PteropodidaeOld World fruit bats(Also: flying foxes)

Diversity

Members of Pteropodidae are known colloquially as the flying foxes, or Old World fruit bats. The family is composed of 41 genera and about 170 species. The most species-rich genus in the family is Pteropus with 59 species, many of which are island endemics. Body and wing size ranges from small (37 mm forearm length) to large (220 mm forearm length). The family boasts the largest bats in the world. Pteropus vampyrus individuals have a wingspan of up to 1.7 m. Pteropus giganteus individuals have a comparable wingspan but a greater mass, with males weighing between 1.3 and 1.6 kg. Pteropodids are strictly vegetarian, foraging for fruits, nectar, and pollen using their sight and a sensitive olfactory system. Bats of the genus Rousettus use tongue clicks as a crude form of echolocation while navigating in the dark. Some species are migratory, covering vast distances, while others have more moderate home ranges. Eidolon helvum individuals aggregate in numbers reaching the hundreds of thousands, yet many species roost with only a few conspecifics. Members of Pteropodidae service the ecosystems they inhabit by playing important roles as pollinators and seed dispersers. (Fenton, 2001; Koopman, 1994; Neuweiler, 2000; Nowak, 1999)

Geographic Range

Pteropodidae has a tropical and subtropical distribution in the Old World (eastern hemisphere). Species are found as far north as the eastern Mediterranean, continuing along the southern coast of the Arabian Peninsula and across South Asia. Species are found as far south as South Africa, the islands of the Indian Ocean, and to the northern and western coasts of Australia. The longitudinal range reaches from the Atlantic coast of Africa to the islands of the western Pacific. Pteropodids are absent from northwest Africa, southwest Australia, a majority of the Palearctic region, and all of the Western Hemisphere. (Koopman, 1994; Mickleburgh, et al., 1992; Nowak, 1994)

Habitat

Pteropodids typically occur in primary or maturing secondary forests. A few species inhabit savannah habitats where they roost in bushes and low trees. Over half of the 41 genera are made up of species that roost in trees. Gregarious species roost on the open branches of large, canopy-emergent trees. Pteropodids that roost singly or in small groups can be found in dead palm leaves, aerial roots, and even arboreal termite nests. These bats also tend to have cryptic coloration and wrap themselves with their wings in order to resemble dead leaves. In one species, Cynopterus sphinx, individuals construct tents by chewing folds in palm leaves. Caves, cliff walls, mines, and the eaves of buildings also serve as roosting locations for species in 17 genera. Most cave-dwelling species are limited to the lit areas near the opening, while members of the genus Rousettus are able to navigate the darker regions using crude echolocation. (Mickleburgh, et al., 1992; Nowak, 1994)

Flowering plants are essential to the diet of pteropodid species; therefore, flying foxes mostly use woodlands or orchards for food. Canopy emergent fruiting trees, such as fig and baobab trees, are frequently used as a food source. The flowers of baobab trees have a strong fragrance and are located on the crown of the tree, which makes them easily accessible to bats (a flower syndrome known as chiropterophily). Many pteropodid species are found in coastal areas and drink salt water in order to supplement nutrients lacking in their diet. (Fenton, 2001)

A few species are migratory. Eidolon helvum individuals gather in large numbers and migrate hundreds of kilometers northward with seasonal rains, only to return to southern Africa at the end of the rainy season. Pteropus scapulatus populations make major, and somewhat erratic movements within Australia, following the flowering periods of Eucalyptus trees. Many species of Pteropus roost on islands and make daily migrations to the mainland for foraging. Some species range from sea level to 2500 m, yet little is known about any significant elevational migrations. (Fenton, 2001; Mickleburgh, et al., 1992; Nowak, 1994)

Physical Description

The head and body length of pteropodids varies from 50 mm to 406 mm. Despite size, many characteristics are shared among genera. A relatively long rostrum (pronounced in nectarivores), large eyes, and simple external ears give members of this family a dog or fox-like appearance (hence “flying fox”). The genera Nyctimene and Paranyctimene are exceptions in that they contain tubular nostrils that project from the upper surface of the snout. On the skull, postorbital processes are present over the orbital region. The palatine extends posterior to nearly cover the presphenoid. No more than two upper and two lower incisors are present in adults, otherwise cheek and canine dentition varies between species. The tongue is highly protrusible in nectar feeding bats and often complex with terminal papillae. (Myers, 2001; Neuweiler, 2000; Nowak, 1999)

The chest is robust, comprised of the down-thrusting pectoralis and serratus muscles. The articulating regions of the humerus never come into contact with the scapula, which differs from a locking mechanism that occurs in the shoulder joint of other bat groups. The second digit is relatively independent from the third digit and contains a vestigial claw that adorns the leading edge of the wing. (Altringham, 1996; Neuweiler, 2000)

Modifications for hanging include a relocation of the hip socket. The acetabulum is shifted upward and dorsally, and articulates with a large headed femur for a wider range of motion. In contrast to most other mammal orders, the legs cannot be positioned in a straight line under the body. In conjunction with large claws on their feet, pteropodids use a tendon-ratchet system that allows them to hang without prolonged muscular contraction. The legs manipulate a primitive uropatagium during flight. Aside from Notopteris, most species are tailless or with just a spicule of a tail. (Neuweiler, 2000)

Several species of Pteropodidae demonstrate sexual dimorphism. Males of Hypsignathus monstrosus have rather outlandish facial features, while females have the conservative fox-like look. Males of the genus Epomops have distinctive white patches in association with a glandular membrane on their shoulders, whereas females do not. Considering the whole family, males are generally larger than females. The penis of all pteropodids is a pendant and freely movable organ, resembling that of Primates. Juveniles are typically naked or have a velvety coat that is darker than adult pelage. (Neuweiler, 2000; Nowak, 1999)

  • Sexual Dimorphism
  • sexes alike
  • male larger
  • sexes colored or patterned differently
  • ornamentation

Reproduction

Mating behavior in pteropodids is highly variable, and much is unknown. The males of one genus (Hypsignathus) set up lekking territories twice a year and draw in females with unique vocalizations and wing-flapping displays. Male epauletted fruit bats (genus Epomophorus) often display their concealed epaulets (hair tufts near the shoulder) and emit courting calls to attract females. Many species form harems consisting of 1 dominant male and up to 37 females, while bachelor males roost separately. (Nowak, 1999; Storz, et al., 2000)

While most bats have one reproduction event per year, many pteropodids are polyestrous, with two seasonal cycles corresponding to the annual wet and dry seasons. Usually one young is born per pregnancy, but twins are not uncommon. Upon fertilization, ova implantation in the uteri can be immediate or delayed, probably in response to the environment. Development of the embryo (once implanted) may also be delayed, probably to ensure birth at a time when fruit is available during the rainy seasons. One species, Macroglossus minimus, exhibits asynchronous breeding and sperm storage, suggesting the importance of birth during an optimal (rainy) season. (Hood and Smith, 1989; Nowak, 1999)

Pregnant females usually leave social roosts to form nursery groups with other pregnant females. Females in nursery roosts form their own social network and take care of each other through mutual grooming. Gestation periods usually lasts 4 to 6 months, but can be longer if implantation is delayed. Birth patterns of pteropodids have been widely studied and usually occur during the wet periods both in the northern latitudes (February to April) and the southern latitudes (August to November). Species that are polyestrous will give birth during both of these rainy seasons. It is predicted that birth during these seasons yields high survival rates because lactation occurs when fruit availability is at a maximum. Birth is followed by postpartum estrous and subsequent mating. After weaning, young may stay with their mothers up to 4 months. Sexual maturity in juveniles is reached by 2 years old or earlier. Female sexual maturity is reached earlier than in males. (Kofron, 2007; Kretschmann and Hayes, 2004; Nowak, 1999)

Female pteropodids are primarily responsible for rearing the young. Lactation lasts anywhere from 7 weeks to 4 months, and the mother may care for her young slightly longer. In one genus (Dyacopterus), males with functional mammary glands have been reported lactating, which suggests the sharing of juvenile care among both parents. (Nowak, 1999)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female

Lifespan/Longevity

Pteropodids have been known to live at least 30 years, both in captivity and in the wild. (Nowak, 1999)

Behavior

Pteropodids are different from all other chiropteran in that, with the exception of Rousettus species, they do not echolocate. Pteropodids rely instead on vision and olfaction to perceive their world. Pteropodids can functionally be divided into two groups based on size. Smaller pteropodids such as Micropteropus pusilla, Epomops buttikorteri, and Epomophorus wahlbergi tend to have shorter, deeper wings which allow for more maneuverable flight under the canopy. Larger pteropodids such as Eidolon, Pteropus, and Acerodon species have longer, narrower wings which allow for efficient long distant flight. Pteropodid species display varying degrees of coloniality. This range is broad, from solitary species to those that roost in groups of up to 200,000 individuals. Roost size may also vary seasonally within a species, possibly due to a depletion of local food sources. Some species commonly roost in mixed groups with other species. Roost selection by pteropodids is poorly understood. Pteropodids roost in a wide range of habitats, from cultivated kapok plantations to rainforests and mangroves. Some species are associated with particular types of plants. Pteropodids can show long term fidelity to roost sites when the sites are undisturbed. Some species of Pteropus in Australia have been recorded using the same roost for over 80 years. (Kunz and Fenton, 2003; Mickleburgh, et al., 1992)

Communication and Perception

Pteropodids rely heavily on vision and olfaction when navigating and foraging. Intraspecific communication is often vocal. In some species, such as Pteropus poliocephalus, vocal signaling may be associated with specific motor activities which enhance the meaning of the vocal signal. In species such as Eidolon helvum, sexually dimorphic sebaceous glands which are larger in males may provide olfactory behavioral cues. (Mainoya and Howell, 1979; Van Parijs and Corkeron, 2002)

Food Habits

Pteropodids are frugivorous and nectarivorous. Some species also eat flowers of the plants they visit. Foraging habits are not well documented, though many species of the genus Pteropus rely heavily on figs. Many species rely on broad array of resources, though there may be a functional dichotomy between large species that rely heavily on canopy resources and smaller species that can use understory resources. Some larger species can use the claws on their thumbs and second digits to climb into the understory and seek out fruit that is hidden or inaccessible by flight. (Kunz and Fenton, 2003; Mickleburgh, et al., 1992)

Predation

Birds of prey and carnivorous mammals, as well as snakes and large lizards may prey on pteropodids. Pteropodids tend to have fewer predators on islands. However, there have been several cases of introductions of non-native, arboreal snakes which have decimated pteropodid populations. (Mickleburgh, et al., 1992)

Ecosystem Roles

Pteropodids provide important pollination and seed dispersal services to a wide range of plants. On islands in the south Pacific, pteropodids are the principle pollinators and dispersers of plants. Many plants have adaptations specifically for seed dispersal and pollination by bats, such as fruiting or flowering at the ends of branches and at bat accessible locations in the canopy. Eidolon dupreanum has been shown to likely be the sole pollinator of the baobab tree Adansonia suarezensis in Madagascar. (Cox, et al., 2005; Kunz and Fenton, 2003; Mickleburgh, et al., 1992; Andriafidison, et al., 2006)

  • Ecosystem Impact
  • disperses seeds
  • pollinates

Economic Importance for Humans: Positive

Larger species of pteropodids are hunted for their meat. Both subsistence and commercial hunting of Pteropus species have been reported. Consumer demand for Pteropus species on the island of Guam has been so great that it has resulted in the extinction of at least one species in the Pacific region. Flying foxes are also important in the dispersal and pollination of economically important plants. They attract tourists in some areas and produce accumulations of guano that can be used as fertilizer. (Mickleburgh, et al., 1992)

  • Positive Impacts
  • food
  • ecotourism
  • produces fertilizer
  • pollinates crops

Economic Importance for Humans: Negative

Many crop species are attractive food sources for pteropodids. Because cultivars are often developed from wild species, these commercial crops have the same characteristics that wild plants evolved to attract bats to their fruit. Fruit growers have experimented with visual, audio, and olfactory deterrents as well as electric wire to keep pteropodids from eating their crops. Pteropodids may also be dispersers of invasive plant species, as they consume crops introduced for cultivation and may disperse the seeds into natural habitat. Pteropodids have been indicated as reservoirs for a variety of viruses such as Ebola and other viruses in the family Paramyxoviridae. Hendra virus, Menangle virus, and Nipah virus have all been linked to pteropodids. (Mickleburgh, et al., 1992)

  • Negative Impacts
  • injures humans
    • carries human disease
  • crop pest

Conservation Status

Many factors threaten pteropodids throughout their range. Human activities have decimated populations of certain species directly through hunting or indirectly through habitat destruction. In Asia and Australia, deforestation is the most important contributor to pteropodid population decline. Some species are vulnerable to typhoons and hurricanes which may destroy roosting habitat on islands. The IUCN Red List of Threatened Species lists 5 species as recently extinct, 10 species as critically endangered, 19 species as endangered, 15 species as near threatened, and 39 species as vulnerable, suggesting that nearly half of all pteropodid species face significant threats to population viability. (IUCN 2008, 2008; Kunz and Fenton, 2003)

  • IUCN Red List [Link]
    Not Evaluated

Contributors

Tanya Dewey (), Animal Diversity Web, Kenneth Cody Luzynski (author), University of Michigan-Ann Arbor, Emily Margaret Sluzas (author), University of Michigan-Ann Arbor, Megan Marie Wallen (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

World Map

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

arboreal

Referring to an animal that lives in trees; tree-climbing.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

crepuscular

active at dawn and dusk

delayed implantation

in mammals, a condition in which a fertilized egg reaches the uterus but delays its implantation in the uterine lining, sometimes for several months.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

food

A substance that provides both nutrients and energy to a living thing.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

frugivore

an animal that mainly eats fruit

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

migratory

makes seasonal movements between breeding and wintering grounds

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nectarivore

an animal that mainly eats nectar from flowers

nocturnal

active during the night

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

polygynous

having more than one female as a mate at one time

rainforest

rainforests, both temperate and tropical, are dominated by trees often forming a closed canopy with little light reaching the ground. Epiphytes and climbing plants are also abundant. Precipitation is typically not limiting, but may be somewhat seasonal.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

social

associates with others of its species; forms social groups.

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5? N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

ultrasound

uses sound above the range of human hearing for either navigation or communication or both

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

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Andriafidison, D., R. Andrianaivoarivelo, O. Ramillijaona, M. Razanahoera, J. MacKinnon, R. Jenkins, P. Racey. 2006. Nectarivory by endemic malagasy fruit bats during the dry season. Biotropica, 38/1: 85-90.

Cox, P., T. Elmquist, E. Pierson, W. Rainey. 2005. Flying Foxes as Strong Interactors in South Pacific Island Ecosystems: A Conservation Hypothesis. Conservation Biology, 5/4: 448-454.

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