Project flying fox resources

Student project resources are provided to assist students with the completion of the Project flying fox program.

About the Grey-headed flying fox

The grey-headed flying fox (Pteropus poliocephalus) is a megabat native to Australia. It is only found in south-eastern forested areas of Australia (including towns and cities), mainly east of the Great Dividing Range. Its range extends approximately from Bundaberg in Quensland to to Geelong in Victoria.

Find out where your local flying fox colony is located and the number of flying foxes there.

The grey-headed flying fox is the largest bat in Australia. This 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. Adults have an average wingspan up to 1 m 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 1,000 g, with an average of 677 g. It is tailless, with claws on its first and second digits. It relies on sight to locate its food (nectar, pollen and native fruits) and thus has relatively large eyes for a bat.

The grey-headed flying fox is long-lived for a mammal of its size. Individuals reportedly survived in captivity for up to 23 years, and a maximum age of up to 15 years seems possible in the wild.

Habitat and movements

Grey-headed flying foxes live in 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 melaleuca, (paperbark) mangroves, and riverside vegetation, but roosts also occupy highly modified vegetation in urban areas. A famous colony lived in the Royal Botanic Gardens in Sydney. However, the Garden instituted a policy to remove them from the garden grounds by playing loud noise to disturb them. The camp is now dispersed across Queensland.

Movements of grey-headed flying foxes are influenced by the availability of food. Their population changes 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 - where they eat

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 species eats fruit flowers and pollens of around 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 they feed on a variety of foods. Grey-headed flying foxes, along with the three other Australian flying fox species, fulfill 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, so is of key importance to those forests.

Most vegetation communities on which this species forages produce nectar and pollen seasonally and are abundant unpredictably, so the flying fox’s migration traits cope with this. The time when flying foxes leave their roosts to feed depends on foraging light and predator risk. Flying foxes have more time and light when foraging if they leave their roosts early in the day. The entire colony may leave later if a predatory bird is present, while lactating females (mothers living milk) leave earlier. With males, the bachelors leave earlier than harem-holding males, which guard their wait until all their females have left. The flying foxes that leave the roost earlier are more vulnerable to predators, and some other flying foxes will wait for others to leave, a phenomenon labelled the “after you” effect

Predators

Flying foxes are preyed on by eagles, goannas, and snakes, as well as crocodiles.

Social organisation

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. In these camps, they establish territories, mate, and reproduce. Winter camps are used from April to September. The sexes are separated in winter camps and most behaviour is characterised by 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 set up mating territories. Mating territories are generally 3.5 body lengths along branches. These flying foxes’ neck glands enlarge in males in the mating season, and are used to mark the territories. The males fight to maintain their territories, and this is associated with a steep drop in the males’ body condition during this time. Around the beginning of the mating season, adult females move from the periphery towards the central male territories where they become part of short-term ‘harems’ that consist of a male and an unstable group of up to five females. Centrally located males are polygamous, (mate with several females) while males on the periphery are monogamous (mate with one female) or single. The mating system of the grey-headed flying fox is best described as a lek because males do not provide any essential resources to females and are chosen on the basis of their physical location within the roost, which correlates with male quality.

Although recorded in small numbers sporadically throughout twentieth century it was not until the 1980s that Grey-headed flying foxes routinely visited Melbourne. Since the 1990s their permanent colony in Melbourne has been postulated as possibly due to habit loss in their northern range, greater supply of reliable food by native eucalypt plantings and backyard fruit trees, climate change, and increase urbanisation leading to warmer temperatures.

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 control over the copulation process, and males may have to keep mating with the same females. Females usually give birth to one young each year. Pregnancy lasts around 27 weeks, and pregnant females give birth between late September and November. Late births into January are sometimes observed. The newborns rely on their mothers for warmth. For their first three weeks, young cling to their mothers when they go foraging. After this, the young remain in the roosts. By January, young are capable of sustained flight, and by February, March or April are fully weaned.

Why they are endangered

Threats

Grey-headed flying foxes are exposed to several threats, 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 their roosting and foraging habits bring the species into conflict with humans, they suffer 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 viruses 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.

Conservation

The grey-headed flying fox is now a prominent federal conservation problem in Australia. Early in the last century, the species was considered abundant, with numbers estimated in the many millions. In recent years, though, direct evidence has been accumulating that the species is in serious decline. Current estimates for the species are about 300,000, and the national population may have declined by over 30% between 1989 and 1999 alone. Find out more about why they are vulnerable and what can be done to help protect them by looking at the websites below:

Source – Wikipedia