Species Account

Wahlbergπs Epauletted Fruit Bat

Epomophorus wahlbergi

Wahlbergπs epauletted fruit bat, or Epomophorus wahlbergi, is a megabat, thus is of the suborder Megachiroptera and the Pteropodidae family (Corbett 1986). Many observers note that the head of Wahlbergπs epauletted fruit bat resembles that of a dog, and most relate it to the head of a dachshund. However, the skeletal structure of Wahlbergπs epauletted fruit bat reflects the primary function of the bat. The prominent keel on their sternum, or chest bone, supports the major muscles used in flight. The muscles attached to this keel are very powerful and are responsible for the swift movements of the long wings. This is important for the survival of these bats, for they often travel as far as ten kilometers to find food. The wingspan of Wahlbergπs epauletted fruit bat is about 508mm. This is relatively long, for the total body length is usually between 125mm and 250mm long, making the wingspan double or even triple the total body length. Wahlbergπs epauletted fruit bats usually weigh between 40 and 120 grams (Kingdon 1974a). Compared to other bat species, Wahlbergπs epauletted fruit bats have a simple wing structure. However, both the first and the second digits of the foreleg are clawed.

Wahlbergπs epauletted fruit bats are found in a variety of colors, the most common being grayish brown, russet, or tawny in color (Nowak 1994). These bats are named from the long tufts of white fur, or epaulets, that sprout from their shoulders. Males use their shoulder epaulets to attract females in courtship displays. Males also differ in appearance from females, for males have air sacs in their necks. These sacs are used in food collection, as well as aid in amplifying calls used to attract females during courtship (Nowak 1994). However, both sexes have white spots of fur located at the top of the base of the ear. Located where the white ear spots and the shoulder epaulets are found, Wahlbergπs epauletted fruit bats have scent glands. These glands produce a unique odor that allows the bats to recognize one another.

The ear in Wahlbergπs epauletted fruit bats is simple, for the outer ear has a basic oval shape, forming an unbroken ring. The ear also lacks a tragus. As does the ear, the nose of Wahlbergπs epauletted fruit bat has a simple structure. These bats do not have a nose leaf, for they do not rely totally on echolocation to navigate. Therefore, Wahlbergπs epauletted fruit bats have very large eyes. They must rely heavily on their sight, as well as smell, to navigate and identify their surroundings. Due to their frugivorous diet, their jaws are strong, and their teeth are adapted to best process this fruit. Their cheek teeth are large and flat, creating the perfect surface for chewing tough fruit. Though they do not rely totally on echolocation to navigate, the Wahlbergπs epauletted fruit bat may be one of the four species of Megachiropterans that use echolocation to partially orient themselves. Unlike other echolocating bats, the sounds that these bats use are mostly audible to humans, but do have ultrasonic components. Also unlike other echolocating bats, the sounds are not produced in the larynx, but are made by a clicking of the tongue on the back of the throat (Lovett 30).

Wahlbergπs epauletted fruit bat is native to Africa, and is found anywhere south of the Sahara desert (Meester 1977). However, the largest populations are in Cameroon and Somalia south to South Africa. Though these bats live in woodland and savannah areas, they prefer the edges of forests (Kingdon 1974a). Summer brings a large migration to Taaween, an area in the Zoutpansberg district of South Africa (Thomas 1983). The ripening crop of guavas attracts these bats by the thousands.

During the daylight hours, Wahlbergπs epauletted fruit bats live in hollow trees, underneath large leaves, and beneath the eaves of buildings. They often are found roosting where there is considerable light. Every few days, they will relocate to a new roosting site (Fenton et al. 1985). They roost in small groups containing mixed ages of both males and females. The size of these groups range from a few individuals to about one hundred individuals, depending on the size of the roosting area (Wickler and Seibt 1976). They often revisit their previous roosting spots, at certain times of the year, for many consecutive years. When roosting, they do not pack themselves tightly next to one another; they will isolate themselves from their neighbors by short distances, all while hanging from their feet in their roosts. While roosting, they remain relatively quiet, and movement is at a minimum. These bats seem to have a respect for each other, for they make it a point to not intrude on each otherπs space.

As aforementioned, males use their shoulder epaulets as a part of courtship. During the breeding season, the males congregate at traditional sites, where they puff up their white shoulder patches, puff out their cheek pouches, fan their wings and make repeated gonglike calls to attract a mate, all in an attempt to get passing females to select them. The calls the male bats use to attract females combines four short chirps, and is one second in duration. The pouches in the malesπ cheeks are inflatable sacs that act as a resonance chamber to enhance their calls. The males also use their long tufts of hair and beating wings to help waft glandular odors that are attractive to cruising females. The mating procedures are extensive, all night events. An unusual aspect of this mating procedure is that the females apparently need light to see the malesπ courtship dance. Research shows that Wahlbergπs epauletted fruit bats in Kenyan towns utilize the fabricated light from streetlamps in Kenyan towns to provide sufficient light to allow males to court all night long, even on moonless nights.

In most cases, Wahlbergπs epauletted fruit bats bear a single young, but twins are occasionally seen. After giving birth, the mother carries her offspring clinging to her chest, as she forages for food. Females have one pair of mammary glands located on the chest, from which they nurse their young. The male sexual organ resembles that of some primates. Wahlbergπs epauletted fruit bats mate twice per year on a seasonal basis, with births occurring around the end of February, as well as the beginning of September (Bergmans 1979a). Gestation lasts from five to six months. When the offspring are born, females are the only ones who rear the young, for the males do not give assistance. Wahlbergπs epauletted fruit bats do not scent mark their young, they recognize their own young through vocalizations and olfaction.

Wahlbergπs epauletted fruit bats are frugivorous, as indicated by their common name. The process by which they consume the fruit is somewhat unique. They chew the fruit, swallow the juice, and spit out most of the pulp and seeds. They swallow some of the softer pulp, as well as some of the seeds. The swallowed food goes through their simple monogastric digestive tract, usually within half an hour. In order to get the fruit from the tree, these bats have several methods. They either bite the fruit while hovering; or they hang from a branch with one foot while using the other foot to hold the fruit while they eat it; or they chop the fruit from a branch by holding the fruit in their mouths, and making a twisting motion in flight until the fruit drops off the stem. The structure of their lips and windpipe creates suction that helps them to suck the juices from softer parts of the fruit. They also chew flowers to get the nectar and juices. They feed mainly on figs, mangoes, guavas, bananas, peaches, papayas, apples, and small berries. The smell of ripening fruit is what attracts them to their food source. Fruits are nutritious because they contain high quantities of carbohydrates. Many fruits contain fats, which are of benefit to the bat, in addition to the carbohydrates.

Due to its frugivorous diet, the Wahlbergπs epauletted fruit bat is a vital element in seed dispersal in the tropics. The seedlings of most tropical plants will not grow and mature in the shade of the parent plant. Therefore, the seeds must be carried beyond the area where the parent plants are located. To add to that, fig seeds will not germinate without first passing through the digestive tract of a bat or bird. Although many see bats as the local pests of the fruit crops, they are invaluable in the preservation of the rain forests (Tuttle 557). After ingesting the seeds of various fruits, these bats travel to areas where the seeds in their droppings help expand the rain forest acreage.

However, this species is in jeopardy from the perpetual human destruction of rain forests. As humans wipe out the tropical rain forests of the world, these bats are forced to find new homes, often ones closer to towns and cities. This relocation poses a problem, for control measures, in the form of poisoned fruit, are sometimes utilized in areas where the feed extensively on cultivated fruit. Humans pose yet another threat to bats. As we try to learn more about these creatures, we continue to threaten their existence. The practice of bat banding is becoming dangerous to many species of bats. If the banding injures the delicate flight membranes, or even if the banding causes stress to the bat, the batπs survival is threatened. In order for these animals to survive, the public conception of bats must be permanently changed. Bats are a unique and irreplaceable value to man and the ecosystems of the earth.

Works Cited

Bergmans, W. 1979a. Taxonomy and zoogeography of the fruit bats of the People's Republic of

Congo, with notes on their reproductive biology (Mammalia: Megachiroptera). Bijdragen

Tot de Dierkunde. 161-86pp.

Corbet, G. B. 1986. A world list of mammalian species. British Mus. (Nat. Hist.), London,

254 pp.

Fenton, M. B. 1975. Observations on the biology of some Rhodesian bats, including a key to the

Chiroptera of Rhodesia. Ontario Mus. Life Sci. Contrib., no. 104, 27 pp.

Kingdon, J. 1971a. East African mammals. An Atlas of Evolution in Africa. London: Academic

Press. 341pp.

Lovett, Sarah. ≥Wahlbergπs Epauletted Bat (Epomophorus wahlbergi).≤ Extremely Weird Bats.

New Mexico: John Muir Publications. 30.

Meester, J. 1977. The mammals of Africa: an identification manual. Smithson. Inst. Press,

Washington, D.C. 37pp.

Nowak, R. 1994. Walkerπs Bats of the World. Baltimore: Johns Hopkins University Press. 66pp.

Thomas, D. W. 1983. The annual migrations of three species of West African fruit bats

(Chiroptera: Pteropodidae). Can. J. Zool. 2266-72pp.

Tuttle, M. ≥Gentle Fliers of the African Night.≤ National Geographic. Apr. 1986: 540-558.

Wickler, W., and U. Seibt. 1976. Field studies of the African fruit bat Epomophorus wahlbergi,

with special reference to male calling. Tierpsychol. 345-76pp.