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Pteropus poliocephalusgray-headed flying fox

By Christina DeHaven

Geographic Range

Pteropus poliocephalus is endemic to the eastern coast of Australia. These bats can be found from Bundaberg and Mayborough in Queensland to Melbourne in Victoria. The previous range has shifted southward by approximately 750 km, possibly due to a change in climate. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Parry-Jones and Augee, 2001; Tidemann and Nelson, 2004)

Habitat

Pteropus poliocephalus is found in a variety of habitats including rainforests, woodlands, and swamps located in Eastern Australia. They are typically found at elevations less than 200 m, but have been found at elevations as great as 700 m. These bats prefer to roost in the branches of large trees. They are usually not found more than 150 km inland and are even present on some secluded islands. Because of encroachment of human activity into their habitats, they are sometimes found in suburban areas, using the agricultural lands of their human neighbors as a food source. Pteropus poliocephalus is a semi-migratory species. The migrations of these animals have been attributed to different reasons. They often go where the food supply is abundant, although it has been hypothesized that they also undertake these long-distance flights to enhance their mating opportunities, or to gather more information about other parts of their range. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Menkhorst, 1995; Parry-Jones and Augee, 2001; Richards, 1984; Tidemann and Nelson, 2004)

  • Range elevation
    700 (high) m
    2296.59 (high) ft

Physical Description

Pteropus poliocephalus is the largest bat in Australia. As with all members of Pteropodidae, P. poliocephalus does not have a tail, and claws are present on the first and second digits. They do not echolocate, and therefore, the distinctive enlarged tragus or leaf-ornamentation found in most species of Microchiroptera is not present. Since they do not echolocate, they must rely on their large eyes for navigation and finding food. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Feldhamer, et al., 2004; Menkhorst, 2001; Richards, 1984; Taylor, 1984)

As the species' common name implies, grey-headed flying-foxes have faces which are fox-like. The body is dark grey, with the fur on the head being of a lighter color grey. There is also a reddish-brown collar of fur that encircles the neck. Fur on the legs extends all the way to the ankle, which is one distinguishing characteristic from other members of the genus Pteropus. The patagium is black, and it is possible for the wingspan of some individuals to be up to one meter. The head and body length is between 230 and 289 mm, with an average of 253 mm. The forearm length is between 138 and 180 mm, with an average of 161 mm. Weight generally varies between 600 and 1000 g, with an average of 677 g. However, some individuals have been recorded as weighing more than 1 kg. These figures are somewhat different according to different sources, but they are generally within a few units of each other. These bats have a basal metabolic rate of approximately 3.162 cm^3 oxygen/h. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Kunz and Stern, 1995; McNab and Bonaccorso, 1995; Richards, 1984)

  • Sexual Dimorphism
  • male larger
  • Range mass
    600 to 1000 g
    21.15 to 35.24 oz
  • Average mass
    677 g
    23.86 oz
  • Range length
    230 to 289 mm
    9.06 to 11.38 in
  • Average length
    253 mm
    9.96 in
  • Average wingspan
    1 m
    3.28 ft
  • Average basal metabolic rate
    316.2 cm3.O2/g/hr
  • Average basal metabolic rate
    1.768 W
    AnAge

Reproduction

During the nursing period, males and females form monogamous mating-pairs. Males utilize strong-smelling secretions from their scapular glands (located on the shoulder) and loud calls in order to establish territories and ward off unwanted males. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Richards, 1984)

Grey-headed flying foxes mate annually between April and May, with males reaching reproductive maturity at approximately 30 months of age. Mating has been observed throughout the year; however, males are only fertile during the mating period. Females that are close to giving birth segregate from the males. Mothers give birth to a single young between October and November, after a 6-month gestation period. Twins are extremely rare and do not usually survive in the wild. Weaning occurs between 5 and 6 months of age, and offspring are independent after about 6 months. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Menkhorst, 1995; Richards, 1984; Tidemann and Nelson, 2004; Webb and Tidemann, 1996)

  • Breeding interval
    Grey-headed flying-foxes breed once yearly.
  • Breeding season
    Breeding occurs from April to May
  • Range number of offspring
    1 to 2 (rare)
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Average gestation period
    6 months
  • Range weaning age
    5 (low) months
  • Average weaning age
    6 months
  • Average time to independence
    6 months
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    540 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    30 months
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    540 days
    AnAge

When born, the young weigh between 46 and 92 grams and are somewhat altricial, as they cannot fly and have no fur on the underside. Female P. poliocephalus carry their young, which cling to the fur on the mother's belly, for the first 4 to 5 weeks after birth. Females carry their young even while foraging. For the next 12 weeks or so, the young are left at the nesting site at night while the mother forages. At about 3 months of age the young are independent enough to forage on their own; however, they are not completely weaned until about 6 months of age. This extended period of nursing is due to the fact that bats provide their young with milk until they have at least 90% of their adult wingspan and at least 70% of their adult body mass, because the young cannot achieve sustained flight until they have reached these dimensions. Females have been known to abandon their young in times of food shortages. (Kunz and Stern, 1995; Menkhorst, 1995; Nowak, 1999; Tidemann, 1995)

Although males do not directly care for the young, they do mark and defend territories for their families during the period of nursing. Thus, they play some role in protecting the young.

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

Lifespan/Longevity

Grey-headed flying-foxes generally live for a long period of time, with the average reproductively active adult being between 6 and 10 years old. Two individuals are reported to have been 15 years old. However, the expected lifespan of wild individuals ranges from 21.6 to 59.2 months. Lifespan is affected mostly by food availability and negative human interactions, such as deforestation and culling. In captivity, where food availability is not an issue for survival, these bats have a much longer lifespan. (NSW Scientific Committee, 2001; Tidemann and Nelson, 2004)

  • Range lifespan
    Status: wild
    21.6 to 180 months
  • Average lifespan
    Status: wild
    40.4 months
  • Typical lifespan
    Status: wild
    21.6 to 59.2 months
  • Average lifespan
    Status: wild
    40.4 months
  • Average lifespan
    Status: captivity
    23.6 years
    AnAge

Behavior

As with many species of bats, P. poliocephalus is a very social animal, with a very complex social arrangement. Feeding occurs at night, and they roost during the day. They congregate in large numbers, up to several thousand animals, especially during times of mating. Territorial activity occurs mainly during the nursing period, when a male marks the territory and both he and his mate defend it. The territory usually consists of a length of a branch and little more. Also during the nursing period, family units are formed, with non-breeding bats living on the periphery of the group. Males sometimes exhibit philopatry, which is returning to their birth site in order to breed. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Richards, 1984; Tidemann and Nelson, 2004; Tidemann, 1995)

Congregations are termed camps and are often formed in gullies. These gullies are usually close to a water source and in dense canopies of vegetation. These camps are faithfully returned to year after year, making them a traditional home for P. poliocephalus. This is a highly mobile species, in that individuals will often fly several kilometers away from camp in order to find food. These bats migrate with the seasons, which influence the amount and kinds of food present around a particular camp. However, it seems that the abundance of food is the driving force, and it is not unusual for camps to be occupied during seasons when they are normally abandoned. (Parry-Jones and Augee, 2001; Tidemann and Nelson, 2004)

Home Range

The exact home range size for these bats has not been reported. Individuals may fly several kilometers from a camp in order to forage. (Parry-Jones and Augee, 2001; Tidemann and Nelson, 2004; Parry-Jones and Augee, 2001; Tidemann and Nelson, 2004)

Communication and Perception

What P. poliocephalus lacks in echolocation, it has made up for with a sophisticated array of vocalizations, which are comprised of a series of complicated squeaks and squeals. There are more than 20 different calls which these bats use in communicating with each other, and because they form large groups, roosting sites can be quite noisy.

Because they do not echolocate, they rely heavily on vision and olfaction in perceiving their environment. Their large eyes help them in navigating through their habitat. Males are known to use a strongly scented secretion in marking territory, and females are able to find their young by scent. Olfaction is also used in locating food items. Although not specifically reported, it is likely that there is important tactile communication between mothers and their young as well as between mates. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Menkhorst, 2001; Richards, 1984; Taylor, 1984)

Food Habits

Foraging occurs at night, and it is not unusual for individuals to fly up to 50 km away from their campsites, although most tend to stay within 15 km. These bats tend to forage in forest canopies, open forests, rainforests, and even swamps; however, they sometimes visit cultivated gardens and fruit crops in search of food. When eating, the bats bite pieces off of their food, and then chew it vigorously, spitting out portions that are not swallowed. Different foods are eaten at different times of the year, depending on availability. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Parry-Jones and Augee, 2001; Tidemann and Nelson, 2004; Tidemann, 1995)

The diet of P. poliocephalus includes fruits, pollen, nectar, and bark. Their preferred food source is eucalyptus blossom, of which Eucalyptus gummifera, Eucalyptus muellerana, Eucalyptus globoidea and Eucalyptus botryoides are most often consumed. The main sources utilized for pollen consumption belong in the families Myrtaceae and Proteaceae, although pollens from other families are consumed when present. One of their favorite fruits is fig (Ficus); however, these bats have been known to consume stone fruits (e.g. peach, plum, nectarine). Occasionally they also consume the leaves of poplar (g. Populus) and grey mangrove (Avicennia marina). Other food items that have been found in fecal matter include fruits from Phoenix canariensis, Ligustrum and Solanum mauritianum, among many others. (Menkhorst, 1995; Parry-Jones and Augee, 2001)

  • Plant Foods
  • leaves
  • wood, bark, or stems
  • fruit
  • nectar
  • pollen
  • flowers

Predation

Other Pteropus species are known to be preyed upon by snakes, such as brown tree snakes (Boiga irregularis). However, beyond reports of humans killing these animals, information pertaining to specific predators of P. poliocephalus was not found. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Nowak, 1999; NSW Scientific Committee, 2001)

Ecosystem Roles

Many different fruits and pollens are consumed by P. poliocephalus, making this species highly important in seed dispersal and pollination of plants. Certain plants enjoy a wider range due to the long-distance seed dispersal that these bats offer. Without this, certain plant species could be negatively affected. (Menkhorst, 1995; Parry-Jones and Augee, 2001)

  • Ecosystem Impact
  • disperses seeds
  • pollinates

Economic Importance for Humans: Positive

Since P. poliocephalus eats many different fruits and nectars, it is an important pollinator, especially for certain Eucalyptus species. They are also important in transporting and distributing the seeds long distances. Therefore, there is a great possibility that a population reduction of this bat would have some negative long-term impacts on the regeneration of Australia’s forests. As a result of habitat destruction decreasing their range, they have thus had a reduction in migratory patterns, which, too, may lead to negative consequences for the ecosystem and for humans. (Menkhorst, 1995; Parry-Jones and Augee, 2001)

  • Positive Impacts
  • pollinates crops

Economic Importance for Humans: Negative

Pteropus poliocephalus is often believed to be detrimental to cultivated fruit crops, and thus farmers sometimes view the species as a pest. However, these bats only resort to eating fruit crops when other food sources become sparse. They are also thought to be a potential carrier of viral pathogens. ("Threatened Species Information: Grey-headed Flying-fox", 2001; NSW Scientific Committee, 2001; Richards, 1984)

Conservation Status

At one time P. poliocephalus had a much larger range; however, that range is now shrinking due to habitat destruction. Many areas of their habitat are becoming increasingly urbanized, such as in S.E. Queensland and northern New South Wales (NSW). Also, conservation reserves are limited, and in NSW < 15% of suitable habitat is within these reserves. (NSW Scientific Committee, 2001)

The main threat to P. poliocephalus is the destruction of habitat through deforestation. Females are particularly subject to spontaneous abortions due to loss of habitat and food sources, or when they are disturbed at the nesting site during the last few weeks of pregnancy. There are no regulations pertaining to the shooting of these animals, and farmers whose crops are perceived as being threatened often kill them. These bats also suffer from the tendency to fly into power lines, thus dying from electrocution. Black flying-foxes (Pteropus alecto) also pose a threat because they are competitors over food and habitat, and P. poliocephalus has been known to mate and thus hybridize with them. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Nowak, 1999; NSW Scientific Committee, 2001)

Currently this species is listed as vulnerable under the NSW Threatened Species Conservation Act 1995, schedule 2, and under the Environment Protection and Biodiversity Conservation Act 1999. It was at one point estimated that the population numbered somewhere in the millions. Recently, however, figures indicate that the population has had an approximately 30% decline over the last 10 years. However, not all organizations view this species as being threatened. It is listed on CITES as being of least concern, and not even present in a number of other threatened and/or endangered databases. ("Threatened Species Information: Grey-headed Flying-fox", 2001; Menkhorst, 1995; NSW Scientific Committee, 2001)

Other Comments

Measures taken of flight speed for P. poliocephalus in a wind tunnel showed values between (21 to 24 km/h); however, higher values (49, 52, and 63 km/h) indicate that at times the bats can obtain faster speeds with assistance from wind currents. (Tidemann and Nelson, 2004)

Contributors

Christina DeHaven (author), University of Alaska Fairbanks, Link E. Olson (editor, instructor), University of Alaska Fairbanks, Nancy Shefferly (editor), Animal Diversity Web.

Glossary

Australian

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

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.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

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.

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.

fertilization

union of egg and spermatozoan

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

monogamous

Having one mate at a time.

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.

nocturnal

active during the night

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).

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

seasonal breeding

breeding is confined to a particular season

sexual

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

social

associates with others of its species; forms social groups.

suburban

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

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

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

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

2001. "Threatened Species Information: Grey-headed Flying-fox" (On-line pdf). NSW National Parks and Wildlife Service. Accessed November 13, 2004 at http://www.nationalparks.nsw.gov.au/PDFs/tsprofile_greyheaded_flyingfox.pdf.

Feldhamer, G., L. Drickamer, S. Vessey, J. Merritt. 2004. Mammalogy: Adaptation, Diversity, Ecology 2nd edition. New York: McGraw-Hill.

Kunz, T., A. Stern. 1995. Maternal investment and post-natal growth in bats. Zoological Society of London Symposia, 67: 123-138.

McNab, B., F. Bonaccorso. 1995. The energetics of pteropodid bats. Zoological Society of London Symposia, 67: 111-122.

Menkhorst, P. 1995. Grey-headed Flying-fox. Pp. 156-158 in P Menkhorst, ed. Mammals of Victoria. Melbourne: Oxford University Press.

Menkhorst, P. 2001. Field Guide to Mammals of Australia. Melbourne: Oxford University Press.

NSW Scientific Committee, 2001. "Grey-headed flying fox - vulnerable species listing" (On-line). NSW National Parks and Wildlife Service. Accessed November 15, 2004 at http://www.nationalparks.nsw.gov.au/npws.nsf/Content/Grey-headed+flying+fox+-+vulnerable+species+listing.

Nowak, R. 1999. Walker's Mammals of the World 6th ed. Baltimore: Johns Hopkins University Press.

Parry-Jones, K., M. Augee. 2001. Factors affecting the occupation of a colony site in Sydney, New South Wales by the Grey-headed Flying-fox Pteropus poliocephalus (Pteropodidae). Austral Ecology, 26/1: 47-55.

Richards, G. 1984. Grey-headed Flying-fox. Pp. 274-276 in R Strahan, ed. The Australian Museum Complete Book of Australian Mammals: The National Photographic Index of Australian Wildlife. London: Angus and Robertson Publishers.

Taylor, J. 1984. The Oxford Guide To: Mammals of Australia. Melbourne: Oxford University Press.

Tidemann, C. 1995. Grey-headed Flying-Fox. Pp. 439-441 in R Strahan, ed. Mammals of Australia. Washington, D.C.: Smithsonian Institution Press.

Tidemann, C., J. Nelson. 2004. Long-distance movements of the grey-headed flying fox (Pteropus poliocephalus). Journal of Zoology, 263/2: 141-146.

Webb, N., C. Tidemann. 1996. Mobility of Australian flying-foxes, Pteropus spp. (Megachiroptera): evidence from genetic variation. Proceedings: Biological Sciences, 263/1369: 497-502.

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