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Why are flying-foxes important? These large bats are vegetarians. Their diet is mainly nectar, pollen and fruit. While feeding they perform important ecological functions for the plants supplying their food.
Pollination
Flying-foxes are important pollinators in eucalyptus forests and woodlands of eastern and northern Australia. While feeding on nectar and pollen in flowers, pollen grains stick to their fur. Some pollen is eaten during grooming and some is carried to other flowers to fertilise the ovules which then develop into seeds.
Pollen can also be transported by birds, bees (including native stingless bees), moths, butterflies, wasps, flies, beetles, other small mammals such as sugar gliders and the wind.
Eucalyptus trees need pollen from other trees of their species (outcrossing) to produce fertile seed. Flying-foxes are able to move between flowering trees which are widely separated. They can travel up to 100 kilometres in a night although most feeding is done within 25 kilometres of their daytime camp. Other pollinators operate over much smaller areas.
Dispersal of Rainforest Seeds
Flying-foxes carry seeds larger that 4 mm diameter in their mouths and small seeds may pass through their guts. By dispersing rainforest seeds over wide areas flying-foxes give seeds a chance to grow away from the parent plant.
Much of Australia's rainforest occurs as isolated patches surrounded by farmland or eucalyptus forest. Flying-foxes move seeds between these patches of rainforest including over cleared land. They provide essential genetic links across the landscape.
For such processes to take place animals like flying-foxes need to be in large numbers.
The Vital Jigsaw of Life
Life on earth is a complex jigsaw, each plant or animal being connected to others by complex processes we call ecological functions. Some examples of ecological functions are pollination, seed dispersal, decomposition of wood after death by termites and fungi so that the elements can be reused by the next generation, providing food resources.
Conservation of Flying-fox Populations
Conservation of flying-foxes depends on: - protecting their colony sites whether they are used permanently, annually or occasionally
- protecting large areas of forests, woodlands and heathlands throughout the landscape to provide food throughout the year
- protect and regenerate the mosaic of diet species across the landscape on both public and privately owned land.
Grey-headed Flying-foxes (Pteropus poliocephalus) have adapted their feeding strategies. They have adapted to Australia's unpredictable climate and low nutrient soils.
Australia experiences climatic extremes from prolonged droughts to periods of flooding rains. This combined with mostly low nutrient soils results in unreliable flowering in the eucalypt forests. Nectar and pollen production varies considerably from year to year.
Most eucalyptus species flower well about every fourth year, some more or less often.
Different species flower at different times throughout the year.
Nomads go where the food is.
Grey-headed flying-foxes adapt to this unreliable food resource by being nomadic. When a species of tree flowers well in a particular part of their range, tens of thousands of flying-foxes will congregate to feed on the blossom. Radio tracking of individual flying-foxes has confirmed that individuals move many hundreds of kilometres to prolific flowering. Observations of the population fluctuations at colony sites is consistent with variations in food resources around colony sites and elsewhere in their range.
Loss or reduction at any point in the annual food resource could cause a devastating effect on the population. For grey-headed flying-foxes, further reduction in the area of forest red gum Eucalyptus tereticornis or paperbarks Melaleuca quinquinervia in the north-east or spotted gum Corymbia (Eucalyptus) maculata on the south coast or white and yellow box Eucalyptus albens, E. melliodora on the western slopes of NSW could cause large numbers to die from starvation. This in turn could ultimately affect the regeneration of these tree species.
The Grey-headed Flying-foxes Pteropus poliocephalus has been recommended for listing as vulnerable in the Australian Bat Action Plan being compiled by the Commonwealth Government There is a consensus view among specialist bat researchers that this species is of conservation concern primarily because of projected habitat loss. Serious concern for the conservation of this species is based on the curtailment of their ecological role due to further loss and simplification of forests over all land tenures. This could be exacerbated by unco-ordinated and inappropriate regional forest agreements which do not recognise the annual feeding requirements of nomadic species. Projected urban expansion in coastal areas of NSW will also reduce food resources on which the species relies annually.
Further decrease in over all population could curtail their ecological role in maintaining forest diversity by eucalypt pollination and seed dispersal of rainforest species.
It is a commonly held belief that species occurring in large numbers such as flying-foxes are not endangered. Unfortunately this is a fallacy. The population of the migratory North American passenger pigeon dropped from billions to extinction over a 40 year period as a result of changes to its habitat and harvesting for urban markets. Long before a species becomes extinct, its population could be reduced to a point where it fails to perform its essential ecosystem functions eg. pollination, seed dispersal.
What can you do?
Talk to other people about the importance of flying-foxes.
Help protect forests containing their food resources.
Help protect colony sites.
Help protect and regenerate diet species on public and private land.
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