SMOKY BATS: Furipteridae

PHYSICAL CHARACTERISTICS

Smoky bats are also commonly called thumbless bats. While they do have a thumb, it is small, enclosed in the edge of the wing, and can appear invisible. Other bats, on the other hand, use their thumbs to grip surfaces while crawling, and to hang right side up while giving birth. Smoky bats are among the smallest of bats, having a head and body length combined of 1.4 to 2.6 inches (3.5 to 5.8 centimeters). Their forearms are about 1.2 to 1.6 inches (3 to 4 centimeters) long. Females are slightly larger than males.

These bats appear delicate, with broad wings that are relatively long. The snout is pig-like in appearance, being short and turned up at the tip. Set close together, the nostrils are oval or triangular. Ears resemble funnel-eared bats. They are separate, large, and funnel-shaped, reaching almost to the jaw line. These bats have tiny eyes that are hidden by fur and their large ears. They also have long legs and short feet, with claws on the end of their feet. The tail is relatively long, but it does not reach past the edge of the tail membrane (layer of thin skin).

The fur is generally coarse. The smoky bat has triangular, wart-like fleshy projections around its mouth and lips.

GEOGRAPHIC RANGE

The two species of the family are found in different areas. The thumbless bat is found west of the Andes, from central coastal Ecuador south to northern Chile. The smoky bat is found in Costa Rica, lowland Brazil, Peru and Trinidad.

HABITAT

Furipterids (members of the family Furipteridae) live in diverse habitats. The thumbless bat has been found living in lowland rainforests to the arid (extremely dry) deserts of South America to cultivated land. The smoky bat appears to have a narrower range of habitats, found primarily in lowland, moist forests. Many of these bats live in isolated populations. They are found primarily in caves, tree hollows, and human-made structures.

DIET

Bats in this family feed on insects, primarily moths and butterflies.

BEHAVIOR AND REPRODUCTION

Little is known about the species of bats in this family. Because they are small, agile flyers in isolated populations, smoky bats are difficult to catch and study. It is known that these bats roost in colonies (groups) between 100 and 300 individuals.

Like all bats, the smoky bats become active at night (nocturnal). The long and broad shape of their wings allows them to fly slowly and with great agility to forage, search, for moths and butterflies. This also gives them the ability to forage for prey (animals eaten for food) in dense forest undergrowth.

SMOKY BATS AND PEOPLE

People have caused the decline of the species in this family due to harming their natural habitats.

BAT RELATIVES

There are no known fossils in this family. In general, bats do not fossilize well because of their small, delicate skeletons. Scientists consider the smoky bats to be most closely related to Central and South American disk-winged bats and funnel-eared bats.

CONSERVATION STATUS

The World Conservation Union (IUCN) Red List categorizes the thumbless bat species as Vulnerable, meaning it is facing a high risk of extinction in the wild. The smoky bat is not considered threatened.

SMOKY BAT (Furipterus horrens): SPECIES ACCOUNT

Physical characteristics: The smoky bat is the smaller of the two species in this family. Head and body length is approximately 1.3 to 1.6 inches (3.3 to 4 centimeters), and their forearms can range from 1.2 to 1.6 inches (3 to 4 centimeters). These bats weigh about 0.1 ounces (3 grams)—only slightly more than the weight of a penny. Females are larger than males by about 10 to 15 percent.

These bats have dense fur. Fur on the head is long and thick. Fur color ranges from brownish gray, dark gray, to a slate blue. Color on the belly is paler. The fur on these bats' head is long and thick. It covers the head and reaches to the snout, almost concealing the mouth. Ears are dark and stiff, and the snout is black.

Geographic range: These bats are found from Costa Rica to southern Brazil, including Venezuela and Colombia. They are also found on Trinidad but they have not been found on any other Caribbean island.

Habitat: These bats live primarily in humid rainforests of Costa Rica south to Brazil. They often live near streams. They have also been found in evergreen forests and clear areas. They have been found in caves, hollows in trees, and beneath rotting logs.

Diet: Smoky bats eat small moths.

Behavior and reproduction: These bats fly slowly and flutter similar to the way moths fly. These bats wait for complete darkness before they leave their roost to begin foraging. They search for prey beneath the forest canopy, at heights ranging from 3.2 to 16.4 feet (1 to 5 meters).

Colony size varies but it appears these bats do group together in relatively large numbers. One colony observed contained fifty-nine individuals. Another found colony contained approximately 250 individuals divided into groups of four to thirty roosting in holes in the walls. In another cave there were 150 bats roosting separately from one other.

Discovered colonies primarily include males, females, and young. Observations have also found there are all-male colonies, suggesting that females may have separate sites to raise their young.

Smoky bats and people: There is no known connection between smoky bats and people.

Conservation status: These bats are not considered threatened. ∎

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. "Smoky Bats, or Thumbless 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.furipteridae.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.

Web sites:

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

Simmons, Nancy. "Furipterus horrens Thumbless Bat." DigiMorph. http://www.digimorph.org/specimens/Furipterus_horrens/whole (accessed on July 5, 2004).

Weinstein, B., and P. Myers. "Family Furipteridae (Smoky Bats and Thumbless Bats." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Furipteridae.html (accessed on July 5, 2004).