Enumerating a continental-scale threat: How many feral cats are in Australia?

Authors: S Legge, BP Murphy, H McGregor, JCZ Woinarski, J Augusteyn, G Ballard, M Baseler, T Buckmaster, CR Dickman, T Doherty, G Edwards, T Eyre, BA Fancourt, D Ferguson, DM Forsyth, WL Geary, M Gentle, G Gillespie, L Greenwood, R Hohnen, S Hume, CN Johnson, M Maxwell, PJ McDonald, K Morris, K Moseby, T Newsome, D Nimmo, R Paltridge, D Ramsey, J Read, A Rendall, M Rich, E Ritchie, J Rowland, J Short, D Stoked, DR Sutherland, AF Wayne, L Woodford and F Zewe.

Published in: Biological Conservation

Abstract

Feral cats (Felis catus) have devastated wildlife globally. In Australia, feral cats are implicated in most recent mammal extinctions and continue to threaten native species. Cat control is a high-profile priority for Australian policy, research and management.

To develop the evidence-base to support this priority, we first review information on cat presence/absence on Australian islands and mainland cat-proof exclosures, finding that cats occur across >99.8% of Australia’s land area. Next, we collate 91 site-based feral cat density estimates in Australia and examine the influence of environmental and geographic influences on density.

We extrapolate from this analysis to estimate that the feral cat population in natural environments fluctuates between 1.4 million (95% confidence interval: 1.0–2.3 million) after continent-wide droughts, to 5.6 million (95% CI: 2.5–11 million) after extensive wet periods. We estimate another 0.7 million feral cats occur in Australia’s highly modified environments (urban areas, rubbish dumps, intensive farms).

Feral cat densities are higher on small islands than the mainland, but similar inside and outside conservation land. Mainland cats reach highest densities in arid/semi-arid areas after wet periods. Regional variation in cat densities corresponds closely with attrition rates for native mammal fauna.

The overall population estimate for Australia’s feral cats (in natural and highly modified environments), fluctuating between 2.1 and 6.3 million, is lower than previous estimates, and Australian feral cat densities are lower than reported for North America and Europe. Nevertheless, cats inflict severe impacts on Australian fauna, reflecting the sensitivity of Australia’s native species to cats and reinforcing that policy, research and management to reduce their impacts is critical.

Legge, S, et al (2016) Enumerating a continental-scale threat: How many feral cats are in Australia? Biological Conservation PDF DOI

 

Impacts and management of feral cats Felis catus in Australia

Authors: Tim S Doherty, Chris R Dickman, Chris N Johnson, Sarah M Legge, Euan G Ritchie and John CZ Woinarski

Published in: Mammal Review (early view)

Abstract

Feral cats are among the most damaging invasive species worldwide, and are implicated in many extinctions, especially in Australia, New Zealand and other islands. Understanding and reducing their impacts is a global conservation priority.

We review knowledge about the impacts and management of feral cats in Australia, and identify priorities for research and management.

In Australia, the most well understood and significant impact of feral cats is predation on threatened mammals. Other impacts include predation on other vertebrates, resource competition, and disease transmission, but knowledge of these impacts remains limited.

Lethal control is the most common form of management, particularly via specifically designed poison baits. Non-lethal techniques include the management of fire, grazing, food, and trophic cascades. Managing interactions between these processes is key to success.

Given limitations on the efficacy of feral cat management, conservation of threatened mammals has required the establishment of insurance populations on predator-free islands and in fenced mainland enclosures.

Research and management priorities are to: prevent feral cats from driving threatened species to extinction; assess the efficacy of new management tools; trial options for control via ecosystem management; and increase the potential for native fauna to coexist with feral cats.

Doherty TS, Dickman CR, Johnson CN, Legge SM, Ritchie EG, Woinarski JCZ (2016) Impacts and management of feral cats Felis catus in Australia. Mammal Review PDF DOI

Raising the Bar: How making peace with predators could transform our world

Why are some feral animals running rampant? Should we reintroduce dingoes and Tasmanian devils to parts of Australia? Why doesn’t shark culling work? How can predators help us to fight climate change? Recorded live at Belleville Melbourne.

via SoundCloud

Phylogeography of the antilopine wallaroos (Macropus antilopinus) across tropical northern Australia

Authors: Jessica J Wadley, Damien A Fordham, Vicki A Thomson, Euan G Ritchie and Jeremy J Austin

Published in: Ecology and Evolution (early view)

Abstract

The distribution of antilopine wallaroo, Macropus antilopinus, is marked by a break in the species’ range between Queensland and the Northern Territory, coinciding with the Carpentarian barrier.

Previous work on M. antilopinus revealed limited genetic differentiation between the Northern Territory and Queensland M. antilopinus populations across this barrier. The study also identified a number of divergent lineages in the Northern Territory, but was unable to elucidate any geographic structure.

Here, we re-examine these results to (1) determine phylogeographic patterns across the range of M. antilopinus and (2) infer the biogeographic barriers associated with these patterns.

The tropical savannahs of northern Australia: from the Cape York Peninsula in the east, to the Kimberley in the west. We examined phylogeographic patterns in M. antilopinus using a larger number of samples and three mtDNA genes: NADH dehydrogenase subunit 2, cytochrome b, and the control region. Two datasets were generated and analyzed: (1) a subset of samples with all three mtDNA regions concatenated together and (2) all samples for just control region sequences that included samples from the previous study. Analysis included generating phylogenetic trees based on Bayesian analysis and intraspecific median-joining networks.

The contemporary spatial structure of M. antilopinus mtDNA lineages revealed five shallow clades and a sixth, divergent lineage. The genetic differences that we found between Queensland and Northern Territory M. antilopinus samples confirmed the split in the geographic distribution of the species. We also found weak genetic differentiation between Northern Territory samples and those from the Kimberley region of Western Australia, possibly due to the Kimberley Plateau–Arnhem Land barrier. Within the Northern Territory, two clades appear to be parapatric in the west, while another two clades are broadly sympatric across the Northern Territory. MtDNA diversity of M. antilopinus revealed an unexpectedly complex evolutionary history involving multiple sympatric and parapatric mtDNA clades across northern Australia.

These phylogeographic patterns highlight the importance of investigating genetic variation across distributions of species and integrating this information into biodiversity conservation.

Wadley JJ, Fordham DA, Thomson VA, Ritchie EG, Austin JJ (2016) Phylogeography of the antilopine wallaroo (Macropus antilopinus) across tropical northern Australia. Ecology and Evolution PDF DOI 

 

The Conversation: Why Victoria’s dingo and ‘wild dog’ bounty is doomed to miss its target

By Euan Ritchie (Deakin University) and Arian Wallach (University of Technology Sydney)

Dingo-crosshairs

Dingo bounties are a really, really bad idea.

On any given night, many farmers go to sleep worrying about what they might wake up to in the morning. Few things are more stressful than seeing your livestock, such as sheep, lying dead or seriously injured in the paddock. Sometimes dingoes, free roaming and unowned (“feral”) dogs, and domestic dogs, or their hybrids, are responsible for such a scene. But what’s the best way to deal with this situation?

The Victorian government is set to reinstate a dingo and wild dog bounty scheme as a way to reduce livestock, especially sheep, being attacked and killed, in response to calls from farming and shooting groups.

Just what is a dingo?

One of the problems with managing dingoes is that the boundary between them and “wild dogs” is contentious. Some have even claimed that there are no pure dingoes in Victoria.

Defining what dingoes are is harder than you might think. There is considerable variation in how dingoes look, for example, in terms of their overall size and colour, as is common with many other members of the dog family (canids).

And if a dingo isn’t considered 100% “pure”, containing genes from domestic dogs, should hybrids be managed differently to dingoes?

Research suggests “pure” dingoes do exist in Victoria, albeit in smaller numbers than other regions.

Notably though, genetic samples in Victoria have been collected largely from areas close to towns, where there are likely more hybrid dogs, and less so from deep within Victoria’s more remote natural regions (the mallee, alpine, and Gippsland forests), where dingoes are often sighted.

Two other recent studies are important in the Victorian context. One suggests dingo characteristics prevail even within hybrids and another has found there are two distinct dingo populations. Importantly, the south east dingo population is at increased risk of extinction.

Many ecologists would argue that splitting hairs about dingo genetic “purity” is a moot point, because what really matters is what dingoes and dingo-dog hybrids are doing in the environment. This is because dingoes are known to have important ecological roles, including the suppression of feral species (such as cats, pigs, and goats), red foxes, and kangaroos.

How are wild dogs and dingoes managed in Victoria?

The decision to reinstate a dingo and wild dog bounty in Victoria is vexed. In 2007 the Victorian government established protection of dingoes, due to conservation concerns about the species, with hybridisation between dingoes and domestic dogs identified as a threatening process.

As a result, dingoes in Victoria are listed as a threatened species under the Flora and Fauna Guarantee Act 1988 and protected under the Wildlife Act 1975.

In Victoria wild dogs are classed as pest animals and can be legally controlled. However, the Victorian Department of Environment states that “dingoes are visually indistinguishable from wild dogs, making it impossible to ensure they are not inadvertently destroyed in wild dog control programs in any given area where both exist” and “dingoes are protected wildlife and it is an offence under the Wildlife Act 1975 to take or kill protected wildlife without an authorisation to do so”.

Management misfire

Legal and species identification issues aside, do bounties and lethal control of predators actually work?

In short, scientific evidence suggests the answer is largely no (see for instance here, here, here, here, and here).

There are a range of reasons cited for why bounties fail. These include:

  • an inability to sufficiently reduce numbers of the the target species and hence their impact, due to rapid breeding and/or immigration from other areas
  • corruption by those claiming bounties, whereby animals claimed for bounty payments have not actually been killed in the area where the bounty is intended to benefit
  • an inability to access some animals over large and/or remote areas
  • a disincentive to completely eradicate animals as this removes the source of income
  • disruption of predator social structures causing higher livestock predation.

Investing in predator-friendly farming

So what solutions do we have that might allow productive farms without the need to kill predators? A range of nonlethal solutions exist for protecting livestock, including improved husbandry techniques (such as corralling and herding), and in particular, a growing body of research suggests guardian animals provide a great step forward.

Nonlethal methods to protect livestock are also consistent with a growing social demand that both domestic and wild animals are treated humanely and ethically on farms.

Predator-friendly farming is growing across Australia, as you can see in the image above. Large livestock on large landholdings, such as beef cattle on thousands of square kilometre stations, are reducing conflict by enabling dingo packs to stabilize and by supporting healthier cows that are better able to defend their calves (top left).

Smaller farms are also employing protective strategies, including guardian dogs, even if the livestock species is large, such as dairy cows and buffalo, because lethal control on neighboring farms continues to disrupt the dingo’s social structure (bottom left).

Technological innovations in nonlethal methods for protecting livestock from predators have been developed in Australia and used worldwide, such as “Foxlights” (top right). And vulnerable stock, such as chickens, are being successfully protected with guardian dogs and enclosures (bottom right).

There are substantial gains to be made for agriculture, people, wild animals and the environment if decision-makers use scientific evidence and ethical analysis, rather than responding to lobby groups, as the basis for taxpayer-sponsored actions.

Education is also a key aspect of any change, and scientists are being proactive here too, providing guidance on new approaches to rangeland livestock management that are supported by research.

The fact is, bounty schemes don’t work. If instead the substantial funds currently being invested in bounties were invested in supporting farmers to move to more long-term, cost-effective, and more environmentally-friendly solutions, we may all be able to sleep better at night.

This article was originally published on The Conversation. Read the original article, including reader comments.

The Conversation
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