Pteropus poliocephalus
gray-headed flying fox

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)

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)