Pteropus poliocephalus

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.

• Biogeographic Regions
• australian australian
  • native native

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• forest forest
• rainforest rainforest

• Wetlands
• swamp swamp

• Other Habitat Features
• suburban suburban
• agricultural agricultural
• riparian riparian

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.

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

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.

• Mating System
• monogamous monogamous

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.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
• viviparous viviparous

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.

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 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.

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.

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.

• Key Behaviors
• arboreal arboreal
• flies
• nocturnal nocturnal
• motile motile
• migratory migratory
• territorial territorial
• social social
• colonial colonial

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.

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.

• Communication Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

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.

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.

• Primary Diet
• herbivore herbivore
  • frugivore frugivore

• 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.

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.

• 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.

• 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.

• Negative Impacts
• crop pest
• causes or carries domestic animal disease causes or carries domestic animal disease

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.

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.

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.

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.

Additional Links

Encyclopedia of Life

Contributors

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

References

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 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 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 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.

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 .