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Funnel-Eared Bats: Natalidae

FUNNEL-EARED BATS: Natalidae


FUNNEL-EARED BAT (Natalus stramineus): SPECIES ACCOUNT

PHYSICAL CHARACTERISTICS

Funnel-eared bats get their name from the shape of their ears, which are large and formed like a funnel. They are small and slim with relatively long legs that can be longer than the head and body combined. Combined the head and body is approximately 2 inches (5 centimeters) long. Their wings are long and slender with a slender tail that is completely enclosed in a tail membrane. They also have small eyes.

Adult males have a large structure typically in the center of the forehead called the natalid (NAT-ah-lid) organ. The function of this is uncertain.

The fur of these bats is soft and long with color ranging from gray, yellowish, reddish, to deep chestnut. One species, the Mexican funnel-eared bat, has two color phases, or types: one in which fur is light, tan to pinkish light brown, and the other in which fur is darker, a yellowish or reddish brown. The belly is paler in both phases.

GEOGRAPHIC RANGE

The five species of funnel-eared bats are found in several areas. One species is found in northern Mexico, eastern Brazil, and specific Caribbean islands. Another species occurs in northern South America and nearby islands. The other three species are found on islands in the Caribbean.

HABITAT

These bats live in lowland forests that are dry and deciduous, forests where the trees lose their leaves at the end of the growing season. In general, they are found below 984 feet (300 meters). In Venezuela, these bats were found in habitats from sea level to about 8,200 feet (2,500 meters). Typically, these bats roost, rest or settle, in the darkest areas of caves and mine tunnels. They also have been found roosting in tree hollows.

DIET

These bats feed on small insects.

BEHAVIOR AND REPRODUCTION

Funnel-eared bats form colonies, groups, of up to 300 individuals. Some observations have also found fewer than a dozen individuals. These bats often roost with other families of bats. Northern populations may travel to warmer areas in the winter. Some species of bats have been observed hanging singly, alone.

Since they are nocturnal, active at night, funnel-eared bats leave their roost about half an hour after sunset to forage, search, for food. They use echolocation (eck-oh-loh-KAY-shun) to locate their prey, animals hunted for food. Echolocation is the detection of objects by emitting, sending out, sounds and listening to the returning sounds that bounce off objects. These bats flutter their wings rapidly while flying, like a moth, and can maneuver (mah-NOO-ver) easily. This allows them to enter and exit dense plant growth.

Females bear a single offspring late in the dry season, when they establish separate maternity colonies. Little is known about the mating behavior of these bats, but findings show that males mate with more than one female during the season.

FUNNEL-EARED BATS AND PEOPLE

Bacteria that cause fevers in humans have been isolated in one species of funnel-eared bat, the Trinidadian funnel-eared bat. Many bats, such as this one, have bacteria or other organisms associated with their droppings, waste, that can lead to diseases in people.

WHAT A BABYFACE

The genus (JEE-nus) name Natalus comes from the Latin word natus meaning to be born. (Natus is also the root word for nature.) These bats were given this name because they are small and look like newborns even as adults.

CONSERVATION STATUS

The World Conservation Union (IUCN) lists Gervais's funnel-eared bat as Near Threatened (not currently threatened, but could become so in the future), and the Bahaman funnel-eared bat as Vulnerable, facing a high risk of extinction in the wild.

FUNNEL-EARED BAT (Natalus stramineus): SPECIES ACCOUNT

Physical characteristics: Funnel-eared bats, also called Mexican funnel-eared bats, have the funnel-shaped ears that are characteristic of the family. They have long, slender hind legs. They have black, stiff hairs above the upper lip, appearing like a moustache, and white hairs below the lower lip. The natalid organ is shaped like a bell and covers the muzzle, the snout.

Fur color occurs in both a light and a dark phase. The light phase is generally a light to medium tan and the dark phase is a reddish brown. The belly is paler in both phases, and of a similar color.

Geographic range: Funnel-eared bats are found in northern Mexico to eastern Brazil, Cuba, Jamaica, Lesser Antilles, and Tres Marias islands off western Mexico.


Habitat: Funnel-eared bats generally live in deciduous forests. They may also live in moister forest areas.


Diet: Funnel-eared bats feed on insects.


Behavior and reproduction: These bats were found roosting in large colonies with thousands of individuals in Venezuela. At high altitudes, some colonies may go into torpor, a dormant state, during the cooler months.

In general, bats of this species roost in the darkest areas of caves and mines. Females form maternity roosts during the breeding season. Gestation, pregnancy, lasts approximately ten months. Offspring are born weighing more than 50 percent of the mother's weight.


Funnel-eared bats and people: There is no known special significance between funnel-eared bats and people.


Conservation status: Funnel-eared bats are not considered threatened by the IUCN. ∎

FOR MORE INFORMATION

Books:

Fenton, M. Brock. Bats. New York: Checkmark Press, 2001.

Fenton, M. Brock. The Bat: Wings in the Night Sky. Buffalo, NY: Firefly Books, 1998.

Nowak, Ronald M. "Funnel-eared Bats." Walker's Mammals of the World 5.1 Online. Baltimore: Johns Hopkins University Press, 1997. http://www.press.jhu.edu/books/walkers_mammals_of_the_world/chiroptera/chiroptera.natalidae.natalus.html (accessed on July 5, 2004).

Richardson, Phil. Bats. London: Whittet Books, 1985.

Ruff, Sue, and Don E. Wilson. Bats. New York: Benchmark Books, 2001.

Schober, Wilfried, and Eckard Grimmberger. The Bats of Europe and North America. Neptune City, NJ: T.F.H. Publications, Inc., 1997.

Web sites:

"Discover the Secret World of Bats." Bat Conservation International, Inc. http://www.batcon.org (accessed on July 5, 2004).

Simmons, Nancy. "Natalus stramineus, Mexican Funnel-eared Bat." Digi-Morph. http://www.digimorph.org/specimens/Natalus_stramineus/head/ (accessed on July 5, 2004).

Weinstein, B. and P. Myers. "Family Natalidae: Funnel eared bats." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Natalidae.html (accessed on July 5, 2004).

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