Grey-headed Flying Fox
Encyclopedia
The Grey-headed Flying-Fox, Pteropus poliocephalus, is a megabat
native to Australia
.
Members of the genus Pteropus
include the largest bats in the world. The Pteropus genus has currently about 57 recognised species.
Pteropus is primarily an island taxon, with 55 species having some or all of their distribution on island
s. Only nine species are found in continental areas (five in Asia and four in Australia), and three (Lyle's flying-fox Pteropus lylei, little red flying-fox Pteropus scapulatus and the grey-headed flying-fox) are restricted to continents. The grey-headed flying-fox is very long-lived for a mammal of its size. There are reports of individuals surviving in captivity for up to 22 years, and a maximum age of up to 15 years seems possible in the wild.
The Grey-Headed Flying-Fox is the largest bat in Australia. It is tailless with claws on its first and second digits. Since it does not echolocate, it lacks tragus or leaf-ornamentation found in most species of Microchiroptera. It relies on sight to locate its food
(nectar, pollen and native fruits) and thus has large eyes. The flying-fox has a dark grey body with a light grey head and a reddish-brown neck collar of fur. It is unique among bats of the genus Pteropus in that fur on the legs extends all the way to the ankle. Adult grey-headed flying-foxes have an average wingspan of over 1m and can weigh up to 1 kg. 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.
Pteropus
: the little red flying-fox, Pteropus scapulatus, the spectacled flying-fox, Pteropus conspicillatus, the black flying-fox, Pteropus alecto and the grey-headed flying-fox. The grey-headed flying-fox is endemic to the south-eastern forested areas of Australia, principally east of the Great Dividing Range
. It extends from Finches Hatton in southern Queensland
to Geelong
, Victoria
, where it occupies a more extreme latitude than any other Pteropus species. Recently camps have been observed in Adelaide. Flying-foxes are preyed on by eagles
, goannas and snakes, as well as crocodiles.
, mangrove
s and riparian vegetation, but roosts also occupy highly modified vegetation in urban areas. A prominent example is the Royal Botanic Gardens in Sydney
, home to a colony that at its summer peak contains over 22,000 flying-foxes. Movements of the Grey Headed Flying-Fox are influenced by the availability of food. Their population is very fluid as they move in response to the irregular blossoming of certain plant species. The Grey-headed flying-fox is a partial migrant that uses winds to facilitate long-distance movement. It does not migrate in a specific direction, but rather in the direction that will be the most beneficial at the time.
Around dusk, grey-headed flying-foxes leave the roost and travel up to 50 km a night to feed on pollen, nectar and fruit. The food sources utilised by the species are fruit flowers and pollens from up to 187 plant species. Theses include Eucalyptus
, particularly Eucalyptus gummifera
, Eucalyptus muellerana
, Eucalyptus globoidea
and Eucalyptus botryoides
, and fruits from a wide range of rainforest trees, including members of the Ficus
genus. These bats are considered sequential specialists since on a variety of foods. Grey-headed flying-foxes, along with the three other Australian flying-fox species, fulfil a very important ecological role by dispersing the pollen and seeds of a wide range of native Australian plants. The grey-headed flying-fox is the only mammalian nectarivore
and frugivore
to occupy substantial areas of subtropical rainforests and so is of key importance to those forests.
Most vegetation communities used by the grey-headed flying-fox produce foraging resources in seasonal but annually irregular superabundant pulses, and the grey-headed flying-fox has adopted complex migration traits in response to such ephemeral and patchy food resources. However, there are some temporally and spatially reliable resources restricted to a small number of coastal vegetation communities in northern New South Wales
and Queensland
that may support smaller resident populations. The time when flying-foxes leave their roosts to feed depends on foraging light and predation risk. Flying-foxes have more time and light when foraging if they leave their roosts early in the day. The onset of a colony-wide emergence was gets delayed when a diurnal avian predator is present, whereas the onset is advanced for females during lactation when presumably energetic demands are higher. The emergence time of adult males depended on their social status: smaller bachelor males emerged from the colony earlier than larger harem-holding males who guard their harems until the last female had left. The flying-foxes that leave the roost earlier are more vulnerable to predation and some other flying-foxes will wait for others to leave, a phenomenon labelled the "after you" effect.
is about 27 weeks and pregnant females give birth between late September and November. Late births into January are sometimes observed. The young are born altricial
and are dependent on their mothers for regulation of temperature. Females carry their young for the first three weeks during their nightly foraging trips and after this time young are left in the roost at night. Young are capable of independent flight when they are approximately 4 months old at which time they commence foraging outside the colony. Young are weaned when they are approximately 6 months old.
Grey-headed flying-foxes are exposed to several threatening processes, including loss of foraging and roosting habitat, competition with the black flying-fox, and mass die-offs caused by extreme temperature events. When present in urban environments grey-headed flying-foxes are sometimes perceived as a nuisance. Cultivated orchard fruits are also taken but apparently only at times when other food items are scarce. Because the roosting and foraging habits of the grey-headed flying-fox bring the species into conflict with humans, the species suffers from direct killing of animals in orchards and harassment and destruction of roosts. Negative public perception of the species has intensified with the discovery of three recently emerged zoonotic
virus
es that are potentially fatal to humans: Hendra virus, Australian bat lyssavirus
and Menangle virus
. However, only Australian bat lyssavirus is known from two isolated cases to be directly transmissible from bats to humans.
Recent research has shown that since 1994, more than 24,500 grey-headed flying-foxes have died from extreme heat events alone. This is of increasing concern for the survival of this species now that climate models predict significant increases in the intensity, duration and frequency of such temperature extremes.
To answer some of the growing threats, roost sites have been legally protected since 1986 in New South Wales and since 1994 in Queensland. In 1999 the species was classified as ‘Vulnerable to extinction’ in The Action Plan for Australian Bats http://www.environment.gov.au/biodiversity/threatened/publications/action/bats/13.html, and has since been protected across its range under Australian federal law. As of 2008 on the IUCN Red List of Threatened Species.
Bat carers are not only specially trained in techniques to rescue and rehabilitate bats, they are also vaccinated against rabies. Although the chance of contracting the rabies-like Australian bat lyssavirus is extremely small, bat carers are inoculated for their own protection.
Flying-foxes often come to the attention of Australian wildlife care and rescue organisations such as Wildcare Australia, ONARR, Wildlife Carers Darling Downs, Bat Care, Bat Rescue, Tweed Valley Wildlife Carers, WIRES
and Wildlife Victoria when reported as injured, sick, orphaned or abandoned. A very high proportion of adult flying-fox injuries are caused by entanglement in barbed wire fences or loose, improperly erected fruit tree netting, both of which can result in very serious injuries and a slow, agonising death for the animal if not rescued quickly.
Baby flying-foxes usually come into care after having been separated from the mother. Babies are often orphaned during 4 to 6 weeks of age when they inadvertently fall off the mother during flight. When they are older, orphans usually come into care because of maternal death from power line electrocution or barbed wire entanglement. A rare, but apparent natural, occurrence of mass abandonment can lead to the rescue of hundreds of babies at one time. The latter most recently occurred in November 2008 at the Canungra bat camp in South East Queensland when Wildcare Australia, working closely with the EPA and regional bat care groups, rescued and rehabilitated over 300 baby Grey-headed Flying-foxes. Most babies are in a dehydrated and distressed state by the time they are rescued, and some are infested with maggots if found sick or injured. A young flying-fox must be fed every 4 hours up to 6 times a day, and then as it develops it is introduced to blossoms and fruit. When the young flying-fox is fully weaned around 10 to 12 weeks of age, it goes into a crèche for rehabilitation and eventual release.
Megabat
Megabats constitute the suborder Megachiroptera, family Pteropodidae of the order Chiroptera . They are also called fruit bats, old world fruit bats, or flying foxes.-Description:...
native to Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
.
Members of the genus Pteropus
Pteropus
Bats of the genus Pteropus, belonging to the megabat or Megachiroptera sub-order, are the largest bats in the world. They are commonly known as the fruit bats or flying foxes among other colloquial names...
include the largest bats in the world. The Pteropus genus has currently about 57 recognised species.
Pteropus is primarily an island taxon, with 55 species having some or all of their distribution on island
Island
An island or isle is any piece of sub-continental land that is surrounded by water. Very small islands such as emergent land features on atolls can be called islets, cays or keys. An island in a river or lake may be called an eyot , or holm...
s. Only nine species are found in continental areas (five in Asia and four in Australia), and three (Lyle's flying-fox Pteropus lylei, little red flying-fox Pteropus scapulatus and the grey-headed flying-fox) are restricted to continents. The grey-headed flying-fox is very long-lived for a mammal of its size. There are reports of individuals surviving in captivity for up to 22 years, and a maximum age of up to 15 years seems possible in the wild.
Physical characteristics
Food
Food is any substance consumed to provide nutritional support for the body. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, or minerals...
(nectar, pollen and native fruits) and thus has large eyes. The flying-fox has a dark grey body with a light grey head and a reddish-brown neck collar of fur. It is unique among bats of the genus Pteropus in that fur on the legs extends all the way to the ankle. Adult grey-headed flying-foxes have an average wingspan of over 1m and can weigh up to 1 kg. 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.
Ecology
The Australian mainland is home to 75 species of bat. Of these, four species belong to the genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
Pteropus
Pteropus
Bats of the genus Pteropus, belonging to the megabat or Megachiroptera sub-order, are the largest bats in the world. They are commonly known as the fruit bats or flying foxes among other colloquial names...
: the little red flying-fox, Pteropus scapulatus, the spectacled flying-fox, Pteropus conspicillatus, the black flying-fox, Pteropus alecto and the grey-headed flying-fox. The grey-headed flying-fox is endemic to the south-eastern forested areas of Australia, principally east of the Great Dividing Range
Great Dividing Range
The Great Dividing Range, or the Eastern Highlands, is Australia's most substantial mountain range and the third longest in the world. The range stretches more than 3,500 km from Dauan Island off the northeastern tip of Queensland, running the entire length of the eastern coastline through...
. It extends from Finches Hatton in southern Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
to Geelong
Geelong, Victoria
Geelong is a port city located on Corio Bay and the Barwon River, in the state of Victoria, Australia, south-west of the state capital; Melbourne. It is the second most populated city in Victoria and the fifth most populated non-capital city in Australia...
, Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
, where it occupies a more extreme latitude than any other Pteropus species. Recently camps have been observed in Adelaide. Flying-foxes are preyed on by eagles
Eagles
The Eagles are an American rock band formed in Los Angeles, California in 1971 by Glenn Frey, Don Henley, Bernie Leadon, and Randy Meisner.With five number one singles, six Grammys, five American Music Awards, and six number one albums, the Eagles were one of the most successful musical acts of the...
, goannas and snakes, as well as crocodiles.
Habitat and movements
Grey-headed flying-foxes live a variety of habitats including rainforests, woodlands and swamps. During the day individuals reside in large roosts (colonies or 'camps') consisting of hundreds to tens of thousands of individuals. Colonies are formed in seemingly arbitrary locations. Roost vegetation includes rainforest patches, stands of MelaleucaMelaleuca
Melaleuca is a genus of plants in the myrtle family Myrtaceae known for its natural soothing and cleansing properties. There are well over 200 recognised species, most of which are endemic to Australia...
, mangrove
Mangrove
Mangroves are various kinds of trees up to medium height and shrubs that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes N and S...
s and riparian vegetation, but roosts also occupy highly modified vegetation in urban areas. A prominent example is the Royal Botanic Gardens in Sydney
Royal Botanic Gardens, Sydney
The Royal Botanic Gardens in Sydney, Australia, are the most central of the three major botanical gardens open to the public in Sydney....
, home to a colony that at its summer peak contains over 22,000 flying-foxes. Movements of the Grey Headed Flying-Fox are influenced by the availability of food. Their population is very fluid as they move in response to the irregular blossoming of certain plant species. The Grey-headed flying-fox is a partial migrant that uses winds to facilitate long-distance movement. It does not migrate in a specific direction, but rather in the direction that will be the most beneficial at the time.
Diet and foraging
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...
, particularly Eucalyptus gummifera
Corymbia gummifera
Corymbia gummifera, commonly known as Red Bloodwood, is a hardwood tree native to eastern Australia.-Description:It usually grows as a tree, but may take the form of a mallee in very poor soils. As a tree it typically grows to a height of 20 to 34 metres and a trunk diameter of one metre dbh....
, Eucalyptus muellerana
Eucalyptus muelleriana
Eucalyptus muelleriana, commonly known as Yellow Stringybark, is a species of Eucalyptus which is native to New South Wales and Victoria in Australia. It is a tall tree, growing up to 40 metres in height.-References:*...
, Eucalyptus globoidea
Eucalyptus globoidea
Eucalyptus globoidea, known by the common name White Stringybark, is a tree native to eastern Australia. It has thick, fibrous bark usually colored light gray over reddish brown. It is also known for its distinctive glossy green leaves in its adult life...
and Eucalyptus botryoides
Eucalyptus botryoides
Eucalyptus botryoides, Bangalay or Southern Mahogany, is a small to tall tree. The height may be up to 40 metres. Rough bark covers the trunk and larger branches, is thick, fibrous, and grey-brown to red-brown....
, and fruits from a wide range of rainforest trees, including members of the Ficus
Ficus
Ficus is a genus of about 850 species of woody trees, shrubs, vines, epiphytes, and hemiepiphyte in the family Moraceae. Collectively known as fig trees or figs, they are native throughout the tropics with a few species extending into the semi-warm temperate zone. The Common Fig Ficus is a genus of...
genus. These bats are considered sequential specialists since on a variety of foods. Grey-headed flying-foxes, along with the three other Australian flying-fox species, fulfil a very important ecological role by dispersing the pollen and seeds of a wide range of native Australian plants. The grey-headed flying-fox is the only mammalian nectarivore
Nectarivore
In zoology, nectarivore is an animal which eats the sugar-rich nectar produced by flowering plants. Most nectarivores are insects or birds, but there are also nectarivorous mammals, notably several species of bats in the Southwestern United States and Mexico, as well as the Australian Honey Possum...
and frugivore
Frugivore
A frugivore is a fruit eater. It can be any type of herbivore or omnivore where fruit is a preferred food type. Because approximately 20% of all mammalian herbivores also eat fruit, frugivory is considered to be common among mammals. Since frugivores eat a lot of fruit they are highly dependent...
to occupy substantial areas of subtropical rainforests and so is of key importance to those forests.
Most vegetation communities used by the grey-headed flying-fox produce foraging resources in seasonal but annually irregular superabundant pulses, and the grey-headed flying-fox has adopted complex migration traits in response to such ephemeral and patchy food resources. However, there are some temporally and spatially reliable resources restricted to a small number of coastal vegetation communities in northern New South Wales
New South Wales
New South Wales is a state of :Australia, located in the east of the country. It is bordered by Queensland, Victoria and South Australia to the north, south and west respectively. To the east, the state is bordered by the Tasman Sea, which forms part of the Pacific Ocean. New South Wales...
and Queensland
Queensland
Queensland is a state of Australia, occupying the north-eastern section of the mainland continent. It is bordered by the Northern Territory, South Australia and New South Wales to the west, south-west and south respectively. To the east, Queensland is bordered by the Coral Sea and Pacific Ocean...
that may support smaller resident populations. The time when flying-foxes leave their roosts to feed depends on foraging light and predation risk. Flying-foxes have more time and light when foraging if they leave their roosts early in the day. The onset of a colony-wide emergence was gets delayed when a diurnal avian predator is present, whereas the onset is advanced for females during lactation when presumably energetic demands are higher. The emergence time of adult males depended on their social status: smaller bachelor males emerged from the colony earlier than larger harem-holding males who guard their harems until the last female had left. The flying-foxes that leave the roost earlier are more vulnerable to predation and some other flying-foxes will wait for others to leave, a phenomenon labelled the "after you" effect.
Social behavior
Groupings and territories
Grey-headed flying-foxes form two different roosting camps, summer camps and winter camps. Summer camps are used from September to April or June. It is in these camps that the flying-foxes establish territories, mate and reproduce. Winter camps are used from April to September. Winter camps tend to be segregated between sexes with little agnostic behaviour and more mutual grooming. Summer camps are considered "main camps" while winter camps are referred to as "transit camps" In their summer camps, starting in January, male grey-headed flying-foxes sent up mating territories which contain harems of up to five females. Mating territories are generally 3.5 body lengths along branches. The flying-foxes have neck glands which enlarge in males in the mating season and are used to mark the territories, usually entire branches. Males also maintain territories though aggressive behaviour. The territorial system has been described as similar to a lek system. The males fight to maintain costly territories with the most dominant males occupying the centre of the roosting site. The females move from the periphery into the central territories and form into harems. However, the territories may have values other than the males themselves as they do provide a place for females to roost. Centrally located males are polygamous while males on the periphery seem to be more monogamous as they form mixed-sex groups with females that were still nursing their young from the previous year.Mating
Matings are generally observed between March and May but the most likely time of conception is April. Most mating takes place in the territories and during the day. Females have power in initiation and termination of copulations and thus a male will mate several times with the same female for up to an hour and multiple mating sessions with the same female over the course of several days. The majority of females reproduce once a year and give birth to a single young. GestationGestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
is about 27 weeks and pregnant females give birth between late September and November. Late births into January are sometimes observed. The young are born altricial
Altricial
Altricial, meaning "requiring nourishment", refers to a pattern of growth and development in organisms which are incapable of moving around on their own soon after hatching or being born...
and are dependent on their mothers for regulation of temperature. Females carry their young for the first three weeks during their nightly foraging trips and after this time young are left in the roost at night. Young are capable of independent flight when they are approximately 4 months old at which time they commence foraging outside the colony. Young are weaned when they are approximately 6 months old.
Conservation
The grey-headed flying-fox is now a prominent federal conservation problem in Australia. Early last century the species was considered abundant with numbers estimated in the many millions. However, in recent years, direct evidence has been accumulating that the species is in serious decline. Current estimates for the species are about 300,000 and it has been suggested that the national population may have declined by as much as 30% between 1989 and 1999 alone.Grey-headed flying-foxes are exposed to several threatening processes, including loss of foraging and roosting habitat, competition with the black flying-fox, and mass die-offs caused by extreme temperature events. When present in urban environments grey-headed flying-foxes are sometimes perceived as a nuisance. Cultivated orchard fruits are also taken but apparently only at times when other food items are scarce. Because the roosting and foraging habits of the grey-headed flying-fox bring the species into conflict with humans, the species suffers from direct killing of animals in orchards and harassment and destruction of roosts. Negative public perception of the species has intensified with the discovery of three recently emerged zoonotic
Zoonosis
A zoonosis or zoonoseis any infectious disease that can be transmitted from non-human animals to humans or from humans to non-human animals . In a study of 1415 pathogens known to affect humans, 61% were zoonotic...
virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
es that are potentially fatal to humans: Hendra virus, Australian bat lyssavirus
Australian bat lyssavirus
Australian bat lyssavirus is a zoonotic virus closely related to rabies virus. It was first identified in a 5-month old juvenile Black Flying Fox collected near Ballina in northern New South Wales, Australia in 1996 during a national surveillance program for the recently identified Hendra virus...
and Menangle virus
Menangle virus
Menangle virus is a virus that infects pigs, humans and bats.-History:Menangle virus was first identified in 1997 after a piggery in Menangle near Sydney, NSW, Australia experienced a high number of stillbirths and deformities during farrowing. Two workers at the piggery came down with an...
. However, only Australian bat lyssavirus is known from two isolated cases to be directly transmissible from bats to humans.
Recent research has shown that since 1994, more than 24,500 grey-headed flying-foxes have died from extreme heat events alone. This is of increasing concern for the survival of this species now that climate models predict significant increases in the intensity, duration and frequency of such temperature extremes.
To answer some of the growing threats, roost sites have been legally protected since 1986 in New South Wales and since 1994 in Queensland. In 1999 the species was classified as ‘Vulnerable to extinction’ in The Action Plan for Australian Bats http://www.environment.gov.au/biodiversity/threatened/publications/action/bats/13.html, and has since been protected across its range under Australian federal law. As of 2008 on the IUCN Red List of Threatened Species.
Wildlife rescue
Flying-foxes often come to the attention of Australian wildlife care and rescue organisations such as Wildcare Australia, ONARR, Wildlife Carers Darling Downs, Bat Care, Bat Rescue, Tweed Valley Wildlife Carers, WIRES
NSW Wildlife Information and Rescue Service
WIRES - NSW Wildlife Information Rescue and Education Service isthe largest wildlife rehabilitation charity in Australia. It is a non-profit organisation providing rescue and rehabilitation for all native Australian fauna. All animal rescuers and carers are volunteers...
and Wildlife Victoria when reported as injured, sick, orphaned or abandoned. A very high proportion of adult flying-fox injuries are caused by entanglement in barbed wire fences or loose, improperly erected fruit tree netting, both of which can result in very serious injuries and a slow, agonising death for the animal if not rescued quickly.
Baby flying-foxes usually come into care after having been separated from the mother. Babies are often orphaned during 4 to 6 weeks of age when they inadvertently fall off the mother during flight. When they are older, orphans usually come into care because of maternal death from power line electrocution or barbed wire entanglement. A rare, but apparent natural, occurrence of mass abandonment can lead to the rescue of hundreds of babies at one time. The latter most recently occurred in November 2008 at the Canungra bat camp in South East Queensland when Wildcare Australia, working closely with the EPA and regional bat care groups, rescued and rehabilitated over 300 baby Grey-headed Flying-foxes. Most babies are in a dehydrated and distressed state by the time they are rescued, and some are infested with maggots if found sick or injured. A young flying-fox must be fed every 4 hours up to 6 times a day, and then as it develops it is introduced to blossoms and fruit. When the young flying-fox is fully weaned around 10 to 12 weeks of age, it goes into a crèche for rehabilitation and eventual release.
Further reading
- Welbergen, J.A. (2001). First year report: The social organisation of the Grey-Headed Flying-Fox, Pteropus poliocephalus: colony composition and behaviour. The Department of Zoology; University of Cambridge, Cambridge.