Overview

Brief Summary

Hammer-headed bat (Hypsignathus monstrosus)

This species is widespread in West and Central Africa. It ranges from Guinea-Bissau in the west, to northwestern Angola in the south, and as far east as western Ethiopia and western Kenya (near Lake Victoria). It has been recorded to at least 1,800 m asl.



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Geographic Range

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Hypsignathus monstrosus is found in the forested regions of central Africa. It has been recorded from Senegal to northern Angola (Langevin and Barclay, 1990; Koopman, 1975).

Biogeographic Regions: ethiopian (Native )



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Physical Description

Morphology

Physical Description

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H. monstrosus is the largest bat found in Africa, with males being significantly larger than females. Males range in mass from 228 g to 450 g, averaging 377 g. Females are about half the size, weighing from 218 to 377 g, and averaging 275 g. Males range in length from 220 to 280 mm, with an average of 250 mm. Females measure 195 to 225 mm, averaging 210 mm. Males have a wingspan of 686 to 970 mm, and females have an average wingspan of 840 mm.

The species is sexually dimorphic in facial features as well as in size. Males have an enlarged rostrum and larynx, and a large, square head. They can also be distinguished by their huge, pendulous lips, flaps around a warty snout, a bald, split chin and cheek pouches. To human eyes, these bats are really ugly, prehaps accounting for their species name, "monstrosus." Females also have a square-shaped head, but their muzzle is fox-shaped and lacks the unique lip, snout, and chin characteristics of the male.

The ears are rounded at the base and the tail is very short. There is a claw on the second finger and this bat has large, flexible thumbs.

The pelage is slate-brown and there is a white collar of fur that stretches from shoulder to shoulder. The face and wing membranes are dark brown and the ears are dark brown with white tufts at the base.

(Langevin and Barclay, 1990; Kulzer, 1990; Macnamara et al., 1979)

Range mass: 218-228 to 377-450 g.

Average mass: 275-377 g.

Range length: 195-220 to 225-280 mm.

Average length: 210-250 mm.

Range wingspan: 686 (males) to 970 (males) mm.

Average wingspan: 840 (females) mm.

Sexual Dimorphism: male larger



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Ecology

Habitat

Habitat and Ecology

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Habitat and Ecology

This species is found in a wide range of habitats, including lowland tropical moist forest, riverine forest, swamp forest, mangroves, palm forest, and less commonly in moist savanna. This bat has a lek mating system at many locations, but not at all known sites (e.g.. at Tai National Park, Côte d'Ivoire). The males gather into groups (leks) of a few hundred animals and attempt to attract females. The species roosts 20 to 30 metres up in the forest canopy (Bradbury 1977), usually on exposed branches beneath a cover of dense vegetation. It feeds The diet is primarily figs and other fruit, including cultivated crops.

Systems

•Terrestrial



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Hammerhead bats are found at elevations less than 1800 m. They prefer riverine forests, swamps, mangroves, and palm forests. (MacNamara et al., 1979; Langevin and Barclay, 1990)

Range elevation: 1800 (high) m.

Habitat Regions: tropical

Terrestrial Biomes: forest

Wetlands: swamp

Other Habitat Features: riparian



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Trophic Strategy

Food Habits

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Figs make up most of the H. monstrosus diet, but this bat may also include the juice and soft pulp of mangos, bananas and guavas. Van Deusan (1968) reports H. monstrosus showing some carnivorous behavior by attacking chickens to drink their blood and scavenging for meat.

Males and females use different foraging strategies. The females rely on established, dependable food resources of moderate quality. The males prefer to search out high quality food patches, flying up to 10 km to find the best food (Bradbury ,1981). This difference may reflect different metabolic needs, based on the difference in size between males and females.

Animal Foods: blood; carrion

Plant Foods: fruit

Primary Diet: herbivore (Frugivore )



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Associations

Ecosystem Roles

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Although hammerhead bats are frugivorous, they consume mainly the juice and occasionally the pulp of their meal. Because of this, they are not very good seed distributors. However, given their size, they make a pretty good meal for a bird of prey and may affect prey populations, dependingupon their availability (Langevin and Barclay, 1900).



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Predation

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To avoid predation, the hammerhead bat roosts high in forest canopy (20-30m), in groups of up to 25 individuals. During the day, they are inactive and rely on camouflage to hide them from predators (Kulzer, 1990).

Although humans and birds of prey may take some of these bats, parasites seem to be the main threat to their health. These have their own specific hepatoparasite, Hepatocystis carpenteri (Langevin and Barclay, 1990).

Known Predators:

•humans (Homo sapiens)

•birds of prey (Falconiformes and Strigiformes)





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Known predators

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Hypsignathus monstrosus is prey of:

Strigiformes

Homo sapiens

This list may not be complete but is based on published studies.

•Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2006. The Animal Diversity Web (online). Accessed February 16, 2011 at http://animaldiversity.org. http://www.animaldiversity.org



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Life History and Behavior

Life Expectancy

Lifespan/Longevity

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The hammerhead bat has a life expectancy of up to 30 years (Kulzer, 1990).

Average lifespan

Status: wild: 30 years.



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Lifespan, longevity, and ageing

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Observations: Not much is known about the longevity of this species. One specimen was about 12 years old when it died in captivity (Richard Weigl 2005). Maximum longevity could be underestimated, though, and it has been estimated that these animals live up to 30 years (Bernhard Grzimek 1990).



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Reproduction

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H. monstrosus has a lek or arena mating system. The bats gather at night along a stream or river bed where males line up on tree branches in a long, narrow strip. They space themselves evenly in 10 m intervals and advertise themselves to females. An assemblage could contain from 25 to 132 bats.

Males attract females with loud vocalizations, including guttoral honking and croaking. They also use wing flapping. The bizzare head shape of the males of this species probably aids them in making favorable vocalization. Females fly through the arena to assess the males, then choose a mate and sit beside him on the branch.

Males emit a high buzz call when chosen and copulation begins. The duration of copulation is only 30-60 seconds and the pair leave independent of each other to forage. There are two mating sessions per night, one around 9:00 PM and the next at 4:00 AM. The early evening session is when most copulations occur and the later session is mainly for male agonistic behavior as they establish what territory in the strip will be theirs to display (Langevin and Barclay, 1990).

The species is highly polygynous. Nowak (1999) reports that only 6 percent of the males in a population accounted for 79 percent of matings. The successful males tended to be clumped together in the assemlage of males, indicating the importance of territory within the strip.

Mating System: polygynous

Data on when hammerhead bats breed vary. Some studies suggest that the peak of births occurs August to September during the middle of the rainy season and then another at the end of the rainy season, from October to December (Wolton et al., 1982). Others suggest the breeding peaks are at six month intervals and that are synchronized with the two dry seasons (Bradbury, 1977). In captivity, females maintain the same cycle they exhibit in the wild, breeding during June to August, and again in December to January (Nowak, 1999).

Females typically produce one offspring at a time, although twins have been seen. Newborn hammerhead bats weigh about 40 g (Nowak, 1999). Gestation length has not been reported for this species, nor has time until weaning. other Pteropodids vary greatly in these parameters, so it is difficult to speculate on this species based trends within the family.

The male H. monstrosus reaches sexual maturity at approximately 18 months and does not develop sexually dimorphic facial features until 12 months. Females are sexually mature at 6 months and full size at 12 months (Bradbury, 1977).

Breeding season: Breeding probably occurs in late summer and early in winter.

Range number of offspring: 1 to 2.

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

Average birth mass: 40 g.

Average number of offspring: 1.3.

Average age at sexual or reproductive maturity (male)

Sex: male: 420 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 180 days.

Parental care has not been reported for this species, but is likely to be the responsibility solely of females. Females provide milk, protection, grooming, and other essentials to the young in highly polygynous species. In some species, females carry their young with them while they fly around, and in others females park their young in roosts while they forage. There are no reports regarding what H. monstrosus does with its young.

Parental Investment: female parental care



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Conservation

Conservation Status

IUCN Red List Assessment

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Red List Category

LC

Least Concern

Red List Criteria

Version

3.1

Year Assessed

2008

Assessor/s

Mickleburgh, S., Hutson, A.M., Bergmans, W. & Fahr, J.

Reviewer/s

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

Justification

Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

History

•2004

Least Concern

•1996

Lower Risk/least concern

(Baillie and Groombridge 1996)



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This species has no special conservation status.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern



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Trends

Population

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Population

It is a locally common species. Roosts can contain as many as 25 bats, but the average roost size is fewer than five animals.

Population Trend

Unknown



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Threats

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Major Threats

This species is locally threatened by habitat destruction, particularly the loss of riverine forests. In parts of its range it is hunted for subsistence food.



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Management

Conservation Actions

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Conservation Actions

There appear to be no direct conservation measures in place. It has been recorded from Tai National Park (Côte d'Ivoire) and in view of its wide range, is presumably present in some other protected areas. Further studies are needed into the distribution of this species.



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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

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This species has been reported to kill chickens (see Food Habits, above).

Negative Impacts: crop pest



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Economic Importance for Humans: Positive

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There have been no reports of the affect of this bat on humans. However, humans do hunt these animals, as noted under Predation, above, so they do provide food.

Positive Impacts: food



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Wikipedia

Hammer-headed bat

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The Hammer-headed Bat (Hypsignathus monstrosus), also known as the Big-lipped Bat, is a megabat widely distributed in equatorial Africa. This large bat is found in riverine forests, mangroves, swamps, and palm forests at elevations less than 1800 meters.

Contents

•1 Taxonomy

•2 Physical description

•3 Ecology and behavior

•4 Reproduction and mortality

•5 Interactions with humans

•6 Footnotes

•7 External links

Taxonomy[edit source | edit]

The hammer-headed bat is a member of the family Pteropodidae. Pteropodidae is divided into two subfamilies, Macroglossinae which contains six genera, and Pteropodinae containing thirty-six genera including Hypsignathus. The family Pteropodidae is found within the suborder, Megachiroptera. This group is commonly referred to as the megabats or flying foxes.

Physical description[edit source | edit]

The hammer-headed bat is the largest bat in Africa with a wingspan of 686 to 970 mm (27.0 to 38 in) and a total length of 195 to 285 mm (7.7 to 11.2 in). Males, ranging from 228 to 450 g (8.0 to 16 oz), are significantly larger than females, which range from 218 to 377 g (7.7 to 13.3 oz).[2][3]

Pelage is grey-brown to slaty-brown with a whitish collar of fur extending from shoulder to shoulder.[4] The flight membranes are brown and the ears are dark brown with a tuft of white fur at the base. The face is dark brown with a few long, stiff whiskers around the mouth.

The skull may be diagnosed by specific dental features. The second premolar and molars are markedly lobed. This feature is specific for this genus, and no other African fruit bats have this characteristic.

There is extreme sexual dimorphism in this species.[5] The male possesses an enormous head for producing loud honking calls.[5] The enlarged rostrum, larynx and lips allow these sounds to be extremely resonant. The larynx is one half the length of the vertebral column and fills out most of the thoracic cavity. It is nearly three times larger in males than females. The male also has a hairless split chin and warty rostrum with wrinkled skin around it. Females have a much more fox-like appearance similar to most fruit bats.[4]

Ecology and behavior[edit source | edit]

Hammer-headed bats are frugivores. Figs make up much of their diet, but they may also include mangos, bananas and guavas. There are some complications inherent in a fruit diet such as insufficient protein intake. It is suggested that fruit bats compensate for this by possessing a proportionally longer intestine compared to insectivorous species.[4] This enhances their ability to absorb protein. They also have very rapid digestive systems allowing these bats to assimilate high amounts of fruit to ensure that adequate protein is absorbed. It is also suggested that by eating a wide variety of fruits with varying protein contents, fruit bats are able to maintain an entirely frugivorous diet.[6]

Generally fruit is picked and taken to a nearby tree where it is chewed, the juice squeezed out and the pulp discarded. Since they often do not consume the pulp, these bats are not considered to be good seed distributors.[7] Males may forage long distances (up to 10 km) to locate the highest quality food. Females rely on established feeding routes that offer a constant supply of lower quality food. This may reflect different metabolic requirements based on body size differences.

Large bats often experience difficulties with overheating during flight. The limited thermoregulatory capabilities of flying bats appears to be one factor closely associated with why flight activity primarily occurs during cooler nocturnal temperatures. It has been found that hammer-headed bats are able to tolerate higher ambient temperatures during flight than other bats.[8] This ability is associated with this bat’s high thermal conductance (Cf) which is defined as the total heat loss less the heat loss due to evaporation divided by body temperature less the ambient temperature (Cf = [H1 – He]/[Tb – Ta]). However, they are especially sensitive to ambient temperatures below 11°C and a decrease in flight coordination is seen. Due to the large surface area of the wing, convective heat loss to cool air may be significant enough to chill flight muscles preventing the precise coordination essential for flight.

These bats are nocturnal, roosting during the day in the forest canopy. They rely on camouflage to hide them from predators.[4] Specific species of trees are not selected for roosting, however some roosts may be used for long periods of time. Roosts are generally 20–30 meters from the ground.

The main predators of this species are humans and nocturnal and diurnal birds of prey. However, infection by parasites is often the most significant problem for the hammer-headed bat. Adults are often infected with mites and the hepatoparasite, Hepatocystis carpenteri.

Reproduction and mortality[edit source | edit]

Little is known about reproduction in hammer-headed bats. In some populations breeding is thought to take place semi-annually during the dry seasons. The timing of the dry season varies depending on the locality, but in general there are two breeding seasons, one from June to August and the other from December to February.[4] However, in other populations, breeding is not restricted to dry seasons and occurs during all months of the year.

This species is often cited as a classic model of lek mating.[9] In this type of mating system, males cluster in dense groups at specific locations known as mating arenas.[9] In some populations of hammer-headed bats, males gather along rivers at night and display by rapid wing flapping accompanied by loud vocalizations.[10] An arena may contain from 25 to 132 males. Females fly through the arena assessing the males. Once the female’s choice is made, the female lands on the branch and sits beside the male. Once chosen, the male emits a buzzing call and copulation ensues.

However, some populations of hammer-headed bats do not use the lek mating strategy. Males actively display but are not found clustering in groups.[11] This species is highly polygamous. Some estimates suggest that as few as six percent of the males in a population account for up to seventy-nine percent of the matings.

Females generally produce one offspring at a time. Neither gestation nor time until weaning have been reported for this species. Females mature more quickly than males and are sexually mature after six months. They continue to grow and reach adult size at nine months. Males do not reach sexual maturity until approximately eighteen months of age and they do not obtain their unique facial morphology until twelve months. Compared with other bats, this bat is rather long-lived with an average life expectancy of thirty years in the wild.

Interactions with humans[edit source | edit]

H. monstrosus has no special conservation status. In 2004, the IUCN Red List of Threatened Species listed this species as LC (least concern) on the basis of its widespread distribution and lack of threats to its habitat.[1]

Due to this bat’s diet of fruit, it may be considered a crop pest. It has also been observed to attack live chickens.[12] This observation was reported once and cannot be considered a regular occurrence. Humans hunt this large bat and consume it as bushmeat.

The hammer-headed bat is one of three species of African fruit bat claimed to be asymptomatically infected with the Ebola virus.[13] It is not known whether these species are incidental hosts or a reservoir of Ebolavirus infection for humans and other terrestrial mammals.

Footnotes[edit source | edit]

1.^ a b S. Mickleburgh, A. M. Hutson, W. Bergmans & J. Fahr (2008). "Hypsignathus monstrosus". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. Retrieved February 2, 2010.

2.^ Nowak M., R. (1994). Walker's Bats of the World. Johns Hopkins University Press. pp.63-64/

3.^ [1]

4.^ a b c d e Langevin, P., R. Barclay. 1990. "Hypsignathus monstrosus". Mammalian Species, 357: 1-4.

5.^ a b Altringham D., J. (1996). "Bats: Biology and Behaviour." Oxford University Press.

6.^ Courts S E. (1998) "Dietary strategies of Old World fruit bats (Megachiroptera, Pteropodidae): how do they obtain sufficient protein?" Mammal Rev. 28(4):185-194.

7.^ Eisenberg J F and Wilson D E. (1978) "Relative brain size and feeding strategies in the Chiroptera". Evolution, 32(4):740-751.

8.^ Carpenter R E. (1986) "Flight physiology of intermediate-sized fruit bats (Pteropodidae)". J Exp Biol. 120:79-103.

9.^ a b Bradbury W., J. (1977) "Lek Mating Behavior in the Hammer-headed Bat", Zeitschrift für Tierpsychologie, 45(3):225-255.

10.^ Griffin R., D. (1986). "Communication in the Chiroptera." JSTOR 61(2): 284.

11.^ Truxton G T. 2001. "The calling behavior and mating system of a non-lekking population of Hypsignathus monstrosus". Ph.D. dissertation. State University of New York at Stony Brook. 240 pages.

12.^ Deusen M. van, H. (1968). "Carnivorous Habits of Hypsignathus monstrosus " JSTOR 49(2): 335-336.

13.^ Brahic, C. (Nov. 30, 2005). "Fruit bats blamed for Ebola outbreaks."

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Distribution

Range Description

This species is widespread in West and Central Africa. It ranges from Guinea-Bissau in the west, to northwestern Angola in the south, and as far east as western Ethiopia and western Kenya (near Lake Victoria). It has been recorded to at least 1,800 m asl.
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Geographic Range

Hypsignathus monstrosus is found in the forested regions of central Africa. It has been recorded from Senegal to northern Angola (Langevin and Barclay, 1990; Koopman, 1975).

Biogeographic Regions: ethiopian (Native )

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Physical Description

Morphology

Physical Description

H. monstrosus is the largest bat found in Africa, with males being significantly larger than females. Males range in mass from 228 g to 450 g, averaging 377 g. Females are about half the size, weighing from 218 to 377 g, and averaging 275 g. Males range in length from 220 to 280 mm, with an average of 250 mm. Females measure 195 to 225 mm, averaging 210 mm. Males have a wingspan of 686 to 970 mm, and females have an average wingspan of 840 mm.

The species is sexually dimorphic in facial features as well as in size. Males have an enlarged rostrum and larynx, and a large, square head. They can also be distinguished by their huge, pendulous lips, flaps around a warty snout, a bald, split chin and cheek pouches. To human eyes, these bats are really ugly, prehaps accounting for their species name, "monstrosus." Females also have a square-shaped head, but their muzzle is fox-shaped and lacks the unique lip, snout, and chin characteristics of the male.

The ears are rounded at the base and the tail is very short. There is a claw on the second finger and this bat has large, flexible thumbs.

The pelage is slate-brown and there is a white collar of fur that stretches from shoulder to shoulder. The face and wing membranes are dark brown and the ears are dark brown with white tufts at the base.

(Langevin and Barclay, 1990; Kulzer, 1990; Macnamara et al., 1979)

Range mass: 218-228 to 377-450 g.

Average mass: 275-377 g.

Range length: 195-220 to 225-280 mm.

Average length: 210-250 mm.

Range wingspan: 686 (males) to 970 (males) mm.

Average wingspan: 840 (females) mm.

Sexual Dimorphism: male larger

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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
This species is found in a wide range of habitats, including lowland tropical moist forest, riverine forest, swamp forest, mangroves, palm forest, and less commonly in moist savanna. This bat has a lek mating system at many locations, but not at all known sites (e.g.. at Tai National Park, Côte d'Ivoire). The males gather into groups (leks) of a few hundred animals and attempt to attract females. The species roosts 20 to 30 metres up in the forest canopy (Bradbury 1977), usually on exposed branches beneath a cover of dense vegetation. It feeds The diet is primarily figs and other fruit, including cultivated crops.

Systems
  • Terrestrial
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Hammerhead bats are found at elevations less than 1800 m. They prefer riverine forests, swamps, mangroves, and palm forests. (MacNamara et al., 1979; Langevin and Barclay, 1990)

Range elevation: 1800 (high) m.

Habitat Regions: tropical

Terrestrial Biomes: forest

Wetlands: swamp

Other Habitat Features: riparian

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Trophic Strategy

Food Habits

Figs make up most of the H. monstrosus diet, but this bat may also include the juice and soft pulp of mangos, bananas and guavas. Van Deusan (1968) reports H. monstrosus showing some carnivorous behavior by attacking chickens to drink their blood and scavenging for meat.

Males and females use different foraging strategies. The females rely on established, dependable food resources of moderate quality. The males prefer to search out high quality food patches, flying up to 10 km to find the best food (Bradbury ,1981). This difference may reflect different metabolic needs, based on the difference in size between males and females.

Animal Foods: blood; carrion

Plant Foods: fruit

Primary Diet: herbivore (Frugivore )

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Associations

Ecosystem Roles

Although hammerhead bats are frugivorous, they consume mainly the juice and occasionally the pulp of their meal. Because of this, they are not very good seed distributors. However, given their size, they make a pretty good meal for a bird of prey and may affect prey populations, dependingupon their availability (Langevin and Barclay, 1900).

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Predation

To avoid predation, the hammerhead bat roosts high in forest canopy (20-30m), in groups of up to 25 individuals. During the day, they are inactive and rely on camouflage to hide them from predators (Kulzer, 1990).

Although humans and birds of prey may take some of these bats, parasites seem to be the main threat to their health. These have their own specific hepatoparasite, Hepatocystis carpenteri (Langevin and Barclay, 1990).

Known Predators:

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Known predators

Hypsignathus monstrosus is prey of:
Strigiformes
Homo sapiens

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

Life Expectancy

Lifespan/Longevity

The hammerhead bat has a life expectancy of up to 30 years (Kulzer, 1990).

Average lifespan

Status: wild:
30 years.

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Lifespan, longevity, and ageing

Observations: Not much is known about the longevity of this species. One specimen was about 12 years old when it died in captivity (Richard Weigl 2005). Maximum longevity could be underestimated, though, and it has been estimated that these animals live up to 30 years (Bernhard Grzimek 1990).
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Reproduction

H. monstrosus has a lek or arena mating system. The bats gather at night along a stream or river bed where males line up on tree branches in a long, narrow strip. They space themselves evenly in 10 m intervals and advertise themselves to females. An assemblage could contain from 25 to 132 bats.

Males attract females with loud vocalizations, including guttoral honking and croaking. They also use wing flapping. The bizzare head shape of the males of this species probably aids them in making favorable vocalization. Females fly through the arena to assess the males, then choose a mate and sit beside him on the branch.

Males emit a high buzz call when chosen and copulation begins. The duration of copulation is only 30-60 seconds and the pair leave independent of each other to forage. There are two mating sessions per night, one around 9:00 PM and the next at 4:00 AM. The early evening session is when most copulations occur and the later session is mainly for male agonistic behavior as they establish what territory in the strip will be theirs to display (Langevin and Barclay, 1990).

The species is highly polygynous. Nowak (1999) reports that only 6 percent of the males in a population accounted for 79 percent of matings. The successful males tended to be clumped together in the assemlage of males, indicating the importance of territory within the strip.

Mating System: polygynous

Data on when hammerhead bats breed vary. Some studies suggest that the peak of births occurs August to September during the middle of the rainy season and then another at the end of the rainy season, from October to December (Wolton et al., 1982). Others suggest the breeding peaks are at six month intervals and that are synchronized with the two dry seasons (Bradbury, 1977). In captivity, females maintain the same cycle they exhibit in the wild, breeding during June to August, and again in December to January (Nowak, 1999).

Females typically produce one offspring at a time, although twins have been seen. Newborn hammerhead bats weigh about 40 g (Nowak, 1999). Gestation length has not been reported for this species, nor has time until weaning. other Pteropodids vary greatly in these parameters, so it is difficult to speculate on this species based trends within the family.

The male H. monstrosus reaches sexual maturity at approximately 18 months and does not develop sexually dimorphic facial features until 12 months. Females are sexually mature at 6 months and full size at 12 months (Bradbury, 1977).

Breeding season: Breeding probably occurs in late summer and early in winter.

Range number of offspring: 1 to 2.

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

Average birth mass: 40 g.

Average number of offspring: 1.3.

Average age at sexual or reproductive maturity (male)

Sex: male:
420 days.

Average age at sexual or reproductive maturity (female)

Sex: female:
180 days.

Parental care has not been reported for this species, but is likely to be the responsibility solely of females. Females provide milk, protection, grooming, and other essentials to the young in highly polygynous species. In some species, females carry their young with them while they fly around, and in others females park their young in roosts while they forage. There are no reports regarding what H. monstrosus does with its young.

Parental Investment: female parental care

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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
LC
Least Concern

Red List Criteria

Version
3.1

Year Assessed
2008

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

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

Contributor/s

Justification
Listed as Least Concern in view of its wide distribution, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a more threatened category.

History
  • 2004
    Least Concern
  • 1996
    Lower Risk/least concern
    (Baillie and Groombridge 1996)
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This species has no special conservation status.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

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Population

Population
It is a locally common species. Roosts can contain as many as 25 bats, but the average roost size is fewer than five animals.

Population Trend
Unknown
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Threats

Major Threats
This species is locally threatened by habitat destruction, particularly the loss of riverine forests. In parts of its range it is hunted for subsistence food.
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Management

Conservation Actions

Conservation Actions
There appear to be no direct conservation measures in place. It has been recorded from Tai National Park (Côte d'Ivoire) and in view of its wide range, is presumably present in some other protected areas. Further studies are needed into the distribution of this species.
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Relevance to Humans and Ecosystems

Benefits

Economic Importance for Humans: Negative

This species has been reported to kill chickens (see Food Habits, above).

Negative Impacts: crop pest

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Economic Importance for Humans: Positive

There have been no reports of the affect of this bat on humans. However, humans do hunt these animals, as noted under Predation, above, so they do provide food.

Positive Impacts: food

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Wikipedia

Hammer-headed bat

The hammer-headed bat (Hypsignathus monstrosus), also known as the big-lipped bat, is a megabat widely distributed in equatorial Africa. This large bat is found in riverine forests, mangroves, swamps, and palm forests at elevations less than 1800 meters.

Taxonomy[edit]

The hammer-headed bat is a member of the family Pteropodidae. Pteropodidae is divided into two subfamilies, Macroglossinae which contains six genera, and Pteropodinae containing thirty-six genera including Hypsignathus. The family Pteropodidae is found within the suborder, Megachiroptera. This group is commonly referred to as the megabats or flying foxes.

Physical description[edit]

The hammer-headed bat is the largest bat in Africa with a wingspan of 686 to 970 mm (27.0 to 38.2 in) and a total length of 195 to 285 mm (7.7 to 11.2 in). Males, ranging from 228 to 450 g (8.0 to 15.9 oz), are significantly larger than females, which range from 218 to 377 g (7.7 to 13.3 oz).[2][3]

Pelage is grey-brown to slaty-brown with a whitish collar of fur extending from shoulder to shoulder.[4] The flight membranes are brown and the ears are dark brown with a tuft of white fur at the base. The face is dark brown with a few long, stiff whiskers around the mouth.

The skull may be diagnosed by specific dental features. The second premolar and molars are markedly lobed. This feature is specific for this genus, and no other African fruit bats have this characteristic.

There is extreme sexual dimorphism in this species.[5] The male possesses an enormous head for producing loud honking calls.[5] The enlarged rostrum, larynx and lips allow these sounds to be extremely resonant. The larynx is one half the length of the vertebral column and fills out most of the thoracic cavity. It is nearly three times larger in males than females. The male also has a hairless split chin and warty rostrum with wrinkled skin around it. Females have a much more fox-like appearance similar to most fruit bats.[4]

Ecology and behavior[edit]

Hammer-headed bats are frugivores. Figs make up much of their diet, but they may also include mangos, bananas and guavas. There are some complications inherent in a fruit diet such as insufficient protein intake. It is suggested that fruit bats compensate for this by possessing a proportionally longer intestine compared to insectivorous species.[4] This enhances their ability to absorb protein. They also have very rapid digestive systems allowing these bats to assimilate high amounts of fruit to ensure that adequate protein is absorbed. It is also suggested that by eating a wide variety of fruits with varying protein contents, fruit bats are able to maintain an entirely frugivorous diet.[6]

Generally fruit is picked and taken to a nearby tree where it is chewed, the juice squeezed out and the pulp discarded. Since they often do not consume the pulp, these bats are not considered to be good seed distributors.[7] Males may forage long distances (up to 10 km) to locate the highest quality food. Females rely on established feeding routes that offer a constant supply of lower quality food. This may reflect different metabolic requirements based on body size differences.

Large bats often experience difficulties with overheating during flight. The limited thermoregulatory capabilities of flying bats appears to be one factor closely associated with why flight activity primarily occurs during cooler nocturnal temperatures. It has been found that hammer-headed bats are able to tolerate higher ambient temperatures during flight than other bats.[8] This ability is associated with this bat’s high thermal conductance (Cf) which is defined as the total heat loss less the heat loss due to evaporation divided by body temperature less the ambient temperature (Cf = [H1 – He]/[Tb – Ta]). However, they are especially sensitive to ambient temperatures below 11°C and a decrease in flight coordination is seen. Due to the large surface area of the wing, convective heat loss to cool air may be significant enough to chill flight muscles preventing the precise coordination essential for flight.

These bats are nocturnal, roosting during the day in the forest canopy. They rely on camouflage to hide them from predators.[4] Specific species of trees are not selected for roosting, however some roosts may be used for long periods of time. Roosts are generally 20–30 meters from the ground.

The main predators of this species are humans and nocturnal and diurnal birds of prey. However, infection by parasites is often the most significant problem for the hammer-headed bat. Adults are often infected with mites and the hepatoparasite, Hepatocystis carpenteri.

Reproduction and mortality[edit]

Little is known about reproduction in hammer-headed bats. In some populations breeding is thought to take place semi-annually during the dry seasons. The timing of the dry season varies depending on the locality, but in general there are two breeding seasons, one from June to August and the other from December to February.[4] However, in other populations, breeding is not restricted to dry seasons and occurs during all months of the year.

This species is often cited as a classic model of lek mating.[9] In this type of mating system, males cluster in dense groups at specific locations known as mating arenas.[9] In some populations of hammer-headed bats, males gather along rivers at night and display by rapid wing flapping accompanied by loud vocalizations.[10] An arena may contain from 25 to 132 males. Females fly through the arena assessing the males. Once the female’s choice is made, the female lands on the branch and sits beside the male. Once chosen, the male emits a buzzing call and copulation ensues.

However, some populations of hammer-headed bats do not use the lek mating strategy. Males actively display but are not found clustering in groups.[11] This species is highly polygamous. Some estimates suggest that as few as six percent of the males in a population account for up to seventy-nine percent of the matings.

Females generally produce one offspring at a time. Neither gestation nor time until weaning have been reported for this species. Females mature more quickly than males and are sexually mature after six months. They continue to grow and reach adult size at nine months. Males do not reach sexual maturity until approximately eighteen months of age and they do not obtain their unique facial morphology until twelve months. Compared with other bats, this bat is rather long-lived with an average life expectancy of thirty years in the wild.

Interactions with humans[edit]

H. monstrosus has no special conservation status. In 2004, the IUCN Red List of Threatened Species listed this species as LC (least concern) on the basis of its widespread distribution and lack of threats to its habitat.[1]

Due to this bat’s diet of fruit, it may be considered a crop pest. It has also been observed to attack live chickens.[12] This observation was reported once and cannot be considered a regular occurrence. Humans hunt this large bat and consume it as bushmeat.

The hammer-headed bat is one of three species of African fruit bat claimed to be asymptomatically infected with the Ebola virus.[13] It is not known whether these species are incidental hosts or a reservoir of Ebolavirus infection for humans and other terrestrial mammals.

References[edit]

  1. ^ a b S. Mickleburgh, A. M. Hutson, W. Bergmans & J. Fahr (2008). "Hypsignathus monstrosus". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. Retrieved February 2, 2010. 
  2. ^ Nowak M., R. (1994). Walker's Bats of the World. Johns Hopkins University Press. pp.63-64/
  3. ^ [1]
  4. ^ a b c d e Langevin, P., R. Barclay. 1990. "Hypsignathus monstrosus". Mammalian Species, 357: 1-4.
  5. ^ a b Altringham D., J. (1996). "Bats: Biology and Behaviour." Oxford University Press.
  6. ^ Courts S E. (1998) "Dietary strategies of Old World fruit bats (Megachiroptera, Pteropodidae): how do they obtain sufficient protein?" Mammal Rev. 28(4):185-194.
  7. ^ Eisenberg J F and Wilson D E. (1978) "Relative brain size and feeding strategies in the Chiroptera". Evolution, 32(4):740-751.
  8. ^ Carpenter R E. (1986) "Flight physiology of intermediate-sized fruit bats (Pteropodidae)". J Exp Biol. 120:79-103.
  9. ^ a b Bradbury W., J. (1977) "Lek Mating Behavior in the Hammer-headed Bat", Zeitschrift für Tierpsychologie, 45(3):225-255.
  10. ^ Griffin R., D. (1986). "Communication in the Chiroptera." JSTOR 61(2): 284.
  11. ^ Truxton G T. 2001. "The calling behavior and mating system of a non-lekking population of Hypsignathus monstrosus". Ph.D. dissertation. State University of New York at Stony Brook. 240 pages.
  12. ^ Deusen M. van, H. (1968). "Carnivorous Habits of Hypsignathus monstrosus " JSTOR 49(2): 335-336.
  13. ^ Brahic, C. (Nov. 30, 2005). "Fruit bats blamed for Ebola outbreaks."
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