Botanic Gardens Trust, Sydney, Australia

Flying-foxes

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What are flying-foxes? flying-foxes are large bats, weighing up to 1 kg, with a wing span which may exceed one metre. They sleep during the day and feed on pollen, nectar and fruit at night. In the wild they are important pollinators and seed dispersers of native trees. Seeds are discarded in the faeces or fall where the fruit is being eaten. These seeds germinate when conditions are suitable and ensure that dispersal occurs in a wide area.

What species are the flying-foxes at the Royal Botanic Garden Sydney? Flying-foxes, otherwise known as fruit bats, are mammals, and are members of the Pteropodidae family. They have the largest body size of all bats. The grey-headed flying-fox is the largest member of the family. Most flying-foxes at the Royal Botanic Garden are grey-headed flying-foxes (Pteropus poliocephalus), which are listed as vulnerable under both NSW and Commonwealth legislation. There is also a small number of black flying-foxes (Pteropus alecto), typically a more tropical species, which began roosting in the Royal Botanic Garden around 2006.

Are grey-headed flying-foxes found elsewhere in the world? No. The grey-headed flying-fox is a native species that is endemic to Australia.

Where in Australia can they be found? Eastern Australia: Queensland, New South Wales, Victoria.

What is the natural habitat of the grey-headed flying-fox? Forests, woodlands, intertidal mangroves.

How many grey-headed flying-foxes are there in Australia? There are currently estimated to be less than 450,000 grey-headed flying-foxes in Australia. The species suffered a population decline of around 30 per cent over the 10 years between 1989 and 1999, which contributed to its listing as a threatened species. It is believed that the species is still rapidly declining due to the continuation of the key threats to the species.

How can you identify whether a bat is a grey-headed flying-fox? The grey-headed flying-fox has a mostly dark grey body and grey head (occasionally with ‘blonde’ flecks), with a rusty brown coloured collar. It is also the only bat to have fur from the top of its head right down to its toes. The fur of the black flying-fox only goes part-way down the leg.

How big are grey-headed flying-foxes? This species is the largest bat in Australia and can weigh up to one kilogram. It has the longest wingspan of any bat with a maximum wingspan of about one metre (3 feet).  Its body length is normally between 22 and 27 centimetres (8.5 to 10.5 inches).

Can grey-headed flying-foxes see? All bats can see, but unlike the small insect-eating bats (otherwise known as micro-bats) that use echolocation (emitting high frequency sounds that bounce off objects to allow the bats to find their way around in pitch darkness) to find their food, the pollen, nectar and fruit-eating flying-foxes (otherwise known as mega-bats) use sight and smell to find their food. Their vision is just as good as ours during the day and even better at night.

What is the breeding cycle of grey-headed flying-foxes? Both the grey-headed flying-fox and the black flying-fox give birth once a year, usually to only one young. Although both species will mate all year round, they usually all conceive around late April. Conception is followed by a gestation period of six months, after which most young are born in October/November. For the first three weeks after birth, the females carry their dependent young with them on their foraging flights. By the age of around five to six months, the young should be fully weaned and foraging with the adults. They are relatively long-lived mammals with the average age of reproductive animals between six and ten years. Sexual maturity is reached after two to three years.

What is a flying-fox camp? The term camp is generally used to refer to a site where flying-foxes regularly roost, rather than referring to a group of a particular number of flying-foxes e.g. the flying-foxes have made the Royal Botanic Garden in Sydney a ‘permanent’ camp, which is occupied all year round. However, there are ‘annual’ camps that the flying-foxes use at the same time every year, and also ‘irregular’ camps that the flying-foxes may roost in occasionally if there is a nearby food source available at the time.

flying-foxes do prefer roosting together in large numbers (hundreds or thousands). Occasionally a smaller group may roost in a location for a short period, but these small groups will usually either attract more flying-foxes to the site, or will move on to join other larger flying-fox camps. flying-foxes are very sociable and because they are so focussed on finding food in many different locations at night, they use ‘camps’ for social contact (as well as for rest) when they are all together during the day.

What do grey-headed flying-foxes eat? The favourite food of the grey-headed flying-fox is the nectar and pollen of eucalypts and other native trees, such as paperbarks and banksias. Flying-foxes also like eating rainforest fruits, such as figs and lilly pilly berries, which they chew to extract the juice and then spit out the fibre and the large seeds. Small seeds are often swallowed and may not pass through the gut until up to one hour later, by which time flying-foxes could be 35-50 km away from the tree that the seed came from. By dispersing rainforest seeds over wide areas, flying-foxes give seeds a chance to grow away from the parent plant, and potentially expand remnant patches of valuable rainforest vegetation. It is estimated that a single flying-fox can dispense up to 60,000 seeds in one night.

When do flying-foxes eat and sleep?

flying-foxes sleep during the day and feed on pollen, nectar and fruit at night. At dusk, flying-foxes depart from their camps to feed on various local food resources. As dawn approaches, some flying-foxes gradually start to return to camp from which they came, whereas others may fly to another nearby camp to rest for the day.

Why is the grey-headed flying-fox a protected species? Almost all native Australian animals are protected by law. However due to large and rapid reductions (e.g. 30 per cent decline over 10 years) in numbers of grey-headed flying-foxes (Pteropus poliocephalus), the species was listed as vulnerable in 2001 under both the NSW Threatened Species Conservation Act 1995 and the Commonwealth Environment Protection and Biodiversity Conservation Act 1999. This reduction in numbers was mainly due to loss of habitat of in Queensland and New South Wales due to large scale land clearing, as well as culling.

What makes the grey-headed flying-fox important to protect? Flying-foxes are important pollinators of the eucalypt forests and woodlands of eastern and northern Australia. Their main food source is the protein-rich pollen produced by Eucalyptus flowers. Eucalyptus trees need pollen from other trees of their species (out-crossing) to produce fertile seed, and the largely nomadic flying-foxes are very good at providing this transport service. While feeding on nectar and pollen in flowers, pollen grains stick to the fur of the flying-foxes. Some pollen is eaten during grooming, but some is carried on the fur to other flowers to fertilise the ovules which then develop into seeds. This pollen may be carried for very long distances (up to 100 km in one night) and across cleared land, which provides an essential genetic link between fragmented patches of native vegetation. Other pollinators, such as birds, bees (including native stingless bees), moths, butterflies, wasps, flies, beetles, other small mammals such as gliders and the wind, operate over much smaller areas.

Through pollination and seed dispersal, flying-foxes help to provide habitat for other flora and fauna species and also help to sustain Australia’s hardwood timber, honey and native plant industries. But to be effective in this role, flying-foxes need to be in large numbers.

What can be done to help the grey-headed flying-fox species survive? To protect flying-foxes from further decline and to help reduce their apparent need for taking refuge in urban and suburban areas (where food is reliable), it is vital that large areas of forests, woodlands and heathlands are protected throughout the landscape to provide food throughout the year. It is also important to regenerate the mosaic of diet species across the landscape. Over the last decade, there has been a significant increase in the protection of habitat on the east coast and ranges of NSW, with approximately 40 per cent of this area now protected in National Parks and Reserves.

flying Foxes

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