Pteropus
Pteropus is a genus of megabats which are among the largest bats in the world. They are commonly known as fruit bats or flying foxes, among other colloquial names.
They live in South Asia, Southeast Asia, Australia, East Africa, and some oceanic islands in the Indian and Pacific Oceans.
There are at least 60 extant species in the genus.
Flying foxes eat fruit and other plant matter, and occasionally consume insects as well. They locate resources with their keen sense of smell.
Most, but not all, are nocturnal. They navigate with keen eyesight, as they cannot echolocate.
They have long life spans and low reproductive outputs, with females of most species producing only one offspring per year. Their slow life history makes their populations vulnerable to threats such as overhunting, culling, and natural disasters. Six flying fox species have been made extinct in modern times by overhunting. Flying foxes are often persecuted for their real or perceived role in damaging crops. They are ecologically beneficial by assisting in the regeneration of forests via seed dispersal. They benefit ecosystems and human interests by pollinating plants.
Like other bats, flying foxes are relevant to humans as a source of disease, as they are the reservoirs of rare but fatal disease agents including Australian bat lyssavirus, which causes a rabies like illness, and Hendra virus; seven known human deaths have resulted from these two diseases. Nipah virus is also transmitted by flying foxes—it affects more people, with over 100 attributed fatalities. They have cultural significance to indigenous people, with appearances in traditional art, folklore, and weaponry. Their fur and teeth were used as currency in the past. Some cultures still use their teeth as currency today.
Taxonomy and etymology
The genus name Pteropus, from Ancient Greek 'πτερόν', meaning "wing", and 'πούς', meaning "foot", was coined by French zoologist Mathurin Jacques Brisson in 1762.Prior to 1998, genus authority was sometimes given to German naturalist Johann Christian Polycarp Erxleben. Although the Brisson publication predated the Erxleben publication, thus giving him preference under the Principle of Priority, some authors gave preference to Erxleben as genus authority because Brisson's publication did not consistently use binomial nomenclature. In 1998, the International Commission on Zoological Nomenclature decided that Brisson's 1762 publication was a "rejected work" for nomenclatural purposes. Despite rejecting the majority of the publication, the ICZN decided to conserve a dozen generic names from the work and retain Brisson as authority, including Pteropus.
The type species of the genus is the Mauritian flying fox, Pteropus niger.
The decision to designate P. niger as the type species was made by the ICZN through their plenary powers over biological nomenclature. The phrase "flying fox" has been used to refer to Pteropus bats since at least 1759.
Species
Description
External characteristics
Flying fox species vary in body weight, ranging from. Across all species, males are usually larger than females.The large flying fox has the longest forearm length and reported wingspan of any bat species, but some bat species exceed it in weight.
Its wingspan is up to, and it can weigh up to. The Indian and great flying foxes are heavier, at, respectively.
Outside this genus, the giant golden-crowned flying fox is the only bat with similar dimensions.
Most flying fox species are considerably smaller and generally weigh less than.
Smaller species such as the masked, Temminck's, Guam, and dwarf flying foxes all weigh less than.
The pelage is long and silky with a dense underfur. In many species, individuals have a "mantle" of contrasting fur color on the back of their head, the shoulders, and the upper back. They lack tails. As the common name "flying fox" suggests, their heads resemble that of a small fox because of their small ears and large eyes. Females have one pair of mammae located in the chest region. Their ears are long and pointed at the tip and lack tragi, the outer margin of each ear forming an unbroken ring. The toes have sharp, curved claws. While microbats only have a claw on each thumb of their forelimbs, flying foxes additionally have a claw on each index finger.
Skull and dentition
The skulls of Pteropus species are composed of 24 bones, the snout is made of 7, the cranium of 16 and the mandible is a single bone. It has a large and bulbous braincase. Like all mammals, flying foxes have three middle ear ossicles which assist in transmitting sound to the brain. Flying fox skulls continue to develop after they are born. Compared to adults, young flying foxes have very short snouts; as they reach maturity, the maxilla elongates, gaining bone between the zygomatic processes and the canine teeth.Based on the grey-headed flying fox's development, pups are born with some milk teeth already erupted: canines and incisors. By 9 days old, all the milk teeth have emerged, with a dental formula of and a total of 20 teeth. By 140 days old, all the milk teeth have fallen and been replaced by permanent teeth. The canines are usually replaced first, followed by the premolars, incisors, and then molars. The adult dental formula is for a total of 34 teeth. The occlusal surface of the molars is generally smooth but with longitudinal furrows.
Internal systems
Flying foxes have large hearts and a relatively fast heart rate: resting individuals have a heart rate of 100–400 beats per minute.Flying foxes have simple digestive tracts; the time between ingestion and excretion is as short as 12 minutes. They lack both a cecum and an appendix. The stomach has marked cardiac and fundic regions.
Intelligence
The megabats, including flying foxes, have the greatest encephalization quotient of any bat family at 1.20.This value is equivalent to that of domestic dogs. Flying foxes display behaviors that indicate a reliance on long-term information storage. Though they have wide-ranging movements and cover thousands of square kilometers annually, they are consistently able to locate the same resource patches and roosts. They will visit these resource patches consistently in a strategy known as trap-lining. They can also be conditioned to perform behaviors, such as one study where spectacled flying foxes were trained to pull a lever using juice as a reinforcement. In a follow-up to the initial study, individuals who had learned to pull the lever to receive juice still did so 3.5 years later.
Senses
Smell
Flying foxes rely heavily on their sense of smell.They have large olfactory bulbs to process scents. They use scent to locate food, for mothers to locate their pups, and for mates to locate each other. Males have enlarged androgen-sensitive sebaceous glands on their shoulders that 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 identified from the glands of four species, no compound was found in all species. Males also engage in "urine washing", meaning that they coat themselves in their own urine.
Sight
Flying foxes do not echolocate, and therefore rely on sight to navigate. Their eyes are relatively large and positioned on the front of their heads, giving them binocular vision.Like most mammals, though not primates, they are dichromatic. They have both rods and cones; they have "blue" cones that detect short-wavelength light and "green" cones that detect medium-to-long-wavelengths. The rods greatly outnumber the cones, however, as cones comprise only 0.5% of photoreceptors. Flying foxes are adapted to seeing in low-light conditions.
Evolutionary history
Flying foxes are poorly represented in the fossil record. Relative to the current number of extant species, the Pteropodidae has one of the most incomplete fossil records of any bat group. As of 2014, no flying fox fossils are known from before the Holocene.Many flying foxes live in the tropics, where conditions for fossilization are poor. Based on molecular evolution, flying foxes diverged from a common ancestor with Rousettus 28-18 million years ago and from their sister taxa Neopteryx and Acerodon 6.6-10.6 million years ago. Neopteryx, Acerodon, Desmalopex, Melonycteris, Mirimiri, Pteralopex, and Styloctenium are all relatively closely related to the flying foxes, as they are the other members of its subfamily Pteropodinae.
Phylogenetic analysis indicates that flying foxes diversified rapidly in an explosive evolutionary radiation, creating many taxa in a relatively short time frame. Most flying fox lineages emerged after the Zanclean, with two major clades created: one consisting of the Indian Ocean species and the other of the Melanesian, Micronesian, Australian, and insular Southeast Asian species. Flying foxes likely originated on mainland Asia; molecular data suggests that there were at least three colonization events into the Indian Ocean. One event resulted in Livingstone's fruit bat and the Pemba flying fox, which are the westernmost flying foxes. A second colonization event resulted in the Rodrigues flying fox to Rodrigues Island; while a third event resulted in several species diverging to Mauritius, the Seychelles, Madagascar, and Aldabra.
With one possible exception - the masked flying fox, flying foxes are likely monophyletic. There are over 60 extant species of flying fox. Flying foxes are now present from the western Indian Ocean midway through the Pacific Ocean as far east as the Cook Islands. They are found in tropical and subtropical climates.