Grey-headed Flying-foxes (Pteropus poliocephalus)
What do they look like?
The Grey-headed Flying-fox (Pteropus poliocephalus) is an endemic mammal and the largest Australian bat. It has a wingspan that can reach one metre and body mass up to one kilogram.
It has pale grey fur on its head, rusty-coloured fur encircling the neck, grey belly fur with flecks of white and ginger, thick leg fur extending to the ankle and black wings.
The Grey-headed Flying-fox is the only flying-fox species that has a permanent presence in South Australia, and it is a nationally threatened species.
In South Australia, Grey-headed Flying-foxes are protected under the National Parks and Wildlife Act 1972. Nationally (and internationally) they are considered to be Vulnerable to extinction.
Grey-headed Flying-foxes occur in the coastal belt from central Queensland, through New South Wales, Victoria and into South Australia.
Although they gather in widely dispersed colonies across a vast area, Grey-headed Flying-foxes comprise a single population. Individuals from one colony may regularly move interstate and interact with other colonies. For example, one bat captured in Adelaide was tracked to Sydney.
Grey-headed Flying-fox distribution in Australia. Source: Species of national environmental significance 10 km grid, version 3
Commonwealth of Australia 2016 (www.environment.gov.au/science/erin/databases-maps/snes)
Grey-headed Flying-foxes are nocturnal foragers of flowering and fruiting plants. They find these foods using a strong sense of smell and large eyes suited to recognising colours at night.
Their diet is diverse, and they will feed in remnant native vegetation patches as well as in urban areas. They can also take advantage of new resources, including the fruits of cultivated trees, especially when their preferred food resources are limited.
Grey-headed Flying-foxes prefer to feed within 20 kilometres of their roost, but they can travel up to 50 kilometres away in search of food.
Foraging range of Grey-headed Flying-foxes from the Adelaide camp site; optimal foraging range is within 20 km of the camp site (inner circle), but bats may range up to 50 km from the camp (outer circle) each night in search of food.
Once a food resource is located, individuals may establish a feeding territory that they then defend. Feeding groups of up to six or more animals may occur in a single tree. Bats will squabble when individuals compete for a resource, but individual bats feeding in trees are often silent and can easily go unnoticed. Grey-headed Flying-foxes move through suburban areas and use local gardens all the time.
Bats will often return each night to the same resources until they are depleted.
Bat camps are critical sites for mating, giving birth and rearing young.
Grey-headed Flying-foxes will mate throughout the year, but conception typically occurs from March to May when the males become fertile.
Gestation lasts six months and females give birth to a single young or ‘pup’ around September to November. The pup clings to the mother’s belly and is carried by her for three to five weeks before being left in a crèche area of the bat camp at night.
The mothers return to camp just before dawn, find their pup using unique calls and smells, and suckle them. Mothers will wrap their wings around the pups to protect them during the day and in cold temperatures.
Pups are weaned at around five months, and, after some practice flying around the camp, they fly out with the adults at night to feed on flowers and fruits. Independent young are prone to misadventure and mortality rates are high during the first two years of life.
Grey-headed Flying-foxes are important pollinators and seed dispersers of a wide range of native Australian plants, including canopy trees and economically-important hardwoods.
Large bats provide long-distance dispersal of pollen and seeds, which is important for maintaining genetic diversity and healthy forests. They also play an important part in forest regeneration.
Grey-headed Flying-foxes are experiencing continued population decline and are at risk of extinction because of:
- loss of prime natural feeding habitats and camp sites
- slow reproductive rate (one young per year) and high juvenile mortality rates
- increasingly urbanised bat populations with increased potential conflict with humans
- legal and illegal destruction of bats in orchards, primarily in the eastern states
- effects of climate change across their natural range, including extreme heat events and decreased productivity in their food resources.
Flying foxes, including the Grey-headed Flying-fox, are natural reservoirs of several zoonotic diseases of livestock and humans, including Hendra virus and Australian bat lyssavirus.
They pose little human health risks unless a person is bitten or scratched. It is very important that you never handle any bat, including dead or injured bats. If you are bitten or scratched by a flying fox, wash the site immediately with plenty of soap and water and seek immediate medical attention. For more health information please refer to SA Health.
If you find an injured or dead bat, please contact a wildlife rescue organisation, such as Fauna Rescue or Adelaide Bat Care. Do not attempt to remove it yourself.
Australian bat lyssavirus
Incidences of Australian bat lyssavirus are extremely rare and preventable; prevalence of the virus in wild bats is also very low (less than one per cent). The virus is only transmitted by the saliva of an infected animal coming into contact with an open wound or mucus membrane such as the eyes, nose or mouth. Lyssavirus is not spread through bat droppings or urine, so people are not exposed to the virus if one flies overhead, feeds or roosts in their garden, or if they live near a camp or visit one.
Hendra virus outbreaks are extremely rare and there have been no cases in South Australia. There is no evidence that humans catch the virus directly from flying foxes. It appears that the virus may be transmitted from flying foxes to intermediate domestic animal hosts (particularly horses), and humans may then contract the virus from infected horses.
Transmission of the virus from bats to domestic horses probably occurs through the horses’ consumption of partially-chewed fruit contaminated with bat saliva, or incidental ingestion of bat urine or faeces beneath bat foraging sites. For more information about Hendra virus and horses visit the Department of Primary Industries and Regions South Australia (PIRSA).
Loss of natural habitats and urbanisation of flying fox populations increases the interactions among bats, humans and livestock, which may also be linked to the emergence of some bat-borne viruses. However, even in areas with relatively large urban bat populations, such as the greater Sydney area with at least 70,000 Grey-headed Flying-foxes in 11 camps, disease risks remain extremely low.