Megabat

Taxonomic history }} |1=Scotonycterini |2= }} }} }} }} The family Pteropodidae was first described in 1821 by British zoologist John Edward Gray. He named the family "Pteropidae" (after the genus Pteropus) and placed it within the now-defunct order Fructivorae. Fructivorae contained one other family, the now-defunct Cephalotidae, containing one genus, Cephalotes Gray's spelling was possibly based on a misunderstanding of the suffix of "Pteropus". "Pteropus" comes from Ancient Greek meaning "wing" and meaning "foot". The Greek word pous of Pteropus is from the stem word pod-; therefore, Latinizing Pteropus correctly results in the prefix "Pteropod-". French biologist Charles Lucien Bonaparte was the first to use the corrected spelling Pteropodidae in 1838. Dobson selected these names to allude to the body size differences of the two groups, with many fruit-eating bats being larger than insect-eating bats. Pteropodidae was the only family he included within Megachiroptera. Since 2005, this suborder has alternatively been called "Pteropodiformes". Two superfamilies comprise Yinpterochiroptera: Rhinolophoidea—containing the above families formerly in Microchiroptera—and Pteropodoidea, which only contains Pteropodidae. In 1917, Danish mammalogist Knud Andersen divided Pteropodidae into three subfamilies: Macroglossinae, Pteropinae (corrected to Pteropodinae), and Harpyionycterinae. A 1995 study found that Macroglossinae as previously defined, containing the genera Eonycteris, Notopteris, Macroglossus, Syconycteris, Melonycteris, and Megaloglossus, was paraphyletic, meaning that the subfamily did not group all the descendants of a common ancestor. Subsequent publications consider Macroglossini as a tribe within Pteropodinae that contains only Macroglossus and Syconycteris. In 1984, an additional pteropodid subfamily, Propottininae, was proposed, representing one extinct species described from a fossil discovered in Africa, Propotto leakeyi. In 2018 the fossils were reexamined and determined to represent a lemur. As of 2018, there were 197 described species of megabat, around a third of which are flying foxes of the genus Pteropus. Evolutionary history Fossil record and divergence times bat Archaeopteropus evolved a very similar morphology to pteropodids, but its taxonomic affinities remain controversial The fossil record for pteropodid bats is the most incomplete of any bat family. Although the poor skeletal record of Chiroptera is probably from how fragile bat skeletons are, Pteropodidae still have the most incomplete despite generally having the biggest and most sturdy skeletons. It is also surprising that Pteropodidae are the least represented because they were the first major group to diverge. Several factors could explain why so few pteropodid fossils have been discovered: tropical regions where their fossils might be found are under-sampled relative to Europe and North America; conditions for fossilization are poor in the tropics, which could lead to fewer fossils overall; and even when fossils are formed, they may be destroyed by subsequent geological activity. It is estimated that more than 98% of pteropodid fossil history is missing. Even without fossils, the age and divergence times of the family can still be estimated by using computational phylogenetics. Pteropodidae split from the superfamily Rhinolophoidea (which contains all the other families of the suborder Yinpterochiroptera) approximately 58 Mya (million years ago). However, the presence of a bony calcar, which is not present in pteropodids, suggests that it may not belong to this group. Although the head and teeth are too poorly-preserved to deduce its diet, it also may potentially display adaptations for an insectivorous rather than a frugivorous lifestyle. The taxonomic affiliation of Archaeopteropus still remains contentious. Excluding Archaeopteropus, the oldest known fossil record of pteropodids are isolated teeth recovered from the Late Eocene-aged Wai Lek pit of the Krabi Basin in Thailand. Biogeography The family Pteropodidae likely originated in Australasia based on biogeographic reconstructions. the cynopterines likely originated on the Sunda Shelf based on results of a Weighted Ancestral Area Analysis of six nuclear and mitochondrial genes. From these regions, pteropodids colonized other areas, including continental Asia and Africa. Megabats reached Africa in at least four distinct events. The four proposed events are represented by (1) Scotonycteris, (2) Rousettus, (3) Scotonycterini, and (4) the "endemic Africa clade", which includes Stenonycterini, Plerotini, Myonycterini, and Epomophorini, according to a 2016 study. It is unknown when megabats reached Africa, but several tribes (Scotonycterini, Stenonycterini, Plerotini, Myonycterini, and Epomophorini) were present by the Late Miocene. How megabats reached Africa is also unknown. It has been proposed that they could have arrived via the Middle East before it became more arid at the end of the Miocene. Conversely, they could have reached the continent via the Gomphotherium land bridge, which connected Africa and the Arabian Peninsula to Eurasia. The genus Pteropus (flying foxes), which is not found on mainland Africa, is proposed to have dispersed from Melanesia via island hopping across the Indian Ocean; this is less likely for other megabat genera, which have smaller body sizes and thus have more limited flight capabilities. A 2017 study of bat ontogeny (embryonic development) found evidence that megabat embryos at first have large, developed cochlea similar to echolocating microbats, though at birth they have small cochlea similar to non-echolocating mammals. This evidence supports that laryngeal echolocation evolved once among bats, and was lost in pteropodids, rather than evolving twice independently. Megabats in the genus Rousettus are capable of primitive echolocation through clicking their tongues. Some species—the cave nectar bat (Eonycteris spelaea), lesser short-nosed fruit bat (Cynopterus brachyotis), and the long-tongued fruit bat (Macroglossus sobrinus)—have been shown to create clicks similar to those of echolocating bats using their wings. Both echolocation and flight are energetically expensive processes separately, although no increase in flight energy expenditure was found for two species of echolocating bats compared with other bats and birds . Echolocating bats couple sound production with the mechanisms engaged for flight, allowing them to reduce the additional energy burden of echolocation. Instead of pressurizing a bolus of air for the production of sound, laryngeally echolocating bats likely use the force of the downbeat of their wings to pressurize the air, cutting energetic costs by synchronizing wingbeats and echolocation. The loss of echolocation (or conversely, the lack of its evolution) may be due to the uncoupling of flight and echolocation in megabats. ==Description==

Appearance (Pteropus mariannus) Megabats take their name from their larger weight and size; the largest, the great flying fox (Pteropus neohibernicus), weighs up to ; some members of Acerodon and Pteropus have wingspans reaching up to . The flying foxes of Pteropus and Acerodon are often taken as exemplars of the whole family in terms of body size. In reality, these genera are outliers, creating a misconception of the true size of most megabat species. The simple appearance of the ear is due in part to the lack of tragi (cartilage flaps projecting in front of the ear canal), which are found in many microbat species. Megabats of the genus Nyctimene appear less dog-like, with shorter faces and tubular nostrils. Unlike microbats, megabats have a greatly reduced uropatagium, which is an expanse of flight membrane that runs between the hind limbs. Most megabat wings insert laterally (attach to the body directly at the sides). In Dobsonia species, the wings attach nearer the spine, giving them the common name of "bare-backed" or "naked-backed" fruit bats. The length of the snout varies among genera. The premaxilla is well-developed and usually free, The premaxilla always lack a palatal branch. Megabat species have relatively small incisors and large canines. The premolars and molars are adapted to crush and pierce fruit, their primary food source. The most complete dental formula is: I2/2, C 1/1, P3/3, M2/3 x 2 = 34. The dental formula of 34 teeth is a homologous trait for megabats. This makes it the only mammal species with an asymmetrical dental formula. Megabat molars and premolars are simplified, with a reduction in the cusps and ridges resulting in a more flattened crown. the deciduous set does not include molars. to the skin. only Eonycteris, Dobsonia, Notopteris, and Neopteryx lack the second claw. The first digit is the shortest, while the third digit is the longest. The second digit is incapable of flexion. The entire leg is rotated at the hip compared to normal mammal orientation, meaning that the knees face posteriorly. All five digits of the foot flex in the direction of the sagittal plane, with no digit capable of flexing in the opposite direction, as in the feet of perching birds. Internal systems (Hypsignathus monstrosus) Flight is very energetically expensive, requiring several adaptations to the cardiovascular system. During flight, bats can raise their oxygen consumption by twenty times or more for sustained periods; human athletes can achieve an increase of a factor of twenty for a few minutes at most. A 1994 study of the straw-coloured fruit bat (Eidolon helvum) and hammer-headed bat (Hypsignathus monstrosus) found a mean respiratory exchange ratio (carbon dioxide produced:oxygen used) of approximately 0.78. Among these two species, the gray-headed flying fox (Pteropus poliocephalus) and the Egyptian fruit bat (Rousettus aegyptiacus), maximum heart rates in flight varied between 476 beats per minute (gray-headed flying fox) and 728 beats per minute (Egyptian fruit bat). The maximum number of breaths per minute ranged from 163 (gray-headed flying fox) to 316 (straw-colored fruit bat). Additionally, megabats have exceptionally large lung volumes relative to their sizes. While terrestrial mammals such as shrews have a lung volume of 0.03 cm3 per gram of body weight (0.05 in3 per ounce of body weight), species such as the Wahlberg's epauletted fruit bat (Epomophorus wahlbergi) have lung volumes 4.3 times greater at 0.13 cm3 per gram (0.22 in3 per ounce). The digestive system is structured to a herbivorous diet sometimes restricted to soft fruit or nectar. ==Biology and ecology==

Genome size Like all bats, megabats have much smaller genomes than other mammals. A 2009 study of 43 megabat species found that their genomes ranged from 1.86 picograms (pg, 978 Mbp per pg) in the straw-colored fruit bat to 2.51 pg in Lyle's flying fox (Pteropus lylei). All values were much lower than the mammalian average of 3.5 pg. Megabats have even smaller genomes than microbats, with a mean weight of 2.20 pg compared to 2.58 pg. It was speculated that this difference could be related to the fact that the megabat lineage has experienced an extinction of the LINE1—a type of long interspersed nuclear element. LINE1 constitutes 15–20% of the human genome and is considered the most prevalent long interspersed nuclear element among mammals. Senses Sight (Mirimiri acrodonta) With very few exceptions, megabats do not echolocate, and therefore rely on sight and smell to navigate. Megabat irises are usually brown, but they can be red or orange, as in Desmalopex, Mirimiri, Pteralopex, and some Pteropus. At high brightness levels, megabat visual acuity is poorer than that of humans; at low brightness it is superior. One study that examined the eyes of some Rousettus, Epomophorus, Eidolon, and Pteropus species determined that the first three genera possess a tapetum lucidum, a reflective structure in the eyes that improves vision at low light levels, while the Pteropus species do not. Smell (Nyctimene major) Megabats use smell to find food sources like fruit and nectar. Tube-nosed fruit bats such as the eastern tube-nosed bat (Nyctimene robinsoni) have stereo olfaction, meaning they are able to map and follow odor plumes three-dimensionally. In flying foxes, males have enlarged androgen-sensitive sebaceous glands on their shoulders they use for scent-marking their territories, particularly during the mating season. The secretions of these glands vary by species—of the 65 chemical compounds isolated from the glands of four species, no compound was found in all species. Taste Megabats possess the TAS1R2 gene, meaning they have the ability to detect sweetness in foods. This gene is present among all bats except vampire bats. Like all other bats, megabats cannot taste umami, due to the absence of the TAS1R1 gene. Among other mammals, only giant pandas have been shown to lack this gene. Reproduction and life cycle (Pteropus lylei) with offspring Megabats, like all bats, are long-lived relative to their size for mammals. Some captive megabats have had lifespans exceeding thirty years. Gestation length is variable, The post-implantation delay means that development of the embryo is suspended for up to eight months after implantation in the uterine wall, which is responsible for its very long pregnancies. The litter size of all megabats is usually one. There are scarce records of twins in the following species: Madagascan flying fox (Pteropus rufus), Dobson's epauletted fruit bat (Epomops dobsoni), the gray-headed flying fox, the black flying fox (Pteropus alecto), the spectacled flying fox (Pteropus conspicillatus), the greater short-nosed fruit bat, Peters's epauletted fruit bat (Epomophorus crypturus), the hammer-headed bat, the straw-colored fruit bat, the little collared fruit bat (Myonycteris torquata), the Egyptian fruit bat, and Leschenault's rousette (Rousettus leschenaultii). At birth, megabat offspring are, on average, 17.5% of their mother's post-partum weight. This is the smallest offspring-to-mother ratio for any bat family; across all bats, newborns are 22.3% of their mother's post-partum weight. Megabat offspring are not easily categorized into the traditional categories of altricial (helpless at birth) or precocial (capable at birth). Species such as the greater short-nosed fruit bat are born with their eyes open (a sign of precocial offspring), whereas the Egyptian fruit bat offspring's eyes do not open until nine days after birth (a sign of altricial offspring). As with nearly all bat species, males do not assist females in parental care. The young stay with their mothers until they are weaned; how long weaning takes varies throughout the family. Megabats, like all bats, have relatively long nursing periods: offspring will nurse until they are approximately 71% of adult body mass, compared to 40% of adult body mass in non-bat mammals. Species in the genus Micropteropus wean their young by seven to eight weeks of age, whereas the Indian flying fox (Pteropus medius) does not wean its young until five months of age. Very unusually, male individuals of two megabat species, the Bismarck masked flying fox (Pteropus capistratus) and the Dayak fruit bat (Dyacopterus spadiceus), have been observed producing milk, but there has never been an observation of a male nursing young. It is unclear if the lactation is functional and males actually nurse pups or if it is a result of stress or malnutrition. Behavior and social systems Many megabat species are highly gregarious or social. Megabats will vocalize to communicate with each other, creating noises described as "trill-like bursts of sound", honking, or loud, bleat-like calls in various genera. At least one species, the Egyptian fruit bat, is capable of a kind of vocal learning called vocal production learning, defined as "the ability to modify vocalizations in response to interactions with conspecifics". Young Egyptian fruit bats are capable of acquiring a dialect by listening to their mothers, as well as other individuals in their colonies. It has been postulated that these dialect differences may result in individuals of different colonies communicating at different frequencies, for instance. Megabat social behavior includes using sexual behaviors for more than just reproduction. Evidence suggests that female Egyptian fruit bats take food from males in exchange for sex. Paternity tests confirmed that the males from which each female scrounged food had a greater likelihood of fathering the scrounging female's offspring. Homosexual fellatio has been observed in at least one species, the Bonin flying fox (Pteropus pselaphon). This same-sex fellatio is hypothesized to encourage colony formation of otherwise-antagonistic males in colder climates. A few island species and subspecies are diurnal, hypothesized as a response to a lack of predators. Diurnal taxa include a subspecies of the black-eared flying fox (Pteropus melanotus natalis), the Mauritian flying fox (Pteropus niger), the Caroline flying fox (Pteropus molossinus), a subspecies of Pteropus pelagicus (P. p. insularis), and the Seychelles fruit bat (Pteropus seychellensis). In Australia, Eucalyptus flowers are an especially important food source. They are prodigious eaters and can consume up to 2.5 times their own body weight in fruit per night. Megabats fly to roosting and foraging resources. They typically fly straight and relatively fast for bats; some species are slower with greater maneuverability. Species can commute in a night. Migratory species of the genera Eidolon, Pteropus, Epomophorus, Rousettus, Myonycteris, and Nanonycteris can migrate distances up to . Most megabats have below-average aspect ratios, which is measurement relating wingspan and wing area. A study on the island provided the first systematic analysis of the species' feeding habits, mainly through the examination of fruit remains found in droppings. Researchers collected 222 droppings from two cave roosts monitored over three different seasons. Most seeds are excreted shortly after consumption due to a rapid gut transit time, but some seeds can remain in the gut for more than twelve hours. This heightens megabats' capacity to disperse seeds far from parent trees. As highly mobile frugivores, megabats have the capacity to restore forest between isolated forest fragments by dispersing tree seeds to deforested landscapes. This dispersal ability is limited to plants with small seeds that are less than in length, as seeds larger than this are not ingested. Predators and parasites , a flightless fly that parasitizes bats, including megabats Megabats, especially those living on islands, have few native predators. Non-native predators of flying foxes include domestic cats and rats. The mangrove monitor, which is a native predator for some megabat species but an introduced predator for others, opportunistically preys on megabats, as it is a capable tree climber. Another species, the brown tree snake, can seriously impact megabat populations; as a non-native predator in Guam, the snake consumes so many offspring that it reduced the recruitment of the population of the Mariana fruit bat (Pteropus mariannus) to essentially zero. The island is now considered a sink for the Mariana fruit bat, as its population there relies on bats immigrating from the nearby island of Rota to bolster it rather than successful reproduction. Predators that are naturally sympatric with megabats include reptiles such as crocodilians, snakes, and large lizards, as well as birds like falcons, hawks, and owls. During extreme heat events, megabats like the little red flying fox (Pteropus scapulatus) must cool off and rehydrate by drinking from waterways, making them susceptible to opportunistic depredation by freshwater crocodiles. Megabats are the hosts of several parasite taxa. Known parasites include Nycteribiidae and Streblidae species ("bat flies"), as well as mites of the genus Demodex. Blood parasites of the family Haemoproteidae and intestinal nematodes of Toxocaridae also affect megabat species. ==Range and habitat==

. Megabats are widely distributed in the tropics of the Old World, occurring throughout Africa, Asia, Australia, and throughout the islands of the Indian Ocean and Oceania. Outside of Southeast Asia, megabats have relatively low species richness in Asia. The Egyptian fruit bat is the only megabat whose range is mostly in the Palearctic realm; it and the straw-colored fruit bat are the only species found in the Middle East. The northernmost extent of the Egyptian fruit bat's range is the northeastern Mediterranean. Four megabat species, all Pteropus, are found on Japan, but none on its five main islands. In South Asia, megabat species richness ranges from two species in the Maldives to thirteen species in India. Megabat species richness in Southeast Asia is as few as five species in the small country of Singapore and seventy-six species in Indonesia. In Oceania, the countries of Palau and Tonga have the fewest megabat species, with one each. Papua New Guinea has the greatest number of species with thirty-six. Of the sixty-five species of Oceania, forest is a habitat for fifty-eight. Other habitat types include human-modified land (42 species), caves (9 species), savanna (5 species), shrubland (3 species), and rocky areas (3 species). ==Relationship to humans==

Food Megabats are killed and eaten as bushmeat throughout their range. Bats are consumed extensively throughout Asia, as well as in islands of the West Indian Ocean and the Pacific, where Pteropus species are heavily hunted. In continental Africa where no Pteropus species live, the straw-colored fruit bat, the region's largest megabat, is a preferred hunting target. In Guam, consumption of the Mariana fruit bat exposes locals to the neurotoxin beta-Methylamino-L-alanine (BMAA) which may later lead to neurodegenerative diseases. BMAA may become particularly biomagnified in humans who consume flying foxes; flying foxes are exposed to BMAA by eating cycad fruits. As disease reservoirs (Rousettus aegyptiacus), which has tested positive for Marburg virus and antibodies against the Ebola virus, though not the actual virus outbreaks overlaid on flying fox distribution map, with Nipah virus as blue icons and Hendra virus as red icons Megabats are the reservoirs of several viruses that can affect humans and cause disease. They can carry filoviruses, including the Ebola virus (EBOV) and Marburgvirus. where 31 people became ill and seven died. Species that have tested positive for the presence of EBOV include Franquet's epauletted fruit bat (Epomops franqueti), the hammer-headed fruit bat, and the little collared fruit bat. Additionally, antibodies against EBOV have been found in the straw-colored fruit bat, Gambian epauletted fruit bat (Epomophorus gambianus), Peters's dwarf epauletted fruit bat (Micropteropus pusillus), Veldkamp's dwarf epauletted fruit bat (Nanonycteris veldkampii), Leschenault's rousette, and the Egyptian fruit bat. Much of how humans contract the Ebola virus is unknown. Scientists hypothesize that humans initially become infected through contact with an infected animal such as a megabat or non-human primate. Megabats are presumed to be a natural reservoir of the Ebola virus, but this has not been firmly established. Microbats are also being investigated as the reservoir of the virus, with the greater long-fingered bat (Miniopterus inflatus) once found to harbor a fifth of the virus's genome (though not testing positive for the actual virus) in 2019. Due to the likely association between Ebola infection and "hunting, butchering and processing meat from infected animals", several West African countries banned bushmeat (including megabats) or issued warnings about it during the 2013–2016 epidemic; many bans have since been lifted. Other megabats implicated as disease reservoirs are primarily Pteropus species. Notably, flying foxes can transmit Australian bat lyssavirus, which, along with the rabies virus, causes rabies. Australian bat lyssavirus was first identified in 1996; it is very rarely transmitted to humans. Transmission occurs from the bite or scratch of an infected animal but can also occur from getting the infected animal's saliva in a mucous membrane or an open wound. Exposure to flying fox blood, urine, or feces cannot cause infections of Australian bat lyssavirus. Since 1994, there have been three records of people becoming infected with it in Queensland—each case was fatal. Flying foxes are also reservoirs of henipaviruses such as Hendra virus and Nipah virus. Hendra virus was first identified in 1994; it rarely occurs in humans. From 1994 to 2013, there have been seven reported cases of Hendra virus affecting people, four of which were fatal. The hypothesized primary route of human infection is via contact with horses that have come into contact with flying fox urine. There are no documented instances of direct transmission between flying foxes and humans. As of 2012, there is a vaccine available for horses to decrease the likelihood of infection and transmission. Nipah virus was first identified in 1998 in Malaysia. Since 1998, there have been several Nipah outbreaks in Malaysia, Singapore, India, and Bangladesh, resulting in over 100 casualties. A 2018 outbreak in Kerala, India, resulted in 19 humans becoming infected—17 died. The overall fatality rate is 40–75%. Humans can contract Nipah virus from direct contact with flying foxes or their fluids, through exposure to an intermediate host such as domestic pigs, or from contact with an infected person. A 2014 study of the Indian flying fox and Nipah virus found that while Nipah virus outbreaks are more likely in areas preferred by flying foxes, "the presence of bats in and of itself is not considered a risk factor for Nipah virus infection." Rather, the consumption of date palm sap is a significant route of transmission. The practice of date palm sap collection involves placing collecting pots at date palm trees. Indian flying foxes have been observed licking the sap as it flows into the pots, as well as defecating and urinating in proximity to the pots. In this way, humans who drink palm wine can be exposed to henipaviruses. The use of bamboo skirts on collecting pots lowers the risk of contamination from bat urine. Flying foxes can transmit several non-lethal diseases as well, such as Menangle virus and Nelson Bay virus. These viruses rarely affect humans, and few cases have been reported. In culture Megabats, particularly flying foxes, are featured in indigenous cultures and traditions. Folk stories from Australia and Papua New Guinea feature them. They were also included in Indigenous Australian cave art, as evinced by several surviving examples. Indigenous societies in Oceania used parts of flying foxes for functional and ceremonial weapons. In the Solomon Islands, people created barbs out of their bones for use in spears. Flying fox wings were depicted on the war shields of the Asmat people of Indonesia; they believed that the wings offered protection to their warriors. There are modern and historical references to flying fox byproducts used as currency. In New Caledonia, braided flying fox fur was once used as currency. On the island of Makira, which is part of the Solomon Islands, indigenous peoples still hunt flying foxes for their teeth as well as for bushmeat. The canine teeth are strung together on necklaces that are used as currency. Teeth of the insular flying fox (Pteropus tonganus) are particularly prized, as they are usually large enough to drill holes in. The Makira flying fox (Pteropus cognatus) is also hunted, despite its smaller teeth. Deterring people from using flying fox teeth as currency may be detrimental to the species, with Lavery and Fasi noting, "Species that provide an important cultural resource can be highly treasured." Emphasizing sustainable hunting of flying foxes to preserve cultural currency may be more effective than encouraging the abandonment of cultural currency. Even if flying foxes were no longer hunted for their teeth, they would still be killed for bushmeat; therefore, retaining their cultural value may encourage sustainable hunting practices. Lavery stated, "It's a positive, not a negative, that their teeth are so culturally valuable. The practice of hunting bats shouldn't necessarily be stopped, it needs to be managed sustainably." ==Conservation==

Status (Pteropus subniger), which was driven to extinction by overhunting As of 2019, the IUCN had evaluations for 187 megabat species. The status breakdown is as follows: • Extinct: 4 species (2.1%) • Critically endangered: 8 species (4.3%) • Endangered: 16 species (8.6%) • Vulnerable: 37 species (19.8%) • Near-threatened: 13 species (7.0%) • Least-concern: 89 species (47.6%) • Data deficient: 20 species (10.7%) Factors causing decline Anthropogenic sources Megabats are threatened by habitat destruction by humans. Deforestation of their habitats has resulted in the loss of critical roosting habitat. Deforestation also results in the loss of food resource, as native fruit-bearing trees are felled. Habitat loss and resulting urbanization leads to construction of new roadways, making megabat colonies easier to access for overharvesting. Additionally, habitat loss via deforestation compounds natural threats, as fragmented forests are more susceptible to damage from typhoon-force winds. while human persecution stemming from perceived damage to crops is also a large source of mortality. Some megabats have been documented to have a preference for native fruit trees over fruit crops, but deforestation can reduce their food supply, causing them to rely on fruit crops. Culling campaigns can dramatically reduce megabat populations. In Mauritius, over 40,000 Mauritian flying foxes were culled between 2014 and 2016, reducing the species' population by an estimated 45%. Megabats are also killed by electrocution. In one Australian orchard, it is estimated that over 21,000 bats were electrocuted to death in an eight-week period. Farmers construct electrified grids over their fruit trees to kill megabats before they can consume their crop. The grids are questionably effective at preventing crop loss, with one farmer who operated such a grid estimating they still lost of fruit to flying foxes in a year. Some electrocution deaths are also accidental, such as when bats fly into overhead power lines. Climate change causes flying fox mortality and is a source of concern for species persistence. Extreme heat waves in Australia have been responsible for the deaths of more than 30,000 flying foxes from 1994 to 2008. Females and young bats are most susceptible to extreme heat, which affects a population's ability to recover. Megabats are threatened by sea level rise associated with climate change, as several species are endemic to low-lying atolls. As many megabat species are located in the tectonically active Ring of Fire, they are also threatened by volcanic eruptions. Flying foxes, including the endangered Mariana fruit bat, have been nearly exterminated from the island of Anatahan following a series of eruptions beginning in 2003. == References ==