In recent years we in Australia have been forced to re-examine the way we treat the landscape of the "Lucky Country'. With blue-green algae in the river systems which are the life-line of the interior, salination of formally rich agricultural land, erosion problems, chemical pollutants and, most recently, over-allocation of water resources; our record in sustainable agricultural practices is nothing to be proud of. However, primary producers in many areas are leading the way in resolving landcare problems, primarily through local community-based groups. They are re-educating themselves and redefining best practice standards in Australian agriculture. Many are discovering that the basic information they require to resolve landcare issues is not available and they must be involved in finding answers themselves. These changes in Australian agriculture are occurring within the context of changes taking place in the community as a whole as public understanding and concern for many environmental issues grow.
Australian fruit growers, particularly those based on the coastal fringe of the country, have escaped many of the legacies of past agricultural practices being faced by their counterparts in the interior. Issues of environmental sustainability for many fruit growers center on mitigating erosion, monitoring the effects of chemicals used to control soil fertility, weeds and invertebrates, land use planning issues, vertebrate pest management practices, etc. Because fruit growing areas are increasingly surrounded by and acquired for urban and suburban development, many commercial fruit growers are dealing with their problems of environmental sustainability in a very public atmosphere. Neighbours who are not primary producers but may be affected by management practices on fruit crops often voice their concerns.
This paper examines one issue currently faced by fruit growers, flying fox management. It refers primarily to broad-based ecological management practices as they impinge on orchardists rather than on-crop management techniques. The paper summarises the changes that have occurred in flying fox management practices over the past five years, explains the ecological rationale for the changes and offers some predictions for the next five years. The aim is to encourage fruit growers to incorporate these predictions into their planning processes.
The primary difficulty in managing native animals that damage crops is that when they leave the crops they form part of natural system which continues to function around us and upon which we all depend. They take off the "black hat" of a crop pest and put on the "white hat" of an important component of our country's ecosystems. Crop management practices for these animals become entangled in broader ecosystem management policies in a direct and obvious way. Flying foxes provide a good example of this dichotomy.
The ecological importance of Australia's flying foxes lies in the way they feed on their native foods and the effects of their feeding behaviour on forests. Flying foxes are agents for seed dispersal and pollination in their food plants, and these functions are vital to reproduction and regeneration processes in the forests they inhabit. Flying foxes have two sources of native food, the flesh of fruit from rainforest trees and nectar and pollen from blossoms of trees from a range of species including rainforest species, eucalypts, banksias, paperbarks, etc. When they feed on fruit, flying foxes disperse seeds at two scales, in a localised area around fruiting trees and more substantial distances between successive feeding trees. Flying foxes are territorial feeders. Dominant animals defend fruit resources from sub-dominants which land in a fruiting tree, harvest fruit from the territories of dominants and carry the fruit away to feed. This activity results in seed dispersal over a radius of up to 300 m. In addition, individual animals use many fruiting trees during a night's feeding trip and transport seeds between them. These successive trees are located between 500 m and 6.5 km apart. By transporting seeds of native rainforest trees and vines away from parent plants, flying foxes increase the likelihood that they will germinate and successfully establish themselves. Seed dispersal also affects the patterns of plant distribution. It helps maintain the species diversity we all associate with rainforests and also the genetic integrity of plant populations. When flying foxes feed on blossom, their fur collects pollen which they also carry with them as they feed. Many species of plants in Australian forests, particularly eucalypts, cannot self-pollinate. They must receive viable pollen from other trees in order to set seeds. Blossom-feeding flying foxes fulfil this function.
There are a range of seed dispersers and pollinators in Australian forests, but flying foxes are exceptional in the distances that they carry seeds and pollen. They are also exceptional in their ability to adapt to environmental change brought about by humans. Flying foxes are highly flexible in their diets, in their foraging patterns, in their ability to cope with changes in the local abundance of food and in the distances they can travel to find food. The diet of Grey-headed flying foxes comprises over 100 species of native fruit and blossom and a range of introduced and commercial species. There are few limitations to their diets. For example, they do not differentiate between fruits based on their colour, their size or the size of their seeds. They have strategies to deal with all these traits, and that is unusual among frugivores. The distances individual Grey-headed flying foxes travel to forage on fruits is also highly variable. Some individuals fly short distances of about 2 km from their camps to single feeding trees. Others travel over 60 km round trip in a night and use many different trees. Animals fly further distances to feed on blossom. Total nightly flights of approximately 100 km have been recorded, and individuals use many trees when feeding on blossom.
These movements define seed dispersal and pollination patterns. Grey-headed flying foxes create wide-spread seed dispersal and pollination patterns around their camps. Their capacity to locate and move to fruiting or flowering trees is not inhibited by clearing. Grey-headed flying foxes fly many kilometers over cleared land when they move between feeding trees. This enables them to feed successfully despite forest clearing. It also enables them to transport pollen and seeds between isolated trees or between isolated patches of forest.
When the food levels around a camp diminish, animals may stay and forage close to the camp or roost near their feeding trees in order to save energy. However, the majority of animals migrate hundreds of kilometers to successive areas of flowering trees, primarily eucalypt species. The flowering patterns of eucalypts is irregular and influenced by temperature and rainfall. Because of this largely unpredictable pattern of flowering and because so much forested are has been cleared, Grey-headed flying foxes are nomadic. They have the capacity to move hundreds of kilometers between areas of flowering trees which do not occur in the same place or at the same time every year. It is not a regular, annual migration.
This flexibility in diet, in foraging patterns and in migratory patterns has allowed flying foxes to survive the high levels of forest clearing which have occurred in eastern Australia. It means that, unlike many seed dispersers and pollinators, they can continue to fulfil these roles in highly fragmented habitat such as agricultural land. It is one of their ecological strengths. It makes them very important to plant reproduction in remnant patches of forest and to the sustainability of rainforest and eucalypt forest communities in these tiny patches. But it is a fruit grower's nightmare because this flexibility enables flying foxes to locate and feed on a range of crops; and it is impossible to control numbers in a local area because the animals gather from over such long distances.
Historically, management policies for Australian flying foxes have been driven by the high levels of damage they irregularly cause to commercial fruit crops, by the inconvenience to local residents of large aggregations of animals in camps near their homes and, more recently, by the effects of roosting animals on subtropical rainforest vegetation. Traditional management practices for flying foxes aim to control their numbers and rely heavily on programs of culling. There are various accounts of mass exterminations in N.S.W. using guns, explosives, chemicals, etc. which date from the time of European settlement. Although methods of controlling flying foxes which destroy animals remain the preferred management option of many fruit growers and of other groups affected by camps, there is no evidence that these techniques provide long-term solutions to management issues. There is no evidence that they solve the problem of flying fox damage for the commercial fruit industry. To date the only effective method for keeping flying foxes out of crops is full exclusion netting.
Although flying foxes are vital to forest ecosystems, their beneficial ecological roles have seldom been recognised or accommodated in management practices. They have been managed as pests and, in part because of this their numbers are decreasing. Drops in flying fox numbers have been caused both by habitat loss and by culling. The majority of animals rely on eucalypt blossom throughout the year and massive clearing of eucalypt forests and woodlands results in food bottlenecks or periods of inadequate blossom production. During these times, animals do not reproduce successfully and many die. When a bottleneck occurs during fruiting seasons, flying foxes turn to commercial fruits and unknown numbers of animals are additionally culled on crops. As a result, both Grey-headed flying foxes and Spectacled flying foxes in far north Queensland require urgent conservation attention. They are beginning to receive it through legislative changes. Flying foxes are now Protected species in every state and territory in Australia. It is no longer legal to destroy or disturb animals in their camps. While currently fruit growers can obtain licences to shoot them on their crops, orchardists cannot expect that situation to last for Grey-headed flying foxes.
In recent years both N.S.W. and Queensland have enacted Endangered Species legislation. That legislation requires that the conservation status of each species of vertebrate fauna be assessed in each state and that they be classified according to their degree of vulnerability. Animals are classified as Not Threatened, Vulnerable, Rare, Endangered, etc. Each of these classifications carries with it statutory responsibilities for different levels of management and conservation action. There was a time when these words were used freely and the processes used to define status were essentially arbitrary, but that is no longer the case. There is a clearly defined system used to assess the conservation status of species. This means that animals are no longer given Endangered status without good defendable reasons. It also means that if there is a conservation problem for any species, public opinion can no longer keep those animals from receiving the level of protection they require. As one would expect, there is a constant review process. If the situation for a species deteriorates, it can be granted a higher level of protection and attention at short notice. On the other hand, if, for example, a recovery program for an Endangered species is successful its classification can be adjusted accordingly.
The current conservation status of Grey-headed flying foxes makes them candidates for inclusion on Vulnerable species lists in N.S.W. and Queensland. When that happens, under the terms of Endangered Species legislation, licensed culling on fruit crops will no longer be legal. The Queensland National Parks and Wildlife Service has recognised that the conservation classification of Grey-headed flying foxes is likely to change and has negotiated with fruit growers a phase down period for licensed culling on crops. Growers are being encouraged to take advantage of low interest loans available for netting through the Rural Adjustment Authority. Over the next five years, licences for culling will be progressively phased down for crops which are suitable for netting. This procedure provides fruit growers with a transition period. It is important that alternate non-destructive management techniques, such as nets, be put in place or that methods to deter flying foxes be developed as a matter of priority so that fruit growers will not be left with no on-crop methods for control when Vulnerable status is conferred and enforced.
If flying foxes were introduced species with no beneficial role in ecosystem function in Australia, then fruit growers would probably continue to manage them on their crops with little interference or scrutiny. But that has never been the case. While flying foxes have been perceived as pest species since Europeans arrived in Australia, they have always, in fact, been an integral part of forest survival. The degree to which the forests of eastern Australia have been modified increases the importance of Grey-headed flying foxes to conservation policies which stress ecological sustainability. At the same time, forest loss and culling practices have decreased the likelihood of their survival. Management strategies for the animals are shifting in response. Fruit growers will be affected and must plan for the change.
Additional reading:
Eby, P. 1991. "Finger-winged night workers": managing forests to conserve the role of Grey-headed flying foxes as pollinators and seed dispersers. In D. L. Lunney (ed), Conservation of Australia's Forest Fauna. Pp. 91-100. Royal Zoological Society of NSW, Mosman.
Slack, J. (ed), 1990. Flying fox workshop proceedings. N.S.W. Agriculture and Fisheries, Lismore, N.S.W.
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