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Culling flying-foxes is ineffective, so why suggest slaughter?

Flying-foxes are taking refuge in populated areas, and people are deciding they don’t like them. James Reed

Culling flying-foxes is ineffective, so why suggest slaughter?

Animosity towards the grey-headed flying-fox has intensified as their contact with humans has increased. Last month, the Queensland government announced that it would issue an annual quota of 1280 permits for farmers to shoot them where they are causing crop damage. Pressure to implement mass culls is also mounting.

Grey-headed flying-foxes (Pteropus poliocephalus) are highly environmentally significant. By spending their nights foraging over extensive areas, they disperse pollen and seeds throughout landscapes. With a diet of over 100 flowering and fleshy fruited trees - including numerous eucalypt, melaleuca and banksia species - the flying-fox fundamentally binds together various strands of life into an interdependent web.

Despite this, the flying-fox has a public relations problem. To many orchardists, they are much feared harbingers of lost productivity. Widespread vegetation clearing along Australia’s eastern coastal strip has left the flying-fox with limited natural foraging grounds, and in times of food scarcity they seek out horticultural crops. Because of the nomadic nature of their colonies, damage is generally low and intermittent, but in some years crop losses are substantial.

It has also become increasingly common for flying-foxes to use urban areas, where they can exploit cultivated plants in parks and gardens. But here too, they have often found themselves unwelcome. To most people, their raucous camps are noisy, smelly, disease-ridden, and generally incongruous with the austere and regimented control we have come to expect from our urban landscapes.

Paul Hocksenar

A grey area - vulnerable or not?

In 2001, the grey-headed flying-fox was listed as a “vulnerable species” under the national Environment Protection and Biodiversity Conservation Act and the NSW Threatened Species Conservation Act. The population size at time of its listing was not low: there were around 320,000 to 400,000 individuals throughout their range, which spans the coastal regions of Queensland, New South Wales and Victoria.

But rarity is only one aspect of vulnerability to extinction. Even abundant species can slip into extinction when faced with rapidly dwindling population numbers, as tragically illustrated by the North American passenger pigeon.

Census counts revealed the grey-headed flying-fox had declined by 30% since 1989, due primarily to loss of key winter foraging habitat. Based on this, it was listed as vulnerable to extinction. The listing heralded a major shift in management goals towards conservation; previously, there had been a long history of indiscriminate persecution.

The current status of this flying-fox is debated among researchers, and there have been calls for it to be de-listed due to an apparent expanding population size. A national census throughout its range has not been conducted since 2005. That survey documented 674,000 individuals – up from 425,000 the previous year.

The high count was attributed to inexperienced survey staff and inclusion of data from previously undiscovered camps. Certainly, such a rapid increase could not have been due to fecundity alone, since the flying-fox produces only one pup per year. Nonetheless, census data from 1998 to 2005 do not show a trend of systematic population decline.

The B@t/Flickr

In the absence of a comprehensive survey since 2005, it is difficult to determine the grey-headed flying-fox’s current conservation status. However, it is not inconceivable that they are one of the few native mammals that have found a way to thrive in human-altered landscapes when their natural habitat is stripped away. Sadly, even if such a resilience were documented in future census data, it could prove to be bitter-sweet.

Attack is not the best defence

Population recovery is the ultimate goal of threatened species management: a rare victory to be celebrated. But in the case of the grey-headed flying-fox, it would likely be used – erroneously – as a justification for expanding culling programs.

Culling is an ineffective way of responding to conflicts between flying-foxes and people. When a large aggregation of flying-foxes descends upon an orchard to forage, shooting by an individual farmer has a negligible impact on population numbers. It does little to prevent crop damage.

Achieving local eradication through mass culls is also doomed to failure. Because they migrate over long distances in response to food availability, culling a local population of flying-foxes creates a vacant niche. This draws in more animals from farther afield, which are then also culled. This vicious cycle has been described as a “pteropucidal black hole”.

More obviously, if grey-headed flying-fox numbers are recovering after a period of decline, it does not make sense to then beat them back into submission with bullets. We risk substituting the threatening process of loss of natural foraging habitat with one of human hatred. It would render wasted all the hard work by flying-fox conservationists over the last 10 years and lead us back to square one – or worse.

Our approaches to conflict with flying-foxes need to become more sophisticated than simply killing them. In the case of the grey-headed flying-fox, the vulnerable listing prompted discussion, research and funding for the implementation for non-lethal means of trying to resolve some of these tensions. If populations are indeed rebounding by taking refuge in human-altered landscapes, our commitment to finding ways of managing this – without reducing them to pitiful heaps of fur – will need to be just as great.