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.
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 ; tactile ; acoustic ; chemical
Other Communication Modes: scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
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.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: vulnerable
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
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
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
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.
Plant Foods: leaves; wood, bark, or stems; fruit; nectar; pollen; flowers
Primary Diet: herbivore (Frugivore )
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 (Native )
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.
Range elevation: 700 (high) m.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: forest ; rainforest
Wetlands: swamp
Other Habitat Features: suburban ; agricultural ; riparian
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.
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.
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.
Range mass: 600 to 1000 g.
Average mass: 677 g.
Range length: 230 to 289 mm.
Average length: 253 mm.
Average wingspan: 1 m.
Average basal metabolic rate: 316.2 cm3.O2/g/hr.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
Average basal metabolic rate: 1.768 W.
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.
Known Predators:
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
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.
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 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 (male): 30 months.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous
Average birth mass: 80 g.
Average number of offspring: 1.
Average age at sexual or reproductive maturity (male)
Sex: male: 540 days.
Average age at sexual or reproductive maturity (female)
Sex: female: 540 days.
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 ; 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)
