Chiroptera Bats

Order Chiroptera (Greek for "hand wing") contains the only mammals that have evolved true flight (colugos and flying squirrels are gliders, not flyers). Living bats compose the second largest mammalian order (constituting about a fourth of all living mammals), and they play important ecological roles in insect control, pollination, seed dispersal, and fertilizer production.

Bats literally fly with their hands. Except for the thumb, the bones of the upper arm, forearm, and the four fingers are slender, elon gate, and covered by thin flight membranes extending from the sides of the body and legs; another membrane connects the legs with the tail. The earliest well-preserved bat is Icaronyc-teris index from the Late Paleocene-Early Eocene, though the evolutionary origin of bats may date back to the Late Cretaceous.

The more than 1,000 bat species are arranged into suborder Megachiroptera, containing one family (Pteropidae, Old World fruit bats or flying foxes), and suborder Microchiroptera, with seventeen families. Bats are cosmopolitan in both hemispheres, except for polar regions and remote oceanic islands. The highest diversity of bat species occurs in the neotropics, where some localities have more species of bats than all other mammal species combined. Flying foxes are the largest bats, with wingspans of up to 2 m and body

Leaf-nosed bat flying at night. Bats are nocturnal mammals that use echolocation to navigate and to track prey. (Joe McDonald/Corbis)

lengths up to 430 mm (Pteropus vampyrus). Hog-nosed bats of Thailand (Craseonycteris thonglongyai), weighing about 2 gm, with a body length of up to 30 mm (about the size of a bumblebee), are the smallest bats and possibly the smallest living mammal.

Bats are nocturnal. Most megachiropteran species use vision for orientation and seeking food. Microchiropterans echolocate for orientation and capturing prey. They produce sound from the larynx, emitting pulses (usually ultrasonic) through an open mouth, or through the nostrils in species having elaborate nose-leaves. Echolocation, which allows bats to perceive and navigate their nocturnal environment, is essential in capturing prey and avoiding obstacles. The abilities of bats to fly and echolocate are prominent factors in the successful evolutionary radiation of bats into most of the ecological niches that are occupied by diurnal birds. This diversity of species and ecologies is reflected in their food habits. Most species are insectivorous, preying upon a wide variety of insects they catch in the air, on the ground, or on the tops of leaves. Some are carnivorous, eating other bats, small rodents, frogs, and lizards. A very few species catch and eat small fish. Three neotropical species feed on the blood of other mammals and birds. Many tropical species feed exclusively on fruits and flowers or nectar and pollen.

Historically, humans have looked upon bats with fear and revulsion. Laboratory and field studies have revealed much about the fascinating biology and behavior of bats. Many people now recognize that bats are not a menace to humans, and that they play integral roles in various ecosystems. Despite the shift in many peoples' attitudes toward bats, they are still persecuted in some regions: roosts are destroyed, forest habitats are logged, and the larger-bodied flying foxes are overhunted for food.

—Mary Ellen Holden

See also: Adaptation; Adaptive Radiation; Arthropods, Terrestrial; Biogeography; Convergence and Parallelism; Evolutionary Biodiversity; Extinction, Direct Causes of; Food Webs and Food Pyramids; Mammalia; Speciation; Tropical Rain Forests

Bibliography

Hill, John E., and James D. Smith. 1984. Bats: A Natural History. Austin: University of Texas Press; Koop-man, Karl F. 1993. "Order Chiroptera." In Mammal Species of the World. 2d ed, edited by Don E. Wilson and DeeAnn M. Reeder, pp. 137-241. Washington, DC: Smithsonian Institution Press; Kunz, Thomas H., and Paul A. Racey, eds. 1998. Bat Biology and Conservation. Washington, DC: Smithsonian Institution Press; Nowak, Ronald M. 1999. Walker's Mammals of the World, 6th ed. Vol. 1. Baltimore: Johns Hopkins University Press; Wilson, Don E. 1997. Bats in Question: The Smithsonian Answer Book. Washington, DC: Smithsonian Institution Press.

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