Overview

Distribution

Range Description

This bat is broadly distributed across the lowland rainforest and savanna zones of Africa from Senegal in the west, through to South Africa in the south and Ethiopia in the east (possibly ranging into Djibouti and southern Eritrea). It is also present on the extreme southwest Arabian Peninsula, where it has been recorded from Yemen and Saudi Arabia (Harrison and Bates 1991). Populations of this bat occur on several offshore islands including the Gulf of Guinea islands and Zanzibar, Pemba and Mafia (off Tanzania) (Bergmans 1990; Simmons 2005). There is a possibly disjunct population in the Air Mountains of Niger. Distribution at northern and southern extremes of the range is patchy and erratic. It is also sparse or absent in large areas of the Horn of Africa, central East Africa, and elsewhere (Bergmans, 1990). This bat is a migratory species in parts of its range; populations migrate from the West African forest north into the savanna zone during the major wet season. It ranges from sea level to around 2,000 m asl (Ruwenzori Mountains).
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Physical Description

Morphology

Physical Description

E. helvum is not entirely straw-colored as its common name would suggest. The neck and back display this signature color while the ventral side of the body is a duller color of brown or grey.

This is one of the larger species of fruit bats. The males are slightly larger than the females. The head and body length is reported to be between 143 and 215 mm. Weights range between 230 and 350 g.

The wings are large and narrow, allowing the bat to fly long distances and not expend as much energy trying to flap them a lot. The wingspan can reach as much as 762 mm.

The head is large and pointed with large eyes and no white facial markings. (Happold, 1987)

Range mass: 230 to 350 g.

Range length: 143 to 215 mm.

Range wingspan: 762 (high) mm.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This adaptable species has been recorded from a very wide range of habitats. It is commonly found in moist and dry tropical rain forest, including evergreen forest habitats in the form of coastal (including mangrove) and riverine forest, through moist and dry savanna and mosaics of these and similar habitat types. Populations can persist in modified habitats and the species is often recorded in urban areas, such as wooded city parks.

Systems
  • Terrestrial
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These bats occupy a wide range of habitats, from coastal forests to dry, arid regions are used during the year. Prime habitat is tropical forests because of the abundance of food. Straw-colored fruit bats are found at elevations from sea level to 2000 m. These animals typically roost in tall trees, but have also been found in caves. There is great interaction with human communities as well.

Range elevation: sea level to 2000 m.

Habitat Regions: temperate ; tropical ; terrestrial

Terrestrial Biomes: savanna or grassland ; forest ; rainforest

Other Habitat Features: urban ; suburban ; agricultural

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Trophic Strategy

Food Habits

E. helvum is frugivorous. Food is can be consumed while hanging by the phalanges of the feet. The food is eaten noisily. The juices are ingested and the fibrous material is discarded. In addition to consuming fruit juices, these animals are reported to chew up wood and bark, apparently to obtain moisture.

Foods eaten include: Borassus spp., dates, baobab flowers, Adansonia digitata, Bombax spp., Erythrina spp., mangoes, pawpaws, avocado pears, figs, passion fruit, custard apples and loquats.

Plant Foods: wood, bark, or stems; fruit

Primary Diet: herbivore (Folivore , Frugivore )

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Associations

Ecosystem Roles

Because these bats visit flowers, they play a role in pollination. They also serve as agents in seed dispersal.

Ecosystem Impact: disperses seeds; pollinates

  • Mutere, F. 1980. Eidolon Helvum Revisited. Pp. 145-150 in D Wilson, A Gardner, eds. Proceedings Fifth International Bat Research Conference. Lubbock, Texas, U.S.A.: Texas Tech Press.
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Predation

Little information is available on species which prey upon these bats. Suspected predators include owls, eagles, snakes, buzzards, and civets. Humans are know to consume E. helvum in Zaire and West Africa.

Known Predators:

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Known predators

Eidolon helvum is prey of:
Strigiformes
Serpentes
Accipitridae
Buteo
Homo sapiens
Viverridae

This list may not be complete but is based on published studies.
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Life History and Behavior

Behavior

Communication and Perception

Little information on communication in this species could be found. However, these animals are reported to be quite noisy. In addition to being loud eaters, they apparently chatter to one another in their roosts, indicating that some form of acoustic commmunication is employed. Because they roost in such large groups, it is likely that individuals come into physical contact frequently, and so probably use some sort of tactile communication as well.

Communication Channels: tactile ; acoustic

Perception Channels: visual ; acoustic

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Life Cycle

Development

The young are the result of delayed implantation. The embryonic development is 4 months before partrution with a birth weight of 45-50 grams. (Nowak, 1997)

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Life Expectancy

Lifespan/Longevity

Fifteen years is the expected life span of E. helvum. Some individuals do make it to their early twenties, and one individual is reported to have reached 21 years and ten months of age.

Range lifespan

Status: captivity:
22 (high) years.

Average lifespan

Status: wild:
15 years.

Average lifespan

Status: captivity:
21.8 years.

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Lifespan, longevity, and ageing

Maximum longevity: 21.8 years (captivity) Observations: Although the gestation period takes at least 9 months, the embryonic development is completed in 4 months (Ronald Nowak 1999).
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Reproduction

Information on the mating system of these animals is lacking.

Mating occurs in colonies from April to June. The reproductive cycle responds to rainfall, and allows weaning of young to proceed at the time of greatest food availability.

Pairs breed when the dry season begins. There is a delay in the implantation of the embryo in most, but not all, populations. The gestation period typically lasts 9 months, but the embryo only takes 4 months to develop. In populations without delayed implantation, births occur just 4 months after mating.

The young are born in February and March. Females give birth to a single offspring that weighs 50 grams at birth.

Breeding interval: These animals breed annually.

Breeding season: These bats breed from April to June

Range number of offspring: 1 to 2.

Average number of offspring: 1.

Average gestation period: 9 months.

Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization (Internal ); viviparous ; delayed implantation

Average birth mass: 50 g.

Average gestation period: 275 days.

Average number of offspring: 1.

The straw-colored fruit bat has female parental care, like all other mammals. The female nurses her offspring until it is ready to forage on its own. In this species, young are not able to fly at birth,and so are considered altricial. Although females give birth to their young in large colonies, there are no reports of cooperative care of young, nor of paternal involvement in care of offspring.

Parental Investment: altricial ; pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female)

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Molecular Biology and Genetics

Molecular Biology

Statistics of barcoding coverage: Eidolon helvum

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Specimens with Barcodes: 22
Species With Barcodes: 1
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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
NT
Near Threatened

Red List Criteria

Version
3.1

Year Assessed
2008

Assessor/s
Mickleburgh, S., Hutson, A.M., Bergmans, W., Fahr, J. & Racey, P.A.

Reviewer/s
Hutson, A.M., Racey, P.A. (Chiroptera Red List Authority) & Cox, N. (Global Mammal Assessment Team)

Contributor/s

Justification
Listed as Near Threatened because this species is in significant decline (but at a rate of less than 30% over three generations (approximately fifteen years)) because it is being seriously over-harvested for food and medicine, making the species close to qualifying for Vulnerable. Under criterion A2d.

History
  • 2004
    Least Concern
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This is a very abundant and common species that has no legal protection.

US Migratory Bird Act: no special status

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: near threatened

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Population

Population
In general this is a common species forming large colonies of thousands to even millions of individuals. Within colonies they form tight clusters of up to 100 animals, although in particularly large colonies this clustering may not be so obvious. Colonies may show extreme roost-site fidelity. During migration this species disperses into small groups. There is evidence of a widespread decline (P. Racey pers. comm.). A well-known colony in Kampala (Uganda) declined in numbers over a forty-year period from ca. 250,000 animals to 40,000 in 2007 (Monadjem et al. 2007). Eidolon helvum is the most heavily harvested bat for bushmeat in West and Central Africa, and this is believed to be a major factor in reportied population declines (P. Racey pers. comm.).

Population Trend
Decreasing
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Threats

Major Threats
In general there are no major threats to this widespread and adaptable species. It is, however, locally threatened in parts of its range by severe deforestation, and more generally across West and Central Africa by hunting for food and medicinal use. It is the most heavily harvested bat for bushmeat in West and Central Africa, and one of the most frequently consumed mammals in this region (P. Racey pers. comm.). Large pre-migration colonies are considered particularly vulnerable to any threats. In some areas it is considered to be a pest species and roosting locations may be restricted by cutting down trees. Trees are also cut down in order to catch bats for the market (P. Racey pers. comm.).
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Management

Conservation Actions

Conservation Actions
This species is present in a few protected areas across its range, with a large roosting colony in Kasanka National Park, Zambia. There is a need to identify and protect important roosting sites, and a better understanding of the migratory patterns of this species would be beneficial to any conservation activities. The highest priority is to limit the harvesting of this species to sustainable levels.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

Agriculture is greatly affected by E. helvum because these bats live in large colonies that roost near their food source. They can feed heavily in plantations. It is difficult to assess the relative utility of the species as a polinator, versus its negative impact as a crop pest.

Negative Impacts: crop pest

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Economic Importance for Humans: Positive

E. helvum are an important diet item for humans in some areas. Straw-colored fruit bats are also important pollinating agents for economically important trees in families Moracea and Bombacear.

Positive Impacts: food ; pollinates crops

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Wikipedia

Straw-coloured fruit bat

The straw-coloured fruit bat (Eidolon helvum) is a large fruit bat that is the most widely distributed of all the African megabats. It is quite common throughout its area ranging from the southwestern Arabian Peninsula, across forest and savanna zones of sub-Saharan Africa and Madagascar. They have recently been classified as Near Threatened on the IUCN Red List due to a decreasing population trend. Straw-coloured fruit bats travel in massive colonies of at least 100,000 bats and sometimes massing up to 1 million. Their necks and backs are a yellowish-brown colour, while their undersides are tawny olive or brownish.

Appearance[edit]

The straw-coloured fruit bat got its name from the silky yellowish or straw colour of its exterior. The wings are black, and the back hair is pale and tawny. Males are generally bright orange and females are usually yellowish. The bats have large cheeks, eyes, and ears. The average weight of these bats ranges from 8 to 12 oz (230 to 340 g) and the animals grow to 5.7 to 9 in (14 to 23 cm) in length, with wings spanning up to 30 in (76 cm). Males are generally larger than females. The bat's heart is very large, and its wings are long and tapered at the tip. The cheeks of the bat are also large and pouch-like.[1]

Lifestyle[edit]

The straw-coloured fruit bat is a highly social species. The bats tend to live in groups of over 100,000 and at times that number may increase to almost one million. At night the bats leave the roost in smaller groups to find food by sight and smell. They have also been seen chewing on soft wood for moisture. These bats can also pollinate flowers and disperse seeds through the forests. They are the main agents of seed dispersal for the increasingly rare and economically significant African teak tree Milicia excelsa.[2]

Although they feed at night, straw-coloured fruit bats are not necessarily nocturnal. During the day, they will be found resting and moving among the colony. Year to year, season to season, the bats will return to the same place where they found food the previous year or season.

Diet[edit]

The diets of straw-coloured fruit bats vary depending on whether or not they are living in captivity. Wild bats usually eat bark, flowers, leaves, nectar, and fruits. In captivity, they are fed various mixes, including apples, oranges, bananas, grapes, and cantaloupe. In some zoos, they are also fed a marmoset diet.[3]

Distribution[edit]

Eidolon helvum is the most widely distributed fruit bat in Africa, and perhaps the world. It appears mainly in Africa, mostly among the sub-Saharan climates, in many forest and savanna zones, around the southwestern Arabian peninsula, and in Madagascar. It can also be found in urban areas and at altitudes up to 2,000 m (6,600 ft). It prefers tall trees for roosting.

Notes[edit]

  1. ^ Arkon Zoo Information on Straw Colored Bats
  2. ^ Taylor, D. A. R. et al. The role of the fruit bat, Eidolon helvum, in seed dispersal, survival, and germination in Milicia excelsa, a threatened West African hardwood. Northern Arizona University School of Forestry.
  3. ^ Oregon Zoo Information on Straw Colored Bats

References[edit]

Mickleburgh, S., Hutson, A.M., Bergmans, W., Fahr, J. & Racey, P.A. 2008. Eidolon helvum. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. www.iucnredlist.org.

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