Epomophorus wahlbergiWahlberg's epauletted fruit bat

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Geographic Range

The Walberg's epauletted fruit bat can be found in Africa, anywhere south of the Sahara desert. These bats live in woodland and savannah areas, and prefer the edges of forests. During the summer, they migrate in large numbers to Taaween, in the Zoutpansberg district of South Africa, attracted by the ripening crop of guavas.

Habitat

During the day, they live in hollow trees, underneath large leaves, and beneath the eaves of buildings. They often roost where there in considerable light. Every few days, they will move to a new roosting site. They roost in small groups containing mixed ages of males and females, the size of which range from three to one hundred individuals. They often choose the same spot to roost, at certain times of the year, for many consecutive years. While hanging from their feet in their roosts, they will isolate themselves from their neighbors by short distances. While roosting, they remain relatively quiet, and do not move very much. They make it a point to not intrude on each other's space.

Physical Description

Wahlberg's epauletted fruit bats are volant creatures. They have a prominent keel on their sternum, which supports the flight muscles. The total body length is between 125mm and 250mm long, and the wing span in males is about 508mm. They weigh between 40 grams and 120 grams. Both the first and second digits of the foreleg are clawed. The face and head resembles that of a dog.

These bats are grayish brown, russet, or tawny in color. Air sacks are present on the necks of males. These sacks are used in food collection, and may aid in creating a megaphone effect of the calls used by males to attract females during courtship. The males have shoulder epaulets that are used in courtship displays.

White spots of fur are located at the top part of the base of the ear in both sexes. Scent glands are located at the places where the white ear spots and shoulder epaulets are found. The ear is simple and oval, forming an unbroken ring, with no tragus. These bats do not have a nose leaf. The tail is short, and sticks out of the uropatagium, which is very narrow in this species. They have a simple wing, when compared to other bat species. They are strong fliers, and travel as far as ten kilometers to find food. Their eyes are very large. Sight, as well as smell, are what these bats use most often to locate their surroundings. Their jaws are strong, and their teeth are adapted to a fruit diet. The cheek teeth are large and flat, just the right surface for chewing fruit.

  • Range mass
    40 to 120 g
    1.41 to 4.23 oz

Reproduction

During the breeding season, the males use the shoulder epaulets as a part of courtship. This courtship behavior is called an arena, or Îlekâ, mating system. The males congregate at traditional sites, where they puff up their white shoulder patches, and begin using mating calls, in an attempt to get passing females to select them. The call used by the males to attract females combines four short chirps that range from 2.0 kHz to 7.5kHz, and is one second in duration.

Young are born singly, in most cases, but twins are occasionally seen. As she forages for food, the mother caries her offspring clinging to her chest. Females have one pair of mammae located on the chest. The male sexual organ resembles that of some primates. Mating occurs twice per year on a seasonal basis, with births occurring around the end of February, and the beginning of September. Gestation lasts from five to six months. Females are the only ones who rear the young. The males don't give assistance. Other bats from the same family, (Pteropus poliocephalis, Pteropus giganteus, and Rousettus aegyptiacus), recognize their young through vocalizations and olfaction. They nurse their own young, and do not scent mark them. By inference, it is assumed that the Walberg's epauletted fruit bat does the same for its young.

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Average number of offspring
    1
    AnAge

Lifespan/Longevity

  • Average lifespan
    Status: captivity
    10.1 years
    AnAge

Behavior

Being able to get fruit from trees was probably what caused these bats to evolve into flight. They appear to keep track of the ripening of the fruit of a particular tree, or stand of trees. Once the fruit ripens, they group together in the tree for several nights, and eat the ripened fruit. They often completely strip the tree of all of its fruit. These bats are active mostly in the evening and at night, but have been observed flying in the daytime.

Communication and Perception

Food Habits

These bats are frugivorous. They chew the fruit, swallow the juice, and spit out most of the pulp and seeds. They swallow some of the softer pulp, and some of the seeds. The swallowed food goes through the simple digestive tract, usually within a half an hour. They use several methods to get the fruit from the tree. 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 of 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 on figs, mangoes, guavas, bananas, peaches, apples, papayas, 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, as well.

Economic Importance for Humans: Positive

The seedlings of most tropical plant species 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 found. Fig seeds will not germinate unless the seeds pass through the digestive tract of a bat, or bird. These bats are an important agent of seed dispersal in the tropics. Although bats may at times be local pests of fruit crops, their value in the preservation of the rain forests, is critical. These bats travel to areas where the seeds in their droppings help to expand the rain forest acreage. These bats pollinate baobab (Adansonia digitata), an economically important tree in the African savannah.

Economic Importance for Humans: Negative

Control measures, in the form of poisoned fruit for bait, are sometimes utilized in areas where they feed extensively on cultivated fruit.

Conservation Status

This species is in jeopardy from the human destruction of tropical forests. The practice of bat-banding also threatens their existence, if the banding injures the delicate flight membranes, and if the banding causes stress to the bat. The public's attitude toward bats needs to change, in order for these animals to survive. Education is the key toward changing the misconceptions that many people have. Bats are a unique and irreplaceable value to man and the ecosystems of the earth.

Other Comments

The Wahlberg's epauletted fruit bat may be one of four species of Megachiropterans that use echolocation to partially orient themselves. These sounds are mostly audible, but have ultrasonic components. The sounds are not produced in the larynx, but are made by a clicking of the tongue on the back of the throat. The tragus and nose leaves are used by echolocating bats to orient themselves. The Wahlberg's epauletted fruit bat does not have these structures, because it orients itself mostly by sight and scent.

Bats molt once a year. Males and non-reproducing females molt in late spring. Reproductive females will not molt until after the young are weaned, presumably to prevent energy depletion during the time of lactation. The annual molt usually follows a specific pattern. On the dorsal surface, the molt starts at the top of the head. On the ventral surface of the body, the molt begins at the throat. From these initial areas, the molt spreads to all other parts of the body. In other mammals, the new coat of hair is usually well developed before the old hair starts to fall out, or is shed in patches. In the few bats that have been studied, the old hairs apparently drop out, as new hairs grow into place. Therefore, there is usually no outward sign that the bat is molting. This could be beneficial to the bats, because variation in pelage pattern could affect flight capabilities, by having a negative effect on air movement over the body of the bat.

Contributors

Barbara Lundrigan (author), Michigan State University, Hannelore Grome (author), Michigan State University.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

References

Allen, G. 1967. Bats. Dover Publication, Incorporated..

Fenton, M. 1985. Communication in the Chiroptera. Indiana University Press..

Fleming, T. 1988. The Short-Tailed Fruit Bat. Chicago: University of Chicago Press.

Hill, J., J. Smith. 1984. Bats: A Natural History. London: British Museum.

Nowak, R. 1994. Walker's Bats of the World. Baltimore: John Hopkins University Press.

Schober, W. 1984. The Lives of Bats. Croom Helm, Limited.

Wimsatt, W. 1970. Biology of Bats. Academic Press, Incorporated.