Hammer-headed bat | |
---|---|
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Chiroptera |
Family: | Pteropodidae |
Genus: | Hypsignathus H. Allen, 1861 |
Species: | H. monstrosus |
Binomial name | |
Hypsignathus monstrosus H. Allen, 1861 | |
Hammer-headed bat range | |
Synonyms | |
|
The hammer-headed bat (Hypsignathus monstrosus), also known as hammer-headed fruit bat, big-lipped bat, and hammerhead bat, [2] [3] is a megabat widely distributed in West and Central Africa. It is the only member of the genus Hypsignathus, which is part of the tribe Epomophorini along with four other genera. It is the largest bat in continental Africa, with wingspans approaching 1 m (3.3 ft), and males are almost twice as heavy as females. Males and females also greatly differ in appearance, making it the most sexually dimorphic bat species in the world. These differences include several adaptations that help males produce and amplify vocalizations: the males' larynges (vocal cords) are about three times as large as those of females, and they have large resonating chambers on their faces. Females appear more like a typical megabat, with foxlike faces.
The hammer-headed bat is frugivorous, consuming a variety of fruits such as figs, bananas, and mangoes, though a few instances of carnivory have been noted. Females tend to travel a consistent route to find predictable fruits, whereas males travel more to find the highest quality fruit. It forages at night, sleeping during the day in tree roosts. Individuals may roost alone or in small groups. Unlike many other bat species that segregate based on sex, males and females will roost together during the day. It has two mating seasons each year during the dry seasons. It is believed to be the only bat species with a classical lek mating system, wherein males gather on a "lek", which in this case is a long and thin stretch of land, such as along a river. There, they produce loud, honking vocalizations to attract females. Females visit the lek and select a male to mate with; the most successful 6% of males are involved in 79% of matings. Offspring are born five or six months later, typically a singleton, though twins have been documented. Its predators are not well-known, but may include hawks. Adults are commonly affected by parasites such as flies and mites.
The hammer-headed bat is sometimes considered a pest due to its frugivorous diet and its extremely loud honking noises at night. In Nigeria and the Democratic Republic of the Congo, it is consumed as bushmeat. It has been investigated as a potential reservoir of the Ebola virus, with several testing positive for antibodies against the virus. It is not considered a species of conservation concern due to its large range and presumably large population size.
Position of Hypsignathus within Pteropodidae [4] |
The hammer-headed bat was described as a new species in 1861 by American scientist Harrison Allen. Allen placed the species into a newly-created genus, Hypsignathus. [5] The holotype had been collected by French-American zoologist Paul Du Chaillu [5] in Gabon. [6] The genus name Hypsignathus comes from the Ancient Greek ὕψος (húpsos, 'high'), and γνάθος (gnáthos, 'jaw'). T. S. Palmer speculated that Allen chose the name Hypsignathus to allude to the "deeply arched mouth" of the species. [7] The species name monstrosus is Latin for "having the qualities of a monster". [8]
A 2011 study found that Hypsignathus was the most basal member of the tribe Epomophorini, which also includes Epomops , Micropteropus , Epomophorus , and Nanonycteris . [4] Initially, Allen identified the hammer-headed bat as a member of the subfamily Pteropodinae of the megabats. [5] However, in 1997, Epomophorini was recognized as part of the subfamily Epomophorinae. [9] Some taxonomists do not recognize Epomophorinae as a valid subfamily and include its taxa, including the Epomophorini, within Rousettinae. [10] [11]
The hammer-headed bat is the largest bat in mainland Africa. [12] Males have wingspans up to 90.1 cm (2.96 ft), [13] and all individuals have forearm lengths exceeding 112 mm (4.4 in). [12] It has pronounced sexual dimorphism, more so than any other bat species in the world, [12] with males up to twice as heavy as females. The average weight of males is 420 g (15 oz), compared to 234 g (8.3 oz) for females. [13] Other differences between the sexes relate to their social system, in which males produce loud, honking vocalizations. Therefore, males have greatly enlarged larynges, about three times the size of females', [14] extending through most of the thoracic cavity, and measuring half the length of the spine. The larynx is so large, it displaces other organs, including the heart, lungs, and gastrointestinal tract. [14] Males also have resonating chambers to increase the volume of sound production. These chambers are pharyngeal air sacs connected to a large sinus in the humped snout. [12] These numerous adaptations caused scientists Herbert Lang and James Chapin to remark, "In no other mammal is everything so entirely subordinated to the organs of voice". [15]
Males overall have boxy heads with enormous lips, while the females, with their narrower snouts, have more foxlike faces. [14] Males and females both have dark brown fur, with a paler mantle (sides and back of neck). It has patches of white fur at the base of the ears, though sometimes indistinct. The fur is long and smooth, though somewhat woolly in texture on the mantle. The ears are triangular and blackish-brown, and the eyes are very large. [12] The dental formula is 2.1.2.12.1.3.2 for a total of 28 teeth; very occasionally, individuals have been found with an additional upper premolar on each side of the mouth, for a total of 30 teeth. The skull is larger and more robust than any other megabat in Africa, with a pronounced, massive snout. The tongue is large and powerful, with an expanded, tridentate tip. The tongue has backwards-facing papillae used to extract juice from fruits. [12]
The wings are characterized by low aspect ratio, meaning that it has a smaller wingspan relative to the wing area. The wing loading is considered exceptionally high, meaning that it has a large body weight relative to the wing area. The wings are blackish brown in color. [12] The thumb is approximately 128–137 mm (5.0–5.4 in) long. [14] The wings attach to the hindlimbs at the second toe. It lacks a tail. [12]
Instead of the typical mammalian karyotype where females have two X chromosomes and males have one each of X and Y, males have a single X chromosome and no Y chromosome, known as X0 sex-determination system. [12] Thus, females have 36 chromosomes (34 autosomes and two sex chromosomes), and males have 35 chromosomes (34 autosomes but only one sex chromosome). [16] This is seen in a few other bat genera, including Epomophorus and Epomops . [17] [18]
Hammer-headed bats are frugivores. Figs make up much of their diet, but mangos, bananas and guavas may also be consumed. 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. [14]
Males and females rely on different strategies for foraging. Females use trap-lining, in which they travel an established route with dependable and predictable food sources, even if the food is lower quality. Males, in contrast, search for areas rich with food, traveling up to 10 km (6.2 mi) to reach particularly good food patches. [14] Upon finding suitable fruit, the hammer-headed bat may eat at the tree or pick the fruit and carry it away to another site for consumption. It chews the fruit, swallowing the juice and soft pulp, before spitting out the rest. [14] The guano (feces) typically contains seeds from ingested fruits, indicating that it may be an important seed disperser. [12]
Van Deusan (1968) reports H. monstrosus showing some carnivorous behavior by attacking chickens to drink their blood and scavenging for meat. [19]
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 the first breeding season is from June to August and the second is from December to February. Females may become pregnant up to twice per year, giving birth after five or six months gestation [12] to one offspring at a time, [14] though twins have been reported. [15] Newborns weigh approximately 40 g (1.4 oz) at birth. [15] Females reach sexual maturity faster than males, and can reproduce at six months. Females reach adult size by nine months of age. In contrast, males are not sexually mature until eighteen months. Males and females are similar in size for their first year of life. [14]
This species is often cited as an example of classical lek mating, [20] and is perhaps the only bat species with such. [21] The classical lek is defined by four criteria: [12]
Males form these leks along streams or riverbeds during the mating season, which lasts 1–3 months. [14] Leks consist of 20–135 males in an area about 40 m (130 ft) wide and 400–1,600 m (1,300–5,200 ft) long. [12] Each male claims a display territory of about 10 m (33 ft) in diameter, [13] in which he honks repeatedly and flaps his wings while hanging from a branch. [14] Typically, 60–120 honks are produced per minute. [20] Males display for around four hours before foraging, with peaks in lekking activity in the early evening and before dawn. The early evening peak is when the majority of copulation occurs. Females will fly through the lek, selecting a male by landing on a branch next to him. The chosen male emits a "staccato buzz" call, followed immediately by copulation, which lasts 30–60 seconds. [14] After copulation, the female immediately departs, and the male resumes displaying. [12] The males at the center of the lek have the most success, and are responsible for the majority of matings: [14] the top 6% of males have 79% of the total matings. [12] In the before-dawn peak in activity, copulation is less frequent, and males spend time jockeying with each other for the best display territory. As the mating season progresses, the importance of the before-dawn peak lessens. [14]
However, some populations of hammer-headed bats in West Africa do not use leks. Instead, they have a harem system. [22]
During the day, the hammer-headed bat roosts in trees, typically 20–30 m (66–98 ft) above the ground in the forest canopy. Various trees are used for roosting, with no preference for a particular species. It has low fidelity to its roost and will move to a new roost after 5–9 days. [12] It relies on camouflage to hide from predators. [14] It displays a mix of solitary and social behavior. Individuals of both sexes are frequently found roosting alone, though they may roost in small groups of around four individuals. Occasionally, groups of up to twenty-five have been documented. Groups are of mixed sex and age, unlike other bat species which segregate based on sex. While roosting, individuals in a group are approximately 10–15 cm (3.9–5.9 in) apart, with males on the periphery and females nearer the center. [12] During most of the day, individuals sleep with their noses covered by their wings. [20] Members of the same group show little interaction with each other: they do not "squabble", vocalize, or groom each other. Instead, at sunset, individuals groom themselves then set off independently to forage. [12]
Its predators are not well-documented, but may include avian species such as the long-tailed hawk. [23] It has a diverse array of parasites, including such ectoparasites as the bat fly (Nycteribiidae) Dipseliopoda arcuata , the spinturnicid mite Ancystropus aethiopicus , the gastronyssid mite Mycteronyssus polli , and the teinocoptid mite Teinocopties auricularis . [12] Internally, it is known to be affected by the liver parasite Hepatocystis carpenteri . Adults commonly host parasites. [14]
The hammer-headed bat is a lowland species, always occurring below 1,800 m (5,900 ft) above sea level. [14] Most records of this species occur in rainforest habitat, including lowland rainforest, swamp forest, riverine forests, and mosaics of forest and grassland. While it has been documented in savanna habitats, these records are rare, and it has been speculated that these individuals are vagrants. [12] It has a wide range in West and Central Africa, including the following countries: Angola, Benin, Burkina Faso, Cameroon, Central African Republic, Republic of the Congo, Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Ethiopia, Gabon, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Nigeria, Sierra Leone, Sudan, Togo, and Uganda. [1]
As a frugivorous species, the hammer-headed bat is sometimes considered a pest of fruit crops. [24] Its ability to produce extremely loud vocalizations means that some consider it one of Africa's most significant nocturnal pests. [12] Humans hunt this large bat and consume it as bushmeat. [24] It is eaten in Nigeria, [25] as well as seasonally in the Democratic Republic of the Congo. [26]
The hammer-headed bat has been investigated as a potential reservoir of the Ebola virus. Some individuals have tested seropositive for the virus, meaning that they had antibodies against the virus, though the virus itself was not detected. Additionally, nucleic acid sequences associated with the virus have been isolated from its tissues. [27] However, the natural reservoirs of ebolaviruses are still unknown as of 2019. [28] [29] [30] Megabats like the hammer-headed bat tend to be over-sampled relative to other potential Ebola virus hosts, meaning that they may have an unwarranted amount of research attention, and as of 2015 [update] , no bat hunter or researcher is known to be the index case ("patient zero") in an Ebola outbreak. [31]
As of 2016 [update] , the hammer-headed bat is evaluated as a least-concern species by the IUCN —its lowest conservation priority. It meets the criteria for this classification because it has a wide geographic range; its population is presumably large; and it is not thought to be experiencing rapid population decline. [1] It is not a common bat species in captivity, though it is kept at the Wrocław Zoo in Poland as of 2020, [32] and was kept at the Bronx Zoo and San Diego Zoo Safari Park in the 1970s and 1980s. In captivity, hammer-headed bats, particularly males, are vulnerable to stress-related illness, especially when moved or placed in new enclosures. [33]
Megabats constitute the family Pteropodidae of the order Chiroptera (bats). They are also called fruit bats, Old World fruit bats, or—especially the genera Acerodon and Pteropus—flying foxes. They are the only member of the superfamily Pteropodoidea, which is one of two superfamilies in the suborder Yinpterochiroptera. Internal divisions of Pteropodidae have varied since subfamilies were first proposed in 1917. From three subfamilies in the 1917 classification, six are now recognized, along with various tribes. As of 2018, 197 species of megabat had been described.
Bushmeat is meat from wildlife species that are hunted for human consumption. Bushmeat represents a primary source of animal protein and a cash-earning commodity in poor and rural communities of humid tropical forest regions of the world.
Horseshoe bats are bats in the family Rhinolophidae. In addition to the single living genus, Rhinolophus, which has about 106 species, the extinct genus Palaeonycteris has been recognized. Horseshoe bats are closely related to the Old World leaf-nosed bats, family Hipposideridae, which have sometimes been included in Rhinolophidae. The horseshoe bats are divided into six subgenera and many species groups. The most recent common ancestor of all horseshoe bats lived 34–40 million years ago, though it is unclear where the geographic roots of the family are, and attempts to determine its biogeography have been indecisive. Their taxonomy is complex, as genetic evidence shows the likely existence of many cryptic species, as well as species recognized as distinct that may have little genetic divergence from previously recognized taxa. They are found in the Old World, mostly in tropical or subtropical areas, including Africa, Asia, Europe, and Oceania.
The Egyptian fruit bat or Egyptian rousette is a species of megabat that occurs in Africa, the Middle East, the Mediterranean and the Indian subcontinent. It is one of three Rousettus species with an African-Malagasy range, though the only species of its genus found on continental Africa. The common ancestor of the three species colonized the region in the late Pliocene or early Pleistocene. The species is traditionally divided into six subspecies. It is considered a medium-sized megabat, with adults weighing 80–170 g (2.8–6.0 oz) and possessing wingspans of approximately 60 cm (24 in). Individuals are dark brown or grayish brown, with their undersides paler than their backs.
The grey-headed flying fox is a megabat native to Australia. The species shares mainland Australia with three other members of the genus Pteropus: the little red P. scapulatus, spectacled P. conspicillatus, and the black P. alecto. The grey-headed flying fox is the largest bat in Australia.
The XO sex-determination system is a system that some species of insects, arachnids, and mammals use to determine the sex of offspring. In this system, there is only one sex chromosome, referred to as X. Males only have one X chromosome (XO), while females have two (XX). The letter O signifies the lack of a Y chromosome. Maternal gametes always contain an X chromosome, so the sex of the animals' offspring depends on whether a sex chromosome is present in the male gamete. Its sperm normally contains either one X chromosome or no sex chromosomes at all.
The Sulawesi flying fox or Sulawesi fruit bat is a species of megabat endemic to Indonesia. It is classified as "Vulnerable" by the IUCN due to unsustainable levels of hunting.
The greater short-nosed fruit bat, or short-nosed Indian fruit bat, is a species of megabat in the family Pteropodidae found in South and Southeast Asia.
The straw-coloured fruit bat 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. It is listed 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. From October to end of December every year, in the largest migration of mammals on the planet, up to 10 million straw-coloured fruit bats congregate in Kasanka National Park, Zambia, roosting in a 2 hectares area of Mushitu forest each day. This migration was only discovered in 1980. Their necks and backs are a yellowish-brown colour, while their undersides are tawny olive or brownish.
The Ethiopian epauletted fruit bat is a species of megabat in the family Pteropodidae. It is found in Burundi, Chad, Republic of the Congo, Democratic Republic of the Congo, Eritrea, Ethiopia, Kenya, Malawi, Mozambique, Nigeria, Rwanda, Sudan, Tanzania, and Uganda. Its natural habitat is savanna.
Wahlberg's epauletted fruit bat is a species of megabat in the family Pteropodidae. It is commonly found across southern Africa.
Buettikofer's epauletted fruit bat is a species of megabat in the family Pteropodidae. It is found in Ivory Coast, Ghana, Guinea, Guinea-Bissau, Liberia, Nigeria, Senegal, and Sierra Leone. Its natural habitats are subtropical or tropical moist lowland forest and savanna.
Peters's dwarf epauletted fruit bat is a species of megabat in the family Pteropodidae. It is found in Angola, Benin, Burkina Faso, Burundi, Cameroon, Central African Republic, Chad, Republic of the Congo, Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Mali, Niger, Nigeria, Rwanda, Senegal, Sierra Leone, Sudan, Tanzania, Togo, Uganda, and Zambia. Its natural habitats are subtropical or tropical moist lowland forests and moist savanna.
The little collared fruit bat is a species of megabat in the family Pteropodidae found in Angola, Cameroon, the Central African Republic, the Republic of the Congo, the Democratic Republic of the Congo, Ivory Coast, Equatorial Guinea, Gabon, Ghana, Guinea, Liberia, Nigeria, Rwanda, Sierra Leone, South Sudan, Togo, and Uganda. Its natural habitats are subtropical or tropical moist lowland forests and moist savanna.
The Indian flying fox, also known as the greater Indian fruit bat, is a species of flying fox native to the Indian subcontinent. It is one of the largest bats in the world. It is of interest as a disease vector, as it is capable of transmitting several viruses to humans. It is nocturnal and feeds mainly on ripe fruits, such as mangoes and bananas, and nectar. This species is often regarded as vermin due to its destructive tendencies towards fruit farms, but the benefits of its pollination and seed propagation often outweigh the impacts of its fruit consumption.
The Madagascan flying fox, Madagascar flying-fox, or Madagascar fruit bat is a species of megabat in the genus Pteropus. It is endemic to Madagascar. Its natural habitats are diverse, and include moist lowland forests, dry forests, succulent woodlands, and spiny thickets, and mangroves. It eats figs and other fruits, flowers, and leaves. It is threatened by habitat loss.
The large flying fox, also known as the greater flying fox, Malayan flying fox, Malaysian flying fox, large fruit bat, kalang, or kalong, is a southeast Asian species of megabat in the family Pteropodidae. Despite its scientific name, it feeds exclusively on fruits, nectar, and flowers, like the other flying foxes of the genus Pteropus. It is noted for being one of the largest bats. As with nearly all other Old World fruit bats, it lacks the ability to echolocate but compensates for it with well-developed eyesight.
Bats are flying mammals of the order Chiroptera. With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most birds, flying with their very long spread-out digits covered with a thin membrane or patagium. The smallest bat, and arguably the smallest extant mammal, is Kitti's hog-nosed bat, which is 29–34 mm (1.1–1.3 in) in length, 150 mm (5.9 in) across the wings and 2–2.6 g (0.071–0.092 oz) in mass. The largest bats are the flying foxes, with the giant golden-crowned flying fox reaching a weight of 1.6 kg (3.5 lb) and having a wingspan of 1.7 m.
Bats as food are eaten by people in some areas of North America, Asia, Africa, Pacific Rim countries, and some other cultures, including the United States, China, Vietnam, the Seychelles, the Philippines, Indonesia, Palau, Thailand, and Guam. Half the megabat species are hunted for food but only eight percent of the insectivorous bat species are. In Guam, Mariana fruit bats are considered a delicacy.
The Rousettinae are a subfamily of megabats. Taxa within this subfamily include:
{{cite book}}
: CS1 maint: multiple names: authors list (link){{cite book}}
: CS1 maint: multiple names: authors list (link)Scientists do not know where Ebola virus comes from.
Despite concerted investigative efforts, the natural reservoir of the virus is unknown.
The geographic ranges of many animal species, including bats, squirrels, mice and rats, dormice, and shrews, match or overlap with known outbreak sites of African filoviruses, but none of these mammals has yet been universally accepted as an EBOV reservoir.