Fruit bats

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 (now recognized as a synonym of Dobsonia). Gray's spelling was possibly based on a misunderstanding of the suffix of "Pteropus". "Pteropus" comes from Ancient Greek pterón meaning "wing" and poús 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.

In 1875, the zoologist George Edward Dobson was the first to split the order Chiroptera (bats) into two suborders: Megachiroptera (sometimes listed as Macrochiroptera) and Microchiroptera, which are commonly abbreviated to megabats and microbats. 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.

A 2001 study found that the dichotomy of megabats and microbats did not accurately reflect their evolutionary relationships. Instead of Megachiroptera and Microchiroptera, the study's authors proposed the new suborders Yinpterochiroptera and Yangochiroptera. This classification scheme has been verified several times subsequently and remains widely supported as of 2019. Since 2005, this suborder has alternatively been called "Pteropodiformes". Yinpterochiroptera contained species formerly included in Megachiroptera (all of Pteropodidae), as well as several families formerly included in Microchiroptera: Megadermatidae, Rhinolophidae, Nycteridae, Craseonycteridae, and Rhinopomatidae. 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. …

Megabats take their name from their larger weight and size; the largest, the great flying fox (Pteropus neohibernicus), weighs up to 1.6 kg (3.5 lb); some members of Acerodon and Pteropus have wingspans reaching up to 1.7 m (5.6 ft). Despite the fact that body size was a defining characteristic that Dobson used to separate microbats and megabats, not all species of megabat are larger than microbats; the spotted-winged fruit bat (Balionycteris maculata), a megabat, weighs only 14.2 g (0.50 oz). 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. A 2004 review stated that 28% of megabat species weigh less than 50 g (1.8 oz).

Megabats can be distinguished from microbats in appearance by their dog-like faces, by the presence of claws on the second digit , and by their simple ears. 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. A 2011 study of 167 megabat species found that while the majority (63%) have fur that is a uniform color, other patterns are seen in this family. These include countershading in four percent of species, a neck band or mantle in five percent of species, stripes in ten percent of species, and spots in nineteen percent of species.

Unlike microbats, megabats have a greatly reduced uropatagium, which is an expanse of flight membrane that runs between the hind limbs. Additionally, the tail is absent or greatly reduced, with the exception of Notopteris species, which have a long tail. 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.

Megabats have large orbits, which are bordered by well-developed postorbital processes posteriorly. The postorbital processes sometimes join to form the postorbital bar. The snout is simple in appearance and not highly modified, as is seen in other bat families. The length of the snout varies among genera. …

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.

With very few exceptions, megabats do not echolocate, and therefore rely on sight and smell to navigate. They have large eyes positioned at the front of their heads. These are larger than those of the common ancestor of all bats, with one study suggesting a trend of increasing eye size among pteropodids. A study that examined the eyes of 18 megabat species determined that the common blossom bat (Syconycteris australis) had the smallest eyes at a diameter of 5.03 mm (0.198 in), while the largest eyes were those of large flying fox (Pteropus vampyrus) at 12.34 mm (0.486 in) in diameter. 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. All species examined had retinae with both rod cells and cone cells, but only the Pteropus species had S-cones, which detect the shortest wavelengths of light; because the spectral tuning of the opsins was not discernible, it is unclear whether the S-cones of Pteropus species detect blue or ultraviolet light. Pteropus bats are dichromatic, possessing two kinds of cone cells. The other three genera, with their lack of S-cones, are monochromatic, unable to see color. …

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. As of 2013, fourteen genera of megabat are present in Africa, representing twenty-eight species. Of those twenty-eight species, twenty-four are only found in tropical or subtropical climates. The remaining four species are mostly found in the tropics, but their ranges also encompass temperate climates. In respect to habitat types, eight are exclusively or mostly found in forested habitat; nine are found in both forests and savannas; nine are found exclusively or mostly in savannas; and two are found on islands. Only one African species, the long-haired rousette (Rousettus lanosus), is found mostly in montane ecosystems, but an additional thirteen species' ranges extend into montane habitat.

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. In East Asia, megabats are found only in China and Japan. In China, only six species of megabat are considered resident, while another seven are present marginally (at the edge of their ranges), questionably (due to possible misidentification), or as accidental migrants. 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. Of the ninety-eight species of megabat found in Asia, forest is a habitat for ninety-five of them. Other habitat types include human-modified land (66 species), caves (23 species), savanna (7 species), shrubland (4 species), rocky areas (3 species), grassland (2 species), and desert (1 species).

In Australia, five genera and eight species of megabat are present. These genera are Pteropus, Syconycteris, Dobsonia, Nyctimene, and Macroglossus. …

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.

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. The presence of Marburgvirus, which causes Marburg virus disease, has been confirmed in one species, the Egyptian fruit bat. The disease is rare, but the fatality rate of an outbreak can reach up to 88%. The virus was first recognized after simultaneous outbreaks in the German cities of Marburg and Frankfurt as well as Belgrade, Serbia, in 1967, where 31 people became ill and seven died. The outbreak was traced to laboratory work with vervet monkeys from Uganda. The virus can pass from a bat host to a human (who has usually spent a prolonged period in a mine or cave where Egyptian fruit bats live); from there, it can spread person-to-person through contact with infected bodily fluids, including blood and semen. The United States Centers for Disease Control and Prevention lists a total of 601 confirmed cases of Marburg virus disease from 1967 to 2014, of which 373 people died (62% overall mortality).

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. …