouth to capture an insect from its wing.

  Eleven species of bats have been recorded in the park and all feed exclusively on insects. During the colder months when flying insects are unavailable, bats must either hibernate or migrate to warmer areas. Eight of our bats are known to hibernate. Only three - the red bat, hoary bat, and the silver-haired bat - are migratory. Bats have been seen flying over the park during every month of the year. When flying during the winter, however, they do not feed.

• Predators and Defense
  No predators recorded from the park.

• Parasites
  None recorded from the park.

• Transmittable Diseases
  Bats are capable of transmitting two diseases to humans - rabies and histoplasmosis. Histoplasmosis is a disease caused by inhaling dust that contains contaminated spores. Tuttle (1988) stated: "Less than a half of 1 percent of bats contract rabies, a frequency no higher than that seen in many other animals. Like others, they die quickly, but unlike even dogs and cats, rabid bats seldom become aggressive." Bats do not attack when they get rabies; they just lie in one place. Although it is rare for humans to contract rabies from infected bats, persons handling them should be aware of this possibility.

• University of Michigan, Museum of Zoology
• eNature

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Acknowledgements

• Text
  • Dr. Donald W. Linzey, Wytheville Community College - wclinzd@wcc.vccs.edu
  • Christy Brecht, Wytheville Community College - wcbrecc@wcc.vccs.edu

• Photographs
  • Roger Barbour

• Map development
  • Richard Schulz, Great Smoky Mountains National Park - richard_schulz@nps.gov

• Web page design & coding
  • Denise Lim, University of Georgia, Athens
  • John Pickering, University of Georgia, Athens

• Barbour, R.W. and W. H. Davis. 1969. Bats of America. Lexington: The University Press of Kentucky.

• Fenton, M.B., and G.P. Bell. 1981. Recognition of insectivorous bats by their echolocation calls. Journal of Mammalogy 62 (2): 233-243.

• Harvey, M.J., J.S. Altenbach, and T.L. Best. 1999. Bats of the United States. Little Rock: Arkansas game and Fish Commission.

• Kunz, T. H. (ed). 1982. Ecology of Bats. New York: Plenum Press.

• Kurta, A. 1999. Big brown bat. Pages 115-116. In: D. E. Wilson, and S. Ruff (editors.). The Smithsonian Book of North American Mammals. Washington, D.C.: Smithsonian Institution Press.

• Kurta, T. H. and R. H. Baker. 1990. Eptesicus fuscus. Mammalian Species No. 356: 1-10. American Society of Mammalogists.

• Linzey, D. W. 1995a. Mammals of Great Smoky Mountains National Park. The McDonald & Woodward Publishing Company, Inc., Blacksburg, Virginia.

• Linzey, D. W. 1995b. Mammals of Great Smoky Mountains National Park-1995 Update. Journal of the Elisha Mitchell Scientific Society 111(1):1-81.

• Linzey, D. W. 1998. The Mammals of Virginia. Blacksburg, Virginia: The McDonald & Woodward Publishing Company, Inc

• Paradiso, J. L., and A. M. Greenhall. 1967. Longevity records for American bats. American Midland Naturalist 78 (1): 251-252.

• Tuttle, M.D. 1988. America's Neighborhood Bats. Austin: University of Texas Press.