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
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
- tropical
- terrestrial
- Terrestrial Biomes
- forest
- rainforest
- Wetlands
- swamp
- Other Habitat Features
- suburban
- agricultural
- 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
- homoiothermic
- 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
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
- seasonal breeding
- gonochoric/gonochoristic/dioecious (sexes separate)
- sexual
- fertilization
- 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
-
pre-fertilization
- provisioning
-
protecting
- female
-
pre-hatching/birth
-
provisioning
- female
-
protecting
- male
- female
-
provisioning
-
pre-weaning/fledging
-
provisioning
- female
-
protecting
- male
- female
-
provisioning
-
pre-independence
-
provisioning
- female
-
protecting
- male
- female
-
provisioning
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.
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.
- Other Communication Modes
- scent marks
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.
- 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
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
Contributors
Christina DeHaven (author), University of Alaska Fairbanks, Link E. Olson (editor, instructor), University of Alaska Fairbanks, Nancy Shefferly (editor), Animal Diversity Web.
- Australian
-
Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.
- native range
-
the area in which the animal is naturally found, the region in which it is endemic.
- 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).
- tropical
-
the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.
- terrestrial
-
Living on the ground.
- forest
-
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
- 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.
- swamp
-
a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.
- suburban
-
living in residential areas on the outskirts of large cities or towns.
- agricultural
-
living in landscapes dominated by human agriculture.
- riparian
-
Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).
- 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.
- 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.
- monogamous
-
Having one mate at a time.
- 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).
- 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
- fertilization
-
union of egg and spermatozoan
- viviparous
-
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
- 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.
- nocturnal
-
active during the night
- motile
-
having the capacity to move from one place to another.
- migratory
-
makes seasonal movements between breeding and wintering grounds
- 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
- social
-
associates with others of its species; forms social groups.
- 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.
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- scent marks
-
communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them
- visual
-
uses sight to communicate
- tactile
-
uses touch to communicate
- acoustic
-
uses sound to communicate
- chemical
-
uses smells or other chemicals to communicate
- causes or carries domestic animal disease
-
either directly causes, or indirectly transmits, a disease to a domestic animal
- herbivore
-
An animal that eats mainly plants or parts of plants.
- frugivore
-
an animal that mainly eats fruit
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 .