Discover Life | All Living Things | IDnature guides | Mammalia | Vespertilionidae | Nycticeius humeralis

Species Description

• Adult total length: 3 1/8 - 3 3/4 in. (78 - 93 mm)

• Tail: 1 3/8 - 1 1/2 in. (35 - 37 mm)

• Hind foot: 1/4 - 3/8 in. (7 - 10 mm)

• Weight: 1/4 oz. (5 - 9 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. Evening bats are similar to big brown bats, but smaller. They can be distinguished by their reddish to dark brown fur above and tawny color below. The ears are blunt and rounded and both the ears and membranes are black and generally naked, although in some individuals hairs may be present on the extreme proximal portion of the inter femoral membrane.

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

Index

Natural History

• Reproduction
  Mating probably occurs in late summer and early fall, with the sperm being stored in the uterus of the female during the winter. Ovulation and fertilization occur in the spring. Females give birth to 1 to 3 pups (usually twins) during June.

• Longevity
  The average life span in the wild is probably about two years, although there are records of some individuals surviving for over five years (Watkins, 1972).

• 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).

  Evening bats leave their roost near dusk. Individuals begin flying at a height of 12 to 23 m, but as darkness falls they come much lower to the ground. They have a slow and steady flight. 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.

• eNature

Index

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. 1999a. Evening bat. Pages 117-118. In: D. E. Wilson, and S. Ruff (eds.). The Smithsonian Book of North American Mammals. Washington, D.C.: Smithsonian Institution Press.

• 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.

• 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.

• Watkins, L. C. 1972. Nycticeius humeralis. Mammalian Species No. 23: 1 - 4. American Society of Mammalogists.

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