Megabats constitute the suborder Megachiroptera, 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. Fruit bats are restricted to the Old World in a tropical and subtropical distribution, ranging no further than the eastern Mediterranean and South Asia, and are absent from northwest Africa and southwest Australia.
Megabats, however contrary to their name, are not always large; the smallest species is 6 cm (2.4 in) long and thus smaller than some microbats. The largest attain a wingspan of 1.7 m (5.6 ft), weighing in at up to 1.6 kg (3.5 lb). Most fruit bats have large eyes, allowing them to orient themselves visually in twilight and inside caves and forests.
Megabats make up the only family (Pteropodidae) in order Chiroptera that is not capable of laryngeal echolocation, unlike the microbat. Echolocation and flight evolved early in the lineage of chiropterans and echolocation was later lost in family Pteropodidae. Both echolocation and flight are energetically expensive processes for bats. The nature of the flight and echolocation mechanism of bats allows for creation of echolocation pulses with minimal energy use. Energetic coupling of these two processes is thought to have allowed for both energetically expensive processes to evolve in bats. The loss of echolocation may be due to the uncoupling of flight and echolocation in megabats. The larger average body size of megabats compared to echolocating bats suggests that a larger body size disrupts the flight-echolocation coupling and made echolocation too energetically expensive to be conserved in megabats.
Behavior and ecology
Megabats mostly roost in trees and shrubs. Only those that possess echolocation venture into the dark recesses of caves. Because they eat fruit, some megabat species are unpopular with orchard owners. Megabats are frugivorous or nectarivorous, i.e., they eat fruits or lick nectar from flowers. Often, the fruits are crushed and only the juices are consumed. The teeth are adapted to bite through hard fruit skins. Large fruit bats must land to eat fruit, while the smaller species are able to hover with flapping wings in front of a flower or fruit.
Frugivorous bats aid the distribution of plants (and therefore forests) by carrying the fruits with them and spitting the seeds or eliminating them elsewhere. Nectarivores actually pollinate visited plants. They bear long tongues that are inserted deep into the flower; pollen passed to the bat is then transported to the next blossom visited, thereby pollinating it. This relationship between plants and bats is a form of mutualism known as chiropterophily. Examples of plants that benefit from this arrangement include the baobabs of the genus Adansonia and the sausage tree (Kigelia).
As disease reservoirs
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Fruit bats have been found to act as reservoirs for a number of diseases that are fatal to humans and domestic animals, but the bats themselves sometimes have no signs of infection.  A different species has emerged in Ivory Coast, another West African country, just east of Guinea and Liberia. According to a study, the virus in West Africa seems to have diverged from its lineage in Central Africa just within the past decade. It somehow leapfrogged over or around the Ivory Coast ebolavirus to situate itself in southeastern Guinea. That suggests the unnerving prospect that the Central African ebolavirus (the only one strictly known as Ebola virus) is expanding its range, either by infecting new populations of reservoir hosts or by migrations of those host animals.
Other viral diseases which can be carried by fruit bats include Australian bat lyssavirus and Henipavirus (notably Hendra virus and Nipah virus), both of which can prove fatal to humans. These bats have been shown to infect other species (specifically horses) with Hendra virus in Australian regions. Later, humans became infected with Hendra virus after being exposed to horse body fluids and excretions.
Fox Island, Australia, is believed to be home to the largest colony of flying foxes on the continent.
Bats are usually thought to belong to one of two monophyletic groups, a view that is reflected in their classification into two suborders (Megachiroptera and Microchiroptera). According to this hypothesis, all living megabats and microbats are descendants of a common ancestor species that was already capable of flight.
However, other views have been shared, and a vigorous debate persists to this date. For example, in the 1980s and 1990s, some researchers proposed (based primarily on the similarity of the visual pathways) that the Megachiroptera were in fact more closely affiliated with the primates than the Microchiroptera, with the two groups of bats having therefore evolved flight via convergence (see Flying primates theory). However, a recent flurry of genetic studies confirms the more longstanding notion that all bats are indeed members of the same clade, the Chiroptera. Other studies have recently suggested that certain families of microbats (possibly the horseshoe bats, mouse-tailed bats, and the false vampires) are evolutionarily closer to the fruit bats than to other microbats.
^ abNational Geographic, October 2007. "Deadly Contact," David Quammen, pp. 78–105.
^Researchers tested fruit bats for the presence of the Ebola virus between 2001 and 2003. Ebola virus is a zoonosis, an animal infection transmissible to humans. The animal in which a zoonosis lives its customary existence, discreetly, over the long term, and without causing symptoms, is called a reservoir host. The reservoir host of Ebola virus is still unknown, even after 38 years of efforts to identify it, since the original 1976 outbreak, although one or more kinds of fruit bats, including the hammer-headed bat, are suspects.
^Monson, C. S.; Banack, S. A.; Cox, P. A. (2003). "Conservation implications of Chamorro consumption of flying foxes as a possible cause of amyotrophic lateral sclerosis-parkinsonism dementia complex in Guam". Conservation Biology17 (3): 678–686. doi:10.1046/j.1523-1739.2003.02049.x.
^Pettigrew JD, Jamieson BG, Robson SK, Hall LS, McAnally KI, Cooper HM (1989). "Phylogenetic relations between microbats, megabats and primates (Mammalia: Chiroptera and Primates)". Philosophical Transactions of the Royal Society B325 (1229): 489–559. Bibcode:1989RSPTB.325..489P. doi:10.1098/rstb.1989.0102.