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Epomophorus gambianusGambian epauletted fruit bat

By Jamie Cresca

Geographic Range

Gambian epauletted fruit bats, Epomorphorus gambianus are from from Senegal and southern Mali to southern Sudan and Ethiopia, southern Zaire and Tanzia to eastern South Africa. (Wilson and Reeder, 1993)

Habitat

Epomorphorus gambianus occurs in woodland and savannah. It prefers the edges of the forest and roosts in such places as large hollow trees, thick foliage, accumulated roots along stream banks, and below the thatch of open sheds. It is known to roost quite low in trees during the day, undisturbed by the presence of people. It also often roosts where there is considerable light. (Fenton, 1983; Wilson and Reeder, 1993)

Physical Description

Epomorphorus gambianus has a head and body length from 125 to 250 mm. These bats possess a vestigial external tail which is located beneath the interfemoral membrane. The forearm length is usually between 60 and100 mm, and the wingspan in males is about 508 mm. These bats weigh between 40 and 120 g. (Fenton, 1983; Hill and Smith, 1984; Kunz and Racy, 1998; Wimsatt, 1970)

These bats are grayish brown, russet, or tawny in color with a white patch at the base of the ear in both sexes. Males have pouches on their shoulders that contain large patches of white fur. During courtship, males flash these showly white patches to attract mates. Air sacs are also present on the necks of males. (Fenton, 1983; Hill and Smith, 1984; Neuweiler, 2000; Wimsatt, 1970)

The most notable features of E. gambianus are the big, pendulous lips, which often have unusual folds. These lips are expansible, and contribute to the dog-like appearance of the face. Also helping on that front are the simple ears, helping to distinguish these animals from many species of bats. These bats also have a claw on the second finger. (Fenton, 1983; Hill and Smith, 1984; Neuweiler, 2000; Wimsatt, 1970)

  • Sexual Dimorphism
  • sexes colored or patterned differently
  • male more colorful
  • sexes shaped differently
  • ornamentation
  • Range mass
    40 to 120 g
    1.41 to 4.23 oz
  • Range length
    125 to 250 mm
    4.92 to 9.84 in
  • Average wingspan
    508 Males mm
    in

Reproduction

Gambian epauletted fruit bats are polygynous. Males emit mating calls during the breeding season. They will leave the main roost at night and fly to another location. The calls don't seem to have any effects on other males, however, the calls do a good job of attracting females. While making their mating calls, males will flash showy white patches of fur, called epaulets, which are normally concealed. (Fenton, 1983; Neuweiler, 2000)

Epomorphorus gambianus breeds twice annually, with births occurring during the rainy seasons. This meand births peak from April to May and again from October to November. (Fenton, 1983; Kunz and Racy, 1998; Neuweiler, 2000; Wimsatt, 1970)

This species will mate in the late fall and spring. The gestation period is usually about six months. Pregnant females roost apart from the males. There is usually only one young per birth. (Fenton, 1983; Kunz and Racy, 1998; Neuweiler, 2000; Wimsatt, 1970)

Although fertilization ensues immediately after mating, there is little development of the embryo. The delay in embryonic development ensures that birth coincides with a season when food is abundant enough to maintain lactating females, which have a high demand for energy. The delay in embryonic development also permits mating to take place when both males and females are in prime physical condition and have access to good supplies of food. (Fenton, 1983; Kunz and Racy, 1998; Neuweiler, 2000; Wimsatt, 1970)

Newborn E. gambianus grow rapidly, with various parts of their bodies growing at different rates. At birth, the thumbs and hind feet are almost adult in size, and grow very little. However, the forearm and other bones supporting the wing enlarge quickly, producing a wing area in adults that is 10 times the size at birth. (Fenton, 1983; Hill and Smith, 1984; Neuweiler, 2000; Wimsatt, 1970)

Newborns rapidly gain weight until they are weaned. But once they begin to eat fruit instead of their mother's milk, their body weights decrease and they use up the fat reserve they have built up during nursing. At birth E. gambianus is equipped with distinctive milk teeth that appear to be useless as tools for eating solid food, but elp them attach to their mother's teats. The shedding of milk teeth and the emergence of permanent teeth occurs at about the same time as the bats learn to fly and begin to eat fruit. (Fenton, 1983; Hill and Smith, 1984; Neuweiler, 2000; Wimsatt, 1970)

  • Breeding interval
    These bats breed twice yearly.
  • Breeding season
    Breeding occurs in late Fall and Spring.
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    4 to 6 months

Parrental care is primarily given by the mother in this species. Mothers nurse their offspring, although once in a while aunts will also nurse the young. E. gambianus consistently gain weight until they are weaned. Once the switch is made from mothers' milk to fruit, the young start to lose weight. Fortunately, they have a good reserve of fat which they build up while nursing, and this helps to sustain them during the transition to a fruit based diet. (Fenton, 1983)

E. gambianus females carry their young with them, rather than leaving them at the roost when they go our to feed. This probably accounts for two of the rather distinctive features of newborns--their milk teeth and their almost adult sized thumbs and feet. The small bats cling to the nipple with their teeth, and grip their mother's fur with their already large thumbs and hind feet. (Fenton, 1983)

  • Parental Investment
  • no parental involvement
  • altricial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Lifespan/Longevity

These bats have really long lives for being small mammals. Most epauletted fruit bats can live up to 28 years, and average about 21 years. The mechanism for such long life in bats is not known with certainty, but there are some interesting correlations which might explain how bats live so long. Some sources suggest that longevity in bats, in general, is related to the calpain content of neurons. Calpain is a calcium-dependent proteolytic enzyme, one function of which is to break down cytoskeletal proteins. There is apparently a linear negative correlation between calpain activity and life expectancy; and between calpain activity and brain size. Calpain activity has been measured in various regions of the bat brain and found to be seven times less than in the mouse. The bat lives about seven times longer than the mouse. (Fenton, 1983; Hill and Smith, 1984; Neuweiler, 2000; Wilson and Reeder, 1993)

  • Range lifespan
    Status: wild
    28 (high) years
  • Average lifespan
    Status: wild
    21 years
  • Typical lifespan
    Status: wild
    28 (high) years
  • Average lifespan
    Status: wild
    21 years
  • Average lifespan
    Status: captivity
    7.8 years
    AnAge

Behavior

Epomorphorus gambianus roosts in small groups of 6 to 20 individuals; which include young and old of both sexes. Because aunts sometimes nurse their young, we can assume that female kin, at least, sometimes maintain relationships. (Fenton, 1983; Wimsatt, 1970)

Like most megachiropteran bats, this species uses sight rather than echolocation as a means of navigation. It also relies heavily on its sense of smell to help locate fruit. It is a strong flyer, and its flight style is relatively simple. (Fenton, 1983; Wimsatt, 1970)

Home Range

The size of home ranges for this species was not found.

Communication and Perception

As in all mammals, there is probably visual, tactile, accoustic, and scent communication at some point in life. The most well documented part of the communication of this species is what occurs during courtship. During the breeding season, males will leave the main roost at night and fly to another location, where they will begin to emit courting calls. The calls appear to have no effect on the males and attract the females. While calling, the males will display the normally concealed epaulets which are found on their shoulders. They flash the large patches of white fur during courtship to attract mates. Since this occurs at night, it is likely that the white fur is present just because it has the best visibility under the lighting conditions. (Fenton, 1983; Neuweiler, 2000; Wimsatt, 1970)

Food Habits

Epomorphorus gambianus is frugivorous. These bats are likely to appear wherever fig, mango, guava, or banana trees are in fruit. Epomorphorus gambianus is also known for feeding on the nectar of the flowers of Parka clappertoniana in Ghana. (Neuweiler, 2000; Wimsatt, 1970)

  • Plant Foods
  • fruit
  • nectar

Predation

Predators include cats, snakes, and many species of hawks and owls. The most efficient predator is the Bat hawk, which is found in most of Africa and parts of the East Indies. These hawks have large eyes and excellent vision, and usually grab bats in mid-air with their talons, quickly stuffing them into their large mouths. Other predators consist of other bats, occasionally young fruit bats fall prey to large slit-faced bats and heart-nosed bats. (Kunz and Racy, 1998; Neuweiler, 2000; Wimsatt, 1970)

Ecosystem Roles

Epomorphorus gambianus droppings support whole ecosystems of unique organisms, including bacteria useful in detoxifying wastes, and producing gasohol. This species also aids in seed dipersal in such agricultural plants as bannanas, mangoes, dates and figs. When feeding on nectar, these bats probably aid in pollination. As a prey species, E. gambianus probably has some affect on predator populations. (Findley, 1993; Neuweiler, 2000; Wimsatt, 1970)

  • Ecosystem Impact
  • disperses seeds
  • pollinates
  • creates habitat

Economic Importance for Humans: Positive

Many important agricultural plants, like bananas, breadfruit, mangoes, cashews, dates, and figs rely on E. gambianus for pollination and seed dispersal. (Findley, 1993; Neuweiler, 2000)

  • Positive Impacts
  • pollinates crops

Economic Importance for Humans: Negative

Epomorphorus gambianus eats a lot of fruit, and is known to cause significant damage to orchards. This is sort of ironic, since the animals are also needed to pollinate these crops. (Wimsatt, 1970)

  • Negative Impacts
  • crop pest

Conservation Status

Populations of E. gambianus may be threatened by pesticides on fruit, human disturbance, and over-collecting in the past. However the number one reason it may be threatened is habitat destruction. All bats are protected under the Wildlife Act, 1975. This means bats cannot be collected or handled without a permit. (Hill and Smith, 1984; Wimsatt, 1970; Findley, 1993)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Jamie Cresca (author), University of Wisconsin-Stevens Point, Chris Yahnke (editor), University of Wisconsin-Stevens Point.

Glossary

Ethiopian

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

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

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

embryonic diapause

At about the time a female gives birth (e.g. in most kangaroo species), she also becomes receptive and mates. Embryos produced at this mating develop only as far as a hollow ball of cells (the blastocyst) and then become quiescent, entering a state of suspended animation or embryonic diapause. The hormonal signal (prolactin) which blocks further development of the blastocyst is produced in response to the sucking stimulus from the young in the pouch. When sucking decreases as the young begins to eat other food and to leave the pouch, or if the young is lost from the pouch, the quiescent blastocyst resumes development, the embryo is born, and the cycle begins again. (Macdonald 1984)

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.

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

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.

nocturnal

active during the night

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

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

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Fenton, B. 1983. Just Bats. Toronto, Canada: University of Toronto Press.

Findley, J. 1993. Bats A Community Perspective. Great Britain: Cambridge University Press.

Hill, J., J. Smith. 1984. Bats, A Natural History. Austin: University of Texas Press.

Kunz, T., P. Racy. 1998. Bat Biology and Conservation. London: Smithsonian Instituition Press.

Neuweiler, G. 2000. The Biology of Bats. New York: Oxford University Press.

Wilson, D., D. Reeder. 1993. Mammal Species of the World, A Taxonomic and Geographic Reference. Washington: Smithsonian Institution Press.

Wimsatt, W. 1970. Biology of Bats. New York: Academic Press.

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