HORSESHOE BATS: Rhinolophidae

PHYSICAL CHARACTERISTICS

The name "horseshoe" bats comes from the distinctive shape of their nose. Many species of bats have fleshy folds of skin around their nostrils called a noseleaf. In the horseshoe bats, the lower part of its noseleaf is shaped like a horseshoe or a U-shape. This lower section covers the bat's upper lip. The upper part of the noseleaf, above the nostril, is pointed. In some species, such as Hildebrandt's horseshoe bat, the noseleaf is hairy.

Horseshoe bat species range widely in size, from small to moderate. The smaller species of these bats can have a head and body length of 1.4 inches (3.5 centimeters) and the larger species can measure 4.3 inches (11 centimeters). They weigh from 0.15 ounces (4.3 grams; less than the weight of two pennies) to 13.8 ounces (35 grams).

The fur on horseshoe bats can be a variety of colors, including gray-brown and reddish brown fur. Other bats can have gray, black, dark brown, yellow, or bright orange-red fur. Their fur is long and soft. These bats have large ears that are typically pointy and can move independently of one another. Their eyes are relatively small. The wings are broad with rounded ends.

GEOGRAPHIC RANGE

Horseshoe bats are found in temperate (areas with moderate temperatures) and tropical regions of the Old World, meaning the part of the world made up of Australia, Africa, Asia, and Europe. These bats are found in southern Europe, Africa, and southern Asia to northern and eastern Australia, including many Pacific islands. They do not live in the arid (extremely dry) ranges of Africa. In many areas, these bats have extremely small ranges.

HABITAT

Horseshoe bats live in a wide variety of areas, such as forests, savannas, open areas, and occasionally in deserts. Horseshoe bats can live in areas that are cooler than many other bats can survive. They also have a wide variety of places in which they roost, meaning rest or settle. Primary roosting sites include caves and hollow trees. Other roosting sites include buildings, houses, mines, holes, and tunnels. Some of these bats roost in open areas. Research indicates that the roosting sites for these bats may be important factors in determining where they decide to live.

DIET

Horseshoe bats eat insects and spiders.

BEHAVIOR AND REPRODUCTION

Like all bats, horseshoe bats are nocturnal, meaning they are active at night. They begin foraging for their food later in the evening than most other bats, typically hunting about 20 feet (6 meters) above the ground. Horseshoe bats have a fluttering or hovering flight. These bats will catch prey (animals hunted for food) both in flight and on surfaces, such as leaves or branches. Some species also sit on some type of perch, such as a branch, and snatch insects as they fly past. When foraging, or searching, for food on surfaces, called gleaning, these bats find prey on branches, leaves, rocks, and the ground. The bats will eat the insect in flight if they are small enough. If the prey is a large insect, they may take their prey back to a roost or a feeding perch. They can catch the insect in their wings and store it in their cheek.

To locate their prey, horseshoe bats use echolocation (eck-oh-loh-KAY-shun), a technique in which they send out sounds and listen to the sounds that bounce back to locate objects. Horseshoe bats echolocate through their noses, as opposed to most bats, which send out echolocation calls through their mouths. Using echolocation, horseshoe bats can detect the flutter of insects' wings.

Most species gather together to roost, from small colonies of about twenty individuals, to large colonies of up to 2,000 individuals. One species in particular, the woolly horseshoe bat, roosts in pairs. These bats hang freely when they roost, not huddling next to one another to keep warm as do many other bats. When roosting, these bats wrap their wings around themselves, enclosing their entire body.

Species that live in northern areas may hibernate (deep sleep in which an animal conserves energy) during the winter. Other species go into torpor every day. Torpor is a period of inactivity in which an animal's heart rate slows down to conserve energy. At least one species is migratory, meaning they travel to warmer areas when the weather becomes cool. Many species that hibernate can awaken easily and change their hibernating sites occasionally, sometimes flying almost a mile (1,500 meters) or more to a new place.

In some species, including ones that hibernate, females mate during the fall, but fertilization does not occur until the spring. In other species, mating and fertilization occur in the spring. For bats that live in tropical areas, females give birth during the warm summer months. In some species, males and females live together all year, while females form separate colonies in other species. Gestation (pregnancy) ranges from seven weeks to slightly over five months. Bats typically have one offspring per season, and the babies are independent at six to eight weeks of age.

HORSESHOE BATS AND PEOPLE

People have caused the decline in many species of horseshoe bats by destroying their habitat. Altering or disturbing these bats' habitat can indirectly reduce their prey. The use of insecticides, a chemical used to kill or control insects, has also reduced the population of the bats' prey.

SPECIES RECOVERY

With a population that has dwindled down to an estimated 5,000 individuals, the greater horseshoes are one of England's most rare bats. Concerned about extinction, the country has taken steps to help this species once again flourish. In 1998 the English Nature Greater Horseshoe Bat Project was launched with the prime goal to increase the species population by 25 percent by the year 2010. With awareness, education, and specially designated roosting sites, the number of recorded births in 2003 had reached record levels (228). Warmer winters and a reduction in the use of chemicals and pesticides in farming also contributed to population growth.

CONSERVATION STATUS

Most species of horseshoe bats are in danger of a decline in population or have already experienced population loss. Researchers know little about some species of these bats and so their conservation status is not known. Out of the species listed in the IUCN Red List, thiry-eight species, there is one species listed as Critically Endangered, facing an extremely high risk of extinction, dying out, in the wild; and two as Endangered, facing a very high risk of extinction in the wild. There are also species that are not considered endangered globally but are in danger of extinction in specific areas, such as the greater horseshoe bat, which is regarded as endangered in Europe.

GREATER HORSESHOE BAT (Rhinolophus ferrumequinum): SPECIES ACCOUNTS

Physical characteristics: The greater horseshoe bats are among the largest species of its family. The length of their head and body combined ranges from 2.2 to 3.1 inches (5.6 to 7.9 centimeters), and its wingspan is from 13.8 to 15.6 inches (35 to 40 centimeters). These bats have large, pointed ears, small eyes, and a flattened face, with a distinct horseshoe-shaped fleshy disc nose. Fur is fine and silky, typically light brown to grayish, with a reddish color. The wings and ears are light gray. Offspring are born gray and turn reddish brown as they grow.

Geographic range: Greater horseshoe bats are found in southern Europe, Great Britain, India, and southern Asia to southern China and Japan. In the United Kingdom they are primarily found only in southwest England and south Wales.

Habitat: These bats live in forest, as well as open land, such as pastures. They roost in caves, mine tunnels, and large buildings.

Diet: Greater horseshoe bats eat small- to medium-sized insects, including beetles, moths, and flies.

Behavior and reproduction: With their broad wings, greater horseshoe bats fly slowly. These bats can feed by flying low to the ground and catching prey in flight. They also can wait for their prey on a perch, snatching the insect as it passes. They take large prey to a regular feeding perch.

Greater horseshoe bats emerge from their roosts about half an hour before sunset. Between warmer months, May to August, they typically return to their roost after about an hour and remain there until they emerge for a second round of foraging at about dawn. From late August until May they may remain at their roost all night.

Greater horseshoe bats hibernate. They may start hibernating near the entrance of caves, then move to sites deeper within the cave as the weather becomes cooler. The moistness of the caves prevents the bats from losing too much water from their bodies.

Greater horseshoe bats breed in autumn, from September to October, and give birth from June to July (where they've been studied in Europe). Females give birth to one young, after a gestation period of about seventy-five days. The mother hangs upside down while giving birth and the infant is born into her overlapped wings. They can live for up to thirty years.

Greater horseshoe bats and people: People have caused the decline of the greater horseshoe bats by disturbing or destroying their roosts and prey (with pesticide use). In Great Britain, it is estimated that the greater horseshoe bat population has decreased by 90 percent since 1900.

Conservation status: The IUCN Red List classifies the greater horseshoe bat as Near Threatened, meaning it is not yet threatened, but could become so, around the world. But in some areas, such as Europe, this species is considered endangered by national or regional conservation groups. ∎

CAPE HORSESHOE BAT (Rhinolophus capensis): SPECIES ACCOUNTS

Physical characteristics: The cape horseshoe bat is small to medium in size, with a head and body length of about 2.4 inches (6.2 centimeters). Its fur on the upper side and wings are dark brown, the back is lighter brown and the underside is brown to cream in color. It has the distinctive horseshoe ring around the nose, with a large, wavy triangular leaf extending from the horseshoe up between the eyes.

Geographic range: Cape horseshoe bats are found along the coastline of southern Africa.

Habitat: Cape horseshoe bats live along the coast. They are found in coastal and sea caves.

Diet: Cape horseshoe bats eat mainly beetles.

Behavior and reproduction: These bats catch their prey while flying slowly and low to the ground. They also can hunt from perches, waiting for prey to pass. When roosting, they usually hang individually, rather than in dense clusters.

They mate in spring, August through September, and young are born from November to December.

Cape horseshoe bats and people: There is no known, significant relationship between these bats and people.

Conservation status: The IUCN lists the cape horseshoe bat as Vulnerable. ∎

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. "Horseshoe 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.rhinolophidae.rhinolophus.html (accessed on July 5, 2004).

Raabe, Emily. Horseshoe Bats. New York, NY: Powerkids Press, 2003.

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

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

Periodicals:

Griffin, Donald R. "Return to the Magic Well: Echolocation Behavior of Bats and Responses of Insect Prey." BioScience (July, 2001): 555.

"Horseshoe Bats Sound Out the Choicest Prey." New Scientist (March, 2003): 36.

Thi Dao, Nguyen. "My Life as a Forest Creature: Growing Up with the Cuc Phuong National Park. (This Land)." Natural History (March, 2003): 70.

Web sites:

"Bats in Australia." Australian Museum. http://www.amonline.net.au/bats/records/bat15.htm (accessed on July 5, 2004).

Myers, Phil. "Family Rhinolophidae (Horseshoe Bats and Old World Leaf-Nosed Bats)." Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Rhinolophidae.html (accessed on July 5, 2004).

Roberts, G. M., and A. M. Hutson. "Greater Horseshoe Bat: Rhinolophus ferrumequinum The Bat Conservation Trust. http://www.bats.org.uk/batinfo/gr_horse.htm (accessed on July 5, 2004).

"Greater Horseshoe Bat." BBC Science and Nature: Animals. http://www.bbc.co.uk/nature/wildfacts/factfiles/284.shtml (accessed on July 5, 2004).

"Greater Horseshoe Bat: Rhinolophus ferrumequinum." UK Biodiversity Action Plan. http://www.ukbap.org.uk/ukplans.aspx?ID=550 (accessed on July 5, 2004).