Hammer-headed bat
Encyclopedia
The Hammer-headed Bat also known as the Big-lipped Bat, is a megabat
widely distributed in equator
ial Africa
. This large bat is found in riverine forests, mangrove
s, swamp
s, and palm forests at elevations less than 1800 meters.
Pelage is grey-brown to slaty-brown with a whitish collar of fur extending from shoulder to shoulder. 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. The male possesses an enormous head for producing loud honking calls. 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.
s. Fig
s make up much of their diet, but they may also include mango
s, banana
s and guava
s. 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. 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.
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. 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. 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. 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
.
This species is often cited as a classic model of lek mating. In this type of mating system, males cluster in dense groups at specific locations known as mating arenas. In some populations of hammer-headed bats, males gather along rivers at night and display by rapid wing flapping accompanied by loud vocalizations. 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. 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.
Due to this bat’s diet of fruit, it may be considered a crop pest. It has also been observed to attack live chickens. 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
. It is not known whether these species are incidental hosts or a reservoir of Ebolavirus infection for humans and other terrestrial mammals.
Megabat
Megabats constitute the suborder Megachiroptera, family Pteropodidae of the order Chiroptera . They are also called fruit bats, old world fruit bats, or flying foxes.-Description:...
widely distributed in equator
Equator
An equator is the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and containing the sphere's center of mass....
ial Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
. This large bat is found in riverine forests, mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
s, swamp
Swamp
A swamp is a wetland with some flooding of large areas of land by shallow bodies of water. A swamp generally has a large number of hammocks, or dry-land protrusions, covered by aquatic vegetation, or vegetation that tolerates periodical inundation. The two main types of swamp are "true" or swamp...
s, and palm forests at elevations less than 1800 meters.
Taxonomy
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
The hammer-headed bat is the largest bat in Africa with a wingspan of 686 to 970 millimeters. Males are significantly larger than females, averaging 400 grams while females average only 275 grams.Pelage is grey-brown to slaty-brown with a whitish collar of fur extending from shoulder to shoulder. 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
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
in this species. The male possesses an enormous head for producing loud honking calls. 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.
Ecology and behavior
Hammer-headed bats are frugivoreFrugivore
A frugivore is a fruit eater. It can be any type of herbivore or omnivore where fruit is a preferred food type. Because approximately 20% of all mammalian herbivores also eat fruit, frugivory is considered to be common among mammals. Since frugivores eat a lot of fruit they are highly dependent...
s. Fig
Common fig
The Common fig is a deciduous tree growing to heights of up to 6 m in the genus Ficus from the family Moraceae known as Common fig tree. It is a temperate species native to the Middle East.-Description:...
s make up much of their diet, but they may also include mango
Mango
The mango is a fleshy stone fruit belonging to the genus Mangifera, consisting of numerous tropical fruiting trees in the flowering plant family Anacardiaceae. The mango is native to India from where it spread all over the world. It is also the most cultivated fruit of the tropical world. While...
s, banana
Banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....
s and guava
Guava
Guavas are plants in the myrtle family genus Psidium , which contains about 100 species of tropical shrubs and small trees. They are native to Mexico, Central America, and northern South America...
s. 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. 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.
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
Seed
A seed is a small embryonic plant enclosed in a covering called the seed coat, usually with some stored food. It is the product of the ripened ovule of gymnosperm and angiosperm plants which occurs after fertilization and some growth within the mother plant...
distributors. 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. 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
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
canopy
Canopy (forest)
In biology, the canopy is the aboveground portion of a plant community or crop, formed by plant crowns.For forests, canopy also refers to the upper layer or habitat zone, formed by mature tree crowns and including other biological organisms .Sometimes the term canopy is used to refer to the extent...
. They rely on camouflage to hide them from predators. 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
Diurnal animal
Diurnality is a plant or animal behavior characterized by activity during the day and sleeping at night.-In animals:Animals that are not diurnal might be nocturnal or crepuscular . Many animal species are diurnal, including many mammals, insects, reptiles and birds...
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
Hepatocystis carpenteri
Hepatocystis carpenteri Miltgen, Landau and Bradbury, 1980 is a species of the genus Hepatocystis.Species in this genus are parasitic protozoa transmitted by flies of the genus Culicoides and infect mammals.-Description:...
.
Reproduction and mortality
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. 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. In this type of mating system, males cluster in dense groups at specific locations known as mating arenas. In some populations of hammer-headed bats, males gather along rivers at night and display by rapid wing flapping accompanied by loud vocalizations. 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. 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
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.Due to this bat’s diet of fruit, it may be considered a crop pest. It has also been observed to attack live chickens. 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
Ebola virus
Ebola virus causes severe disease in humans and in nonhuman primates in the form of viral hemorrhagic fever. EBOV is a Select Agent, World Health Organization Risk Group 4 Pathogen , National Institutes of Health/National Institute of Allergy and Infectious Diseases Category A Priority Pathogen,...
. It is not known whether these species are incidental hosts or a reservoir of Ebolavirus infection for humans and other terrestrial mammals.
External links
- Hammer-headed Bat, at Wild World from the World Wide Fund for NatureWorld Wide Fund for NatureThe World Wide Fund for Nature is an international non-governmental organization working on issues regarding the conservation, research and restoration of the environment, formerly named the World Wildlife Fund, which remains its official name in Canada and the United States...
. - A picture of the facial morphology of the male on the VPROVPROThe VPRO was established in the Netherlands in 1926 as a religious broadcasting organization. Falling under the Protestant pillar, it represented the Liberal Protestant current...
website, from Noorderlicht, a Dutch science magazine program. - Lateral and anterior views of the male and female skull, from Biolib, an international encyclopedia of plants, fungi and animals.