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Micropteropus pusillusPeters's dwarf epauletted fruit bat

By Judith Wan

Geographic Range

Micropteropus pusillus, the dwarf epauleted bat, has an Ethiopian distribution. It occurs in western, southwestern, and central Africa. The northern boundary of its range is set by the Sudanian and Ethiopian highlands, the eastern boundary is set by the Ethiopian highlands. The southern limit of the range is within the North Zambesian woodland. Micropteropus pusillus is found in Senegal, southern Sudan and Ethiopia, and south to Angola and southern Zaire. (Nowak, 1999)

Habitat

Micropteropus pusillus occurs in a variety of habitats. It is commonly found in savannah woodlands, vegetation that fringes forests, and coastal areas. It also inhabits swamp forests, grasslands, and bushlands. (Jones, 1971; Owen-Ashley and Wilson, 1998)

Micropteropus pusillus prefers to roost in dense vegetation. Roosts are located 3 to 6 meters above the ground shrubs or in the lower parts of trees. (Jones, 1972; Marshall and McWiliam, 1982)

  • Range elevation
    50 to 800 m
    164.04 to 2624.67 ft

Physical Description

Micropteropus pusillus is one of the smaller members of the suborder Megachiroptera. On the bat's dorsal surface, the pelage is varying shades of brown and moderately long and thick. Hair on the ventral surface is more sparse, shorter, and of lighter tone. The pelage is soft, covering the upper arm and part of the forearm, and extends onto the wing. Small white to yellowish colored tufts of hair are present at the base of the ears.

In appearance, M. pusillus resembles pteropodids of the genus Epomophorus, except the lips are not as expansible, and the muzzle and ears are shorter. It has a round head and large eyes, and ears that are rounded at the tip. The tail is usually imperceptible in the uropatagium. (Marshall and McWiliam, 1982; Nowak, 1999)

Micropteropus pusillus exhibits secondary sexual dimorphism. Adult males have epaulettes, which are tufts of white hairs that grow within shoulder pouches (circular pocket-like folds of skin). The hairs can be held erect to form a white rosette. Adult females lack epaulettes, but they have shallow pouches that resemble those of sub-adult males.

On average, females are slightly larger than males. The average weight of males is about 20 grams, while the average weight of females is 22 grams. The forearm length ranges from 49 to 53 mm in males, and 50 to 56 mm in females. (Marshall and McWiliam, 1982; Nowak, 1999; Owen-Ashley and Wilson, 1998)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Range mass
    24 to 34 g
    0.85 to 1.20 oz
  • Range length
    67 to 105 mm
    2.64 to 4.13 in

Reproduction

Little is known about the mating behavior and system of M. pusillus.

Micropteropus pusillus is bimodally polyestrous. It has two birth periods per year, from March to May and from September to November. These periods are adjusted so that lactation coincides with the rainy season and availability of fruit. Each parturition period is followed by a post-partum estrus and then by immediate embryonic development.

Breeding occurs throughout much of the year but mostly in March, April, May, and November. The gestation period is five or six months. Weaning takes from 7 to 13 weeks. (Jones, 1972; Nowak, 1999; Thomas and Marshall, 1984)

Females are able to mate at six months, and give birth when they are eleven to twelve months old. Sub-adult males have testes less than 3 mm in length and underdeveloped epaulettes. Males reach puberty at 7 months and are fully mature by 9 months. (Owen-Ashley and Wilson, 1998; Thomas and Marshall, 1984)

Growth rates for juvenile bats are the same for both sexes, although females achieve greater adult size than males. The mean growth rate for juvenile bats is about 116 milligrams per day. This slow rate is accounted for by the low protien content of their diet. (Thomas and Marshall, 1984)

Males have enlarged vocal cords and emit a shrill ringing call. The opening and vibrating of the shoulder epaulettes in males serve to attract females. Male displays like those in the genus Epomophorous are also present. (Owen-Ashley and Wilson, 1998)

  • Breeding interval
    Micropteropus pusillus breeds twice a year.
  • Breeding season
    March-May, November
  • Range gestation period
    5 to 6 months
  • Range weaning age
    7 to 13 weeks
  • Average time to independence
    9 months
  • Range age at sexual or reproductive maturity (female)
    6 to 12 months
  • Range age at sexual or reproductive maturity (male)
    7 to 9 months

Parental investment in M. pusillus is undocumented. However, young are known to roost with their mothers, implying that parental care is skewed towards the females of the species.

Lifespan/Longevity

The lifespan of M. pusillus is undocumented.

Behavior

Micropteropus pusillus usually roosts alone or in twos, but may be found in groups of up to ten. Breeding pairs or pregnant females and young may roost together. When roosting, the wings are wrapped around the body and across the face. The eyes are closed, but the ears remain erect.

Unless disturbed, M. pusillus spends most of the day and night roosting. It wakes just after dusk and forages until about midnight, when it returns to the roost. (Jones, 1972; Thomas and Marshall, 1984)

Foraging is done at low heights. Feeding is done in one of two ways. The bat may land upright on the fruit and remain there for a few minutes, or it may hover in front of the fruit and take a bite. Food is masticated for about thirty seconds by a slow sucking action of the lips and mouth. Juice and pulp from the fruit are ingested, while the rest is spit out in the form of dry pellets. Food is handled with the mouth, thumbs, and feet. Micropteropus pusillus may also take food items to a feeding perch. (Marshall and McWiliam, 1982; Owen-Ashley and Wilson, 1998)

Home Range

The home range size of M. pusillus is undocumented. This species is not migratory and returns to the same roost after feeding.

Communication and Perception

Like most bats in the family Pteropodidae, M. pusillus does not rely on echolocation as a mode of perception. Instead, this bat relies mostly on sight and sound to percieve its environment and communicate. Males have enlarged vocal cords for emitting shrill calls. Males also open and vibrate their shoulder epaulettes to attract females. (Owen-Ashley and Wilson, 1998)

Food Habits

Micropteropus pusillus is fruigivorous and nectarivorous. The fruits of Ficus capensis and F. vallischoudae comprise a large part of the diet. Also eaten are fruits from Anacardium occidentale, Annona chrysophila, and Psidium guajava. This bat also feeds on fallen fruit, and often visits mango groves and banana plantations.

Micropteropus pusillus also eats flowers, pollen, and nectar from Kigelia pinnata (the sausage tree), K. africana, Spathodea campanulata, Adansonia digitata, Maranthus polyandra, and Parinari polyandra. ("Bat Conservation International- Flying Foxes and Food", 2003; Owen-Ashley and Wilson, 1998)

  • Plant Foods
  • fruit
  • nectar
  • pollen
  • flowers

Predation

There are no known predators on M. pusillus. In general, predators on bats include owls, snakes, and occasionally other bats.

Ecosystem Roles

Micropteropus pusillus is one of the species that pollinates the flowers of Kigelia pinnata, the sausage tree. The flowers open at dusk and emit an unpleasant odor that attracts the bat. Sausage tree flowers hang on thick stalks and have deep floral cups. The male and female parts of the flower are confined to the basal region. The bat lands on the lip of the flower and pushes its head into the floral cup to drink nectar, thereby covering its head and shoulders with pollen. The flowers close at about 11pm, when the bat is no longer present. Micropteropus pusillus may also pollinate flowers of other species of plants. (Owen-Ashley and Wilson, 1998)

  • Ecosystem Impact
  • pollinates

Economic Importance for Humans: Positive

Because M. pusillus is a pollinator of Kigelia pinnata, the sausage tree owes at least part of its continued existence to the bat. This is of importance for humans interested in preserving biodiversity. (Ayensu, 1974)

Economic Importance for Humans: Negative

Micropteropus pusillus, like other fruigivorous bats, can be a nuisance to humans. In some areas, fruit crops are damaged by bats during feeding. (Ayensu, 1974)

  • Negative Impacts
  • crop pest

Conservation Status

Micropteropus pusillus is not listed on the CITES appendices or the United States Endangered Species Act list. On the IUCN Red List, M. pusillus is listed as Lower Risk/Least Concern (LR/lc).

Contributors

Matthew Wund (editor), University of Michigan-Ann Arbor.

Judith Wan (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Ethiopian

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

World Map

acoustic

uses sound to communicate

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

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.

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.

nectarivore

an animal that mainly eats nectar from flowers

nocturnal

active during the night

seasonal breeding

breeding is confined to a particular season

sexual

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

solitary

lives alone

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

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.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

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

2003. "Bat Conservation International- Flying Foxes and Food" (On-line). Accessed March 17, 2004 at http://www.batcon.org/discover/ffecon3.html.

Ayensu, E. 1974. Plant and Bat Interactions in West Africa. Annals of the Missouri Botanical Garden, 61/3: 702-727.

Fenton, M., L. Crerar. 1984. Cervical Vertebrae in Relation to Roosting Posture in Bats. Journal of Mammology, 65: 395-403.

Jones, C. 1972. Comparative Ecology of Three Pteropid Bats in Rio Muni, West Africa. Journal of Zoology, London, 167: 353-370.

Jones, C. 1971. The Bats of Rio Muni, West Africa. Journal of Mammology, 52: 121-140.

Marshall, A., A. McWiliam. 1982. Ecological Observations on Epomorphorine Fruit-Bats (Megachiroptera) in West African Savanna Woodland. Journal of Zoology, London, 198: 53-67.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore: The Johns Hopkins University Press.

Owen-Ashley, N., D. Wilson. 1998. Micropteropus pusillus. Mammalian Species, 577: 1-5.

Thomas, D., A. Marshall. 1984. Reproduction and Growth in Three Species of West African Fruit Bats. Journal of Zoology, London, 202: 265-281.

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