11 September 2012

Good or evil: what role for the dingo in Australia?

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When it comes to dingo management in Australia, there is an issue that is polarising scientists in the field and goes largely unmentioned in the media.
Dingo ecology_COSMOS science magazine

A dingo on Fraser Island, Australia. Incidents on Fraser Island have involved dingoes attacking and killing humans - grabbing headlines. But what is going unmentioned is an important debate taking place in the field: are dingoes ecologically beneficial or simply a pest? Credit: Silje L. Bakke

Australia’s approach to dingoes is characterised by conflicting and often extreme views on what roles the dingo should play, if any. This has largely come about due to high-profile cases, such as that of Azaria Chamberlain at Uluru and incidents on Fraser Island, where dingoes have attacked and killed humans. The consequences to humans, because of their tragic potential, are the ones that grab the headlines.

But what goes largely unmentioned is an issue that is polarising Australian scientists working in the field. Deceptively simple, it is this: are dingoes ecologically good or bad?

Other than humans, the dingo (Canis lupus dingo) is Australia’s largest land predator. Fossil records indicate it has been present on the mainland for at least 4,000 years. Certainly, indigenous Australians killed dingoes, but it was with the arrival of Europeans that intensive dingo control and exclusion has occurred. As testament to this, the ‘dingo fence’, which at 5,500 km is the world’s longest man-made structure, was erected to exclude dingoes from almost a quarter of Australia. Land managers in most States and Territories are compelled through legislation to destroy wild dogs, including dingoes, on their land.

From an agricultural perspective, there are sound reasons behind the extirpation of the dingo. In 2004, a conservative estimate by the Invasive Animals Co-operative Research Centre found that dingoes and other wild dogs cause $48.3 million dollars worth of damage to agricultural productivity annually. In light of this, if dingoes are also ecologically detrimental there is little reason to question Australia’s ongoing persecution of dingoes. However, if there are ecological benefits from dingoes, our approach to their management needs reconsideration and refinement. The possibility of their reintroduction needs to be contemplated.

The key argument for reintroduction is that dingoes are the top-order predator in Australia. Elsewhere, species in this category have been found to be beneficial, with their removal leading to increases in abundance of lower-order, mesopredators and subsequent trophic cascades leading to changes in herbivore communities and even plant community structure and hydrology. This concept of smaller predators erupting after the removal of larger ones is known as the ‘mesopredator release hypothesis’.

In most Australian ecosystems, red foxes and feral cats are the introduced mesopredators. Their predation on native animals has led to catastrophic declines in the populations of small- and medium-sized native mammals. Australia has one of the highest mammal extinction rates in the world: over the past 200 years, at least 22 mammals have become extinct. For years, predation by the red fox and feral cat on native fauna has been listed as a Key Threatening Process under Australian legislation and policy. Yet decades of attempts to control these species have largely failed. It is in these circumstances that future, positive management of the dingo could be critical to arrest the rate of mammal extinction.

In their 2009 book chapter “Reintroducing the Dingo: Can Australia’s Conservation Wastelands be Restored?” Christopher Dickman and colleagues from the University of Sydney questioned the appropriateness of Australia’s historical management of dingoes. They did not suggest that dingoes should be re-introduced to all areas where agriculture occurs. Rather, if the mesopredator release hypothesis applies to Australian ecosystems, then dingoes in some areas would have net positive effects and their positive management would be arbitrated.

Such proposals are highly controversial, both among scientists and stakeholders in dingo management. Depending on the implementation, reintroduction could have wide ranging impacts on multibillion-dollar pastoral, mining and tourism industries. At stake is the future of Australia’s agri-ecosystems, particularly the sheep industry, which is long-suffering from dingo and red fox impacts.

Research to address these ‘big questions’ in Australia is in its early stages. Indeed, our understanding of consequences of altering populations of dingoes in Australia is based on a handful of preliminary investigations. As yet, suppression of foxes and feral cats by dingoes has not been demonstrated by reintroduction experiments, nor has mesopredator release been demonstrated by dingo removal, although experiments are underway in northern Australia.

Internationally, the most high profile reintroduction program of a top-order predator involved wolves in Yellowstone National Park. Coyote sightings were extremely rare in the Greater Yellowstone area prior to European settlement when wolves were more common. After a period of wolf control in the early 1900’s, coyote harvest numbers increased dramatically; potentially an example of mesopredator release. More recently, since the reintroduction of wolves into Yellowstone National Park in 1995-96, coyote densities declined by 39% based on the work by Kim Berger and Eric Gese (2007).

This change in predator abundance is now the subject of much scientific study with trophic linkages shown among a suite of prey. For example, where wolves are now regulating numbers of their main prey (elk) the impacts (through overgrazing) on plant communities are being reversed as documented by Robert Beschta and William Ripple (2009) of Oregon State University through Aspen regeneration. These are excellent examples of how prey populations (elk) have been observed to change in association with the reintroduction of their main predator (wolves) and where a mesopredator (the coyote) appears to have been suppressed through interference competition from wolves.

The Yellowstone model, and other international studies, such as Eurasian lynx in Scandinavia, have further sparked interest in reintroducing dingoes into areas of Australia. In Britain, there is discussion about the reintroduction of lynx, brown bears, wolves and elk to the countryside centuries after they died out. David Bowman’s provocative suggestion published in Nature (2012) that elephants, rhinoceros and Komodo dragons may be the solution to controlling Australia’s feral animals is a little farfetched, but to date no funding or approval has been given for a comparable dingo reintroduction study in Australia to those undertaken internationally.

In a recent paper, Peter Fleming and his co-authors from Biosecurity NSW, proposed seven considerations that must be addressed before dingo populations are managed positively. These include:
• behavioural changes that could result when dingoes interbreed with domestic dogs
• the notion that humans are often the ‘top-predator’ in Australian ecosystems rather than the dingo
• the risk dingoes might pose to threatened species through predation
• the simultaneous impacts of control programs on dingo and fox numbers
• other processes that affect the population dynamics of threatened fauna
• variability in social and economic niches across Australia, and
• the influence of anthropogenic changes that could prevent dingoes fulfilling their pre-European ecological roles.

Clearly, we have a long way to go before these seven considerations are addressed. What is important to note though is that any reintroduction of the dingo will need to take account of the negative impacts that dingoes could have on human industries. The continued expansion of mining and tourism activities into remote locations makes that a certainty.

The point here is not to deter exploration of these important scientific investigations; in fact I strongly encourage it. It is to emphasise the complexity of the issues that need to be taken into account when we talk about dingoes. It is imperative not to get caught up in the hype of media riding on the back of a 30 year old mystery surrounding the death of Azaria Chamberlain. There is a deeper issue that could determine the future of Australia’s ecosystems. Whether we like it or not, it involves the dingo.

Thomas Newsome is a senior ecologist with the Snowy Mountains Engineering Corporation and Honorary Associate with the Desert Ecology Research Group at the University of Sydney, NSW. This article was co-written with Christopher Dickman of the University of Sydney, NSW, and Peter Fleming and Guy Ballard of Biosecurity NSW.
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