The bark side: domestic dogs threaten endangered species worldwide


File 20170430 12979 apfd4b
A feral dog chasing a wild boar, Banni grasslands, India.
Chetan Misher/Facebook

Tim Doherty, Deakin University; Aaron J. Wirsing, University of Washington; Chris Dickman, University of Sydney; Dale Nimmo, Charles Sturt University; Euan Ritchie, Deakin University, and Thomas Newsome, Deakin University

Humans and their canine companions share many close bonds. Wolves (Canis lupus) were the first animal domesticated by people, some time between 15,000 and 50,000 years ago. The Conversation

There are now an estimated 1 billion domestic dogs across their near-global distribution.

Domestic dogs include feral and free-ranging animals (such as village and camp dogs), as well as those that are owned by and completely dependent on humans (pet dogs).

Our latest research reveals that the ecological “pawprint” of domestic dogs is much greater than previously realised.

Using the IUCN Red List of Threatened Species, we counted how many species are negatively affected by dogs, assessed the prevalence of different types of impacts, and identified regions with the greatest number of affected species.

A dog with a black-naped hare, Maharashtra, India.
Hari Somashekhar/Facebook

Dogs are third-most-damaging mammal

We found that dogs are implicated in the extinction of at least 11 species, including the Hawaiian Rail and the Tonga Ground Skink. Dogs are also a known or potential threat to 188 threatened species worldwide: 96 mammal, 78 bird, 22 reptile and three amphibian species. This includes 30 critically endangered species, two of which are classed as “possibly extinct”.

These numbers place dogs in the number three spot after cats and rodents as the world’s most damaging invasive mammalian predators.

Even though dogs have an almost global distribution, the threatened species they are known to affect are concentrated in certain parts of the globe. South-East Asia, South America, Central America and the Caribbean each contain 28 to 30 threatened species impacted by dogs. Other hotspots include Australia, Micro/Mela/Polynesia and the remainder of Asia.

Regional concentrations of threatened species negatively impacted by domestic dogs.
Author provided

Lethal and non-lethal impacts

Predation was the most commonly reported impact of dogs on wildlife. The typically omnivorous diet of dogs means they have strong potential to affect a diversity of species. For instance, dogs killed at least 19 endangered Kagu (a ground-dwelling bird) in New Caledonia in 14 weeks. Threatened species with small population sizes are particularly vulnerable to such intense bouts of predation.

The frequency of different types of dog impact on threatened species.
https://authors.elsevier.com/a/1Uxs~1R~e71Xl

Aside from simply killing animals, dogs can harm wildlife in other ways, such as by spreading disease, interbreeding with other canids, competing for resources such as food or shelter, and causing disturbances by chasing or harassment. For example, contact with domestic dogs increases disease risk for endangered African Wild Dogs in Kenya.

Part of the problem is that when wild animals perceive dogs as a threat, they may change their behaviour to avoid them. One study near Sydney found that dog walking in parklands and national parks reduced the abundance and species richness of birds, even when dogs were restrained on leads.

None of the Red List assessments mentioned such indirect risk effects, which suggests that their frequency is likely to be much higher than reported.

Feral dogs chasing Indian wild ass at Little Rann of Kutch, India.
Kalyan Varma/Facebook

Friend and foe

Despite their widespread and sometimes severe impacts on biodiversity, dogs can also benefit some species and ecosystems.

For example, in Australia, the closely related dingo (Canis dingo) can suppress populations of introduced predators such as red foxes (Vulpes vulpes), and in doing so can benefit smaller native prey. It is possible that domestic dogs could perform similar ecological roles in some situations.

In some regions, dogs and their keen noses have been trained to help scientists find threatened species such as Tiger Quolls. Elsewhere they are helping to flush out and control feral cats.

An emerging and exciting conservation role for dogs is their growing use as “guardian animals” for wildlife, with the remarkable story of Oddball being the most well known.

Managing the problem

Dogs not only interact with wildlife, but can also attack and spread disease to humans, livestock and other domestic animals. As such, managing the problem requires looking at ecological, cultural and social perspectives.

Some of the regions with high numbers of species threatened by dogs are also hotspots for urbanisation and road building, which make it easier for dogs to access the habitats of threatened species. Urban development increases food waste, which feeds higher numbers of dogs. As dogs expand into new areas, the number of species they impact is likely to grow.

Street dogs scavenging food waste in India.
Achat1234/wikimedia

We can protect wildlife by integrating human health and animal welfare objectives into dog management. Vaccination and desexing campaigns can reduce disease risk and overpopulation problems. We should also focus on responsible dog ownership, removing dogs without owners, and reducing access to food waste.

Given the close relationship between humans and dogs, community engagement should form the basis of any management program. More research is needed to get a better picture of the scale of the problem, and of how dogs interact with other threats such as habitat loss. Such actions are critically important for ensuring the conservation of wildlife threatened by dogs around the world.


This article was co-authored by Dr Al Glen from Landcare Research, New Zealand and Dr Abi Vanak from the Ashoka Trust for Research in Ecology and the Environment, India. These institutions had no role in the design or funding of this research.

Tim Doherty, Research Fellow, Deakin University; Aaron J. Wirsing, Assistant Professor, School of Environmental and Forest Sciences, University of Washington; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Dale Nimmo, ARC DECRA Fellow, Charles Sturt University; Euan Ritchie, Senior Lecturer in Ecology, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University, and Thomas Newsome, Fulbright Scholar and Postdoctoral Research Fellow, Deakin University

This article was originally published on The Conversation. Read the original article.

Advertisements

Invasive predators are eating the world’s animals to extinction

Invasive species are a threat to wildlife across the globe – and invasive, predatory mammals are particularly damaging.

Our research, recently published in Proceedings of the National Academy of Sciences, shows that these predators – cats, rats and foxes, but also house mice, possums and many others – have contributed to around 60% of bird, mammal and reptile extinctions. The worst offenders are feral cats, contributing to over 60 extinctions.

So how can we stop these mammals eating away at our threatened wildlife?

Counting the cost

Our study revealed that invasive predators are implicated in 87 bird, 45 mammal and 10 reptile extinctions — 58% of these groups’ contemporary extinctions worldwide.

Invasive predators also threaten 596 species classed as vulnerable, endangered or critically endangered on the International Union for the Conservation of Nature Red List. Combined, the affected species include 400 birds, 189 mammals and 149 reptiles.

Twenty-three of the critically endangered species are classed as “possibly extinct”, so the number of extinctions above is likely to be an underestimate.

Until now, these shocking statistics have been unknown, and the heavy toll of invasive predators on native biodiversity grossly underappreciated. Species extinctions attributed to invasive predators include the Hawaiian rail (Zapornia sandwichensis) and Australia’s lesser bilby (Macrotis leucura).

Australia’s lesser bilby, now extinct.

Who are the worst offenders?

We found that three canids (including the red fox and feral dogs), seven members of the weasel family or mustelids (such as stoats), five rodents, two primates, two mongooses, two marsupials and nine species from other families negatively impact threatened species. Some of these species, such as hedgehogs and brushtail possums, don’t immediately spring to mind as predators, yet they are known to prey on many threatened species.

Feral cats threaten the most species overall (430), including 63 that have become extinct. This equates to one-quarter of all bird, mammal and reptile extinctions – making the feral cat arguably the most damaging invasive species for animal biodiversity worldwide.

Five species of introduced rodent collectively threaten 420 species, including 75 extinctions. While we didn’t separate out the impacts of individual rodent species, previous work shows that black rats (Rattus rattus) threaten the greatest number of species, followed by brown rats (R. norvegicus) and Pacific rats (R. exulans).

The humble house mouse (Mus musculus) is another interesting case. Despite their small size, house mice have been recorded eating live chicks of albatrosses, petrels and shearwaters.

Other predators that threaten large numbers of species are the domestic dog (Canis familiaris), pig (Sus scrofa), small Indian mongoose (Herpestes auropunctatus), red fox (Vulpes vulpes) and stoat (Mustela erminea).

Invasive mammalian predators (clockwise from top left): feral dog, house mouse, stoat, feral pig, feral cat, brushtail possum, black rat, small Indian mongoose and red fox (centre).
Clockwise from top-left: Andrey flickr CC BY 2.0 https://flic.kr/p/4M2E7y; Richard Adams flickr CC BY 2.0 https://flic.kr/p/7U19v9; Mark Kilner flickr CC BY-NC-SA 2.0 https://flic.kr/p/4D6LPe; CSIRO CC BY 3.0 http://www.scienceimage.csiro.au/image/1515; T. Doherty; Toby Hudson CC BY-SA 3.0 https://commons.wikimedia.org/wiki/File:BrushtailPossum.jpg; CSIRO CC BY 3.0 http://www.scienceimage.csiro.au/image/10564; J.M.Garg CC BY-SA 3.0 https://commons.wikimedia.org/wiki/File:Herpestes_edwardsii_at_Hyderaba.jpg; Harley Kingston CC BY 2.0 https://flic.kr/p/ceWFr7 (centre).

Island species most at risk

Species found only on islands (insular endemics) account for 81% of the threatened species at risk from predators.

The isolation of many islands and a lack of natural predators mean that insular species are often naive about new predators and lack appropriate defensive responses. This makes them highly vulnerable to being eaten and in turn suffering rapid population decline or, worse, extinction. The high extinction rates of ground-dwelling birds in Hawaii and New Zealand — both of which lack native mammalian predators — are well-known examples.

Accordingly, the regions where the predators threatened the greatest number of species were all dominated by islands – Central America and the Caribbean, islands of the Pacific, the Madagascar region, New Zealand and Hawaii.

Conversely, the continental regions of North and South America, Europe, Africa and Asia contain comparatively few species threatened by invasive predators. While Australia is a continent, it is also an island, where large numbers of native birds and mammals are threatened by cats and foxes.

Along with feral cats, red foxes have devastated native mammals in Australia.
Tom Rayner

Managing menacing mammals

Understanding and mitigating the impact of invasive mammal predators is essential for reducing the rate of global biodiversity loss.

Because most of the threatened species studied here live on islands, managing invasive predators on islands should be a global conservation priority. Invasive predators occur on hundreds of islands and predator control and eradication are costly exercises. Thus, it is important to prioritise island eradications based on feasibility, cost, likelihood of success and potential benefits.

On continents or large islands where eradications are difficult, other approaches are needed. This includes predator-proof fencing, top-predator restoration and conservation, lethal control, and maintenance of habitat structure.

Despite the shocking statistics we have revealed, there remain many unknowns. For example, only around 40% of reptile species have been assessed for the Red List, compared to 99% for birds and mammals. Very little is known about the impact of invasive predators on invertebrate species.

We expect that the number of species affected by invasive predators will climb as more knowledge becomes available.


This article was co-authored by Al Glen from Landcare Research, New Zealand. Landcare Research is a government-funded research organisation that conducts research into a range of conservation issues, including pest management. It did not provide funding for this research.

The Conversation

Tim Doherty, Research Fellow, Deakin University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Dale Nimmo, Lecturer in Ecology, Charles Sturt University, and Euan Ritchie, Senior Lecturer in Ecology, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University

This article was originally published on The Conversation. Read the original article.

Bushfires are pushing species towards extinction

Tim Doherty, Deakin University; Emma Burgess, The University of Queensland; Martine Maron, The University of Queensland, and Robert Davis, Edith Cowan University

Massive bushfires in recent months have tragically claimed people’s lives and destroyed their homes. These events are becoming more common as our warming and drying climate increases the frequency, intensity and extent of fires.

But these impacts aren’t just restricted to humans. Our native animals and plants are also affected by fire. Some species have even been pushed to the verge of extinction by the way fire patterns have changed. The International Union for the Conservation of Nature’s Red List identifies “fire and fire suppression” as a threat to more than 100 threatened species in Australia.

Recent bushfires in Victoria, Western Australia and Tasmania have all taken a devastating toll on threatened species and unique ecosystems.

Plant species threatened by fire (L to R): Andersonia pinaster, Athrotaxis cupressoides, and Banksia verticillataL to R: Sarah Barrett, brewbrooks/flickr (CC BY-SA 2.0, https://flic.kr/p/7g7BGb), Sarah Barrett

Burning biodiversity

Cape Arid National Park on WA’s south coast is home to the only known population of the critically endangered Western Ground Parrot. The parrot lives in unburned heathland, and its distribution has shrunk rapidly in recent decades.

Before last year’s fires, only 140 birds were thought to remain. Then in October and November a series of bushfires burned 90% of the species’ known habitat. It is not known how many birds may have survived the fires.

Also late last year, fires at Two People’s Bay Nature Reserve destroyed habitat of the critically endangered Gilbert’s Potoroo (the world’s rarest marsupial), as well as habitat of the threatened Noisy Scrub Bird, Western Bristlebird, Western Ringtail Possum, Quokka, and the plant Andersonia pinaster. Four populations of the rare Banksia verticillata were also burned in November at the nearby Torndirrup National Park.

These extreme fire events are also impacting species in southeastern Australia. In December, 2,500 hectares were burned in Victoria’s Otway Ranges. Native mammal populations in this region have been declining over recent decades, including that of the vulnerable New Holland Mouse. Such fires could worsen the outlook for these species, especially since foxes in the Otways are attracted to and increase their consumption of some mammals in recently burned areas.

The current burning of World Heritage forests in Tasmania is an equally concerning conservation catastrophe, and may be doing irreversible damage to these unique ecosystems.

Animal species threatened by fire (clockwise from top left): New Holland Mouse (Pseudomys novaehollandiae), Western Ground Parrot (Pezoporus flaviventris), Gilbert’s Potoroo (Potorous gilbertii), and Mallee Emu Wren (Stipiturus mallee).
Clockwise from top-left: Doug Beckers (flickr, CC BY-SA 2.0, https://flic.kr/p/6jpWxN), Alan Danks, Dick Walker and Gilbert’s Potoroo Action Group, Ron Knight (flickr, CC BY 2.0, https://flic.kr/p/diYjwY)

As part of its Threatened Species Strategy, the federal government has identified 20 threatened bird and 20 threatened mammal species for priority conservation action.

The list includes many species threatened by inappropriate fire regimes, such as Gilbert’s Potoroo, Western Ground Parrot, Mallee Emu Wren, South-eastern Red-tailed Black-Cockatoo, Western Ringtail Possum, Malleefowl, and Leadbeater’s Possum.

Halting extinction

But since these species evolved in a fire-prone environment, why is fire a problem for them now?

Not only are fires becoming more severe and frequent in parts of Australia, but for many species there is not much habitat left. Such species have already declined and are often reliant on habitat that hasn’t been burned for a long time, so a single fire can wipe out entire populations.

This creates complex ecological challenges for land managers and conservationists – especially where prescribed burning is used to reduce fire risk to people and their property.

Prescribed burning can be a valuable tool in protecting habitat from wildfire, but it must be science-based and carefully targeted. Until recently, Victoria had a policy to burn 5% of its land area every year, a practice that was threatening sensitive ecosystems and species, such as the endangered South-eastern Red-tailed Black Cockatoo. The recent lifting of the policy is therefore a major step away from arbitrary management targets and – hopefully – towards science-based conservation.

Other threats may have started the declines and made species more vulnerable to fire. These include habitat loss, disease and introduced predators.

Therefore, it is vital that conservation plans consider interactions between threats. When a species has only a handful of individuals remaining, captive breeding and the creation of insurance populations are sometimes necessary.

Climate change is expected to make fire patterns worse for wildlife in the future. We need political leadership on climate action if we are to understand and mitigate these impacts. Otherwise, we risk robbing future generations of the opportunity to see much of our amazing native wildlife that is currently threatened with extinction.

Only 1,500 South-eastern Red-tailed Black-Cockatoos remain, and too much fire is a major threat. © Bob McPherson

The authors acknowledge the Friends of the Western Ground Parrot Group, Gilbert’s Potoroo Action Group, and Sarah Barrett of the WA Department of Parks and Wildlife for photos and information.The Conversation

Tim Doherty, Research Fellow, Deakin University; Emma Burgess, Researcher, The University of Queensland; Martine Maron, Associate Professor of Environmental Management, The University of Queensland, and Robert Davis, Senior Lecturer in Vertebrate Biology, Edith Cowan University

This article was originally published on The Conversation. Read the original article.

Urban reptiles at risk from arsonists

Urban areas (i.e. towns, cities and their suburbs) contain around half of the world’s human population and Australia is one of the most urban countries on Earth, with 89% of Australians living in urban areas.

Percent of total population living in urban areas by countries. Source: http://kff.org/global-indicator/urban-population/#
Percent of total population living in urban areas by countries. Source: http://kff.org/global-indicator/urban-population/

The world’s population, and hence urban areas, are growing at an increasing rate globally and it is estimated that by 2030 urban land cover will increase by more than 1.2 million km2.

Urbanisation leads to large changes in the composition of native plant and animal communities and global estimates have found that urban areas retain on average only 8% of their original bird fauna and 25% of their plant species.

Native animal populations suffer from urbanisation due to habitat clearing and fragmentation, competition and predation from introduced species, and genetic effects that reduce population viability. Increased isolation of habitats and disrupted dispersal ability lead to an increased risk of local extinction from stochastic events such as fire or disease.

In this blog post I am going to give you a summary of some research Dr Rob Davis and I did on the response of an urban reptile community to fire and which was published in PLOS ONE earlier this year: Rapid Recovery of an Urban Remnant Reptile Community following Summer Wildfire.

The study location

My home town is Perth in Western Australia, which is a sprawling city of 2 million people stretching ~125 km up the coast. The original eucalypt and banksia woodlands in this area supported a rich reptile assemblage of 69 terrestrial species.

Land clearing for urban development has turned most of the original vegetation into many small remnants and a few larger ones nested in between the suburbs. You can get an idea of this by opening up the map below in a new window, switching to satellite view and zooming out.

One of these larger remnants is Kings Park which is located just 1 km from the CBD and covers 4.06 km2, making it arguably the biggest inner city park in the world. The park is managed by the Botanic Gardens and Parks Authority (BGPA).

 

Being an urban remnant, Kings Park experiences a number of environmental pressures, with weeds and fire (mostly caused by arson) being amongst the most important. In January 2009, a wildfire burnt 40 ha of bushland at the park, which provided a great opportunity to study the immediate post-fire dynamics of the reptile community.

The study

Partnering with the BGPA, Rob set up 10 pitfall trapping grids following the fire: five each in burnt and unburnt areas. Each grid consisted of nine pitfall traps in a 3×3 grid, along with five funnel traps. Starting in November 2009, we surveyed these grids every spring and autumn for five years to track how the reptile community was affected and recovered post-fire.

A pitfall trap containing a young bearded dragon Pogona minor. Credit: J Krawiec.
A pitfall trap containing a young bearded dragon Pogona minor. Credit: J Krawiec.
Over 19,600 trap-nights, we captured 1,541 reptiles from 19 different species. This included:
  • 11 skinks
  • 2 legless lizards
  • 2 elapid snakes and
  • 1 species each of geckoes, dragons, goannas and blind snakes.

Species richness in spring (mean±SE: 6.12±0.29) was double that in autumn (2.98±0.23). We used the spring data to examine how the reptile community recovered over the course of the study.

Patterns of recovery

Species richness at unburnt sites (dashed green line below) was higher than that at burnt sites (solid orange line) for the first three years post-fire, with no difference between the two in the final two years.

Screen Shot 2015-09-22 at 3.07.35 pm

 

 

 

 

 

Total reptile abundance at unburnt sites was higher than at burnt sites in the first two years following the fire, but was similar between burnt and unburnt sites after that. Conversely, species evenness at burnt sites was higher than unburnt sites for the first two years.

Screen Shot 2015-09-22 at 3.07.42 pm

 

Interestingly, we also found that individuals of the skink Ctenotus fallens captured in unburnt areas were larger than those captured in burnt areas for the first four years of the study.

Screen Shot 2015-09-23 at 6.11.35 pm

Ctenotus fallens. Credit: J Krawiec
Ctenotus fallens. Credit: J Krawiec

Rare species are at risk

Although reptile abundance, richness and evenness at burnt sites had converged with that of unburnt sites by the end of the study, there were a number of species that showed a clear preference for unburnt habitat (72-100% of all captures occurring at unburnt sites).

This includes species such as Burton’s legless lizard Lialis burtonis and the southern blind snake Ramphotyphlops australis. Since the park is subject to frequent fire as a result of arson, there is a risk that the proportion of unburnt areas will decrease to the determinant of these species.

Blind snake Ramphotyphlops australis. Credit: J Krawiec
Blind snake Ramphotyphlops australis. Credit: J Krawiec
Burton's legless lizad Lialis burtonis. Credit: J Krawiec
Burton’s legless lizard Lialis burtonis. Credit: J Krawiec

What next?

The question then remains: how many years of post-fire recovery does it take for the habitat to become optimal for these species? Based on the data at hand, we can say that five years is not long enough.

By continuing our monitoring at Kings Park into the future, we hope to answer this question and others. Long-term monitoring will also enable us to assess how the reptiles respond to the warming and drying climate that south-western Australia is currently experiencing.

You can read and download the paper for free at this link.

ICCB: fire ecology poster and award

Last week I returned from the International Congress for Conservation Biology (ICCB) in Montpellier, France. The conference was an outstanding event and I had a great time meeting old and new friends.

I presented a poster (below) which is an offshoot of my PhD and also a product of some research our group did on shrubland birds funded by the Gunduwa Regional Conservation Association. Our poster won the award for Best Student Presentation (Oceania Section), which I was very honoured to receive and say a big thank you to the SCB Oceania Section for the accolade. Also, a big congratulations goes to Jessica Walsh who won the award for Best Student Paper (Oceania Section), which you can read for free here.

Doherty ICCB_poster_ low res

 

Resources for research promotion and communication

Source: https://iidastudents.wordpress.com/2011/03/04/a-lesson-in-social-media-for-emerging-professionals/
Source: https://iidastudents.wordpress.com/

Today I was lucky enough to present at the InSPiRE conference in Perth, Western Australia. InSPiRE stands for Inter-University School Postgraduate Research Excellence. The conference is run by AWARE (Advancing Western Australian Research Education), which is a collaboration between the graduate research schools of WA’s five universities. InSPiRE runs over five days and was attended by more than 200 post-grad students from the five unis.

My talk was titled “Harnessing the power of both traditional and social media for research promotion“. In a nutshell, I discussed strategies for research promotion that include engagement with journalists, tips for interviews, using online news outlets (e.g. The Conversation) and the benefits of Twitter.

I have put together a list of resources that provide some really useful information on using different types of media for research communication. The scope is biased towards the sciences, but the information is relevant to all disciplines. The list isn’t exhaustive and I’m happy to add any extra resources you may know of if you’d like to leave a comment.

Traditional (‘old’) media

How to avoid being misquoted by journalists by Kevin Anselmo

Making an impact: How to deal with the media by Philip Cowley

Thoughts on academic scientists giving interviews by David Kroll

Pitch Perfect: Communicating with Traditional and Social Media for 9781579223335_cf200Scholars, Researchers, and Academic Leaders by William Tyson

How can scientists actively engage with the media? by Jacquelyn Gill @JacquelynGill

Social media

‘Feeling Better Connected’: Academics’ Use of Social Media by Deborah Lupton

Tips and Tricks: How to promote your research successfully online by Fran Davies (Altmetric)

An Introduction to Social Media for Scientists by Holly Bik and Miriam Goldstein

Science and Social Media: Some Academics Still Don’t ‘Get It’ by Kirk Englehardt9781843346814

Top 5 social media platforms for research development by Andy Miah @andymiah

Social Media for Academics, A Practical Guide by Diane Neal (ed.)

The A to Z of Social Media for Academia by Andy Miah

 

Twitter

Why I Tweet by Manu Saunders @ManuSaunders

How to live-tweet a conference: A guide for conference organizers and twitter users by David Shiffman @WhySharksMatter

Twitter: revolutionising scientific communication one hashtag at a time by Euan Ritchie @EuanRitchie1

Using Twitter to communicate conservation science beyond professional conferences by Sara Bombaci et al.

Killing cats, rats and foxes is no silver bullet for saving wildlife

Stoats (Mustela erminea), feral cats (Felis catus), red foxes (Vulpes vulpes) and black rats (Rattus rattus) are invasive predators in different parts of the world. Clockwise from top left: Sabec/commons.wikimedia.org (CC BY-SA 3.0); T Doherty; CSIRO/commons.wikimedia.org (CC BY 3.0); 0ystercatcher/Flickr (CC BY-NC-SA 2.0)

By Tim Doherty, Edith Cowan University; Chris Dickman, University of Sydney; Dale Nimmo, and Euan Ritchie, Deakin University

Cats, rats and foxes have wrought havoc on Australian wildlife and ecosystems. Known as “invasive mammalian predators”, these are species that have established populations outside their native range.

Responsible for numerous extinctions across the globe, this group of species also includes American mink in Europe, stoats and ferrets in New Zealand, and mongooses on many islands.

One common solution is to kill these predators. However, research published this week in the journal Biological Conservation shows it’s much more complicated than that. Killing invasive predators often doesn’t work and is sometimes actually worse for native wildlife.

Killing for conservation

Management of the threats to biodiversity posed by invasive predators has focused on reducing their populations using lethal control. This includes poison baiting, trapping and shooting.

These programs have at times been successful at local scales and on islands. However, they are extremely costly and they often fail to stop declines of native fauna at larger scales.

Such management programs often occur with little regard for how they might interact with other threats that are impacting ecosystems. This has led to unpredictable outcomes of invasive predator control. Sometimes it doesn’t work or, worse, it results in a negative outcome for wildlife.

Key disturbances

We identified six disturbances with strong potential to increase the impacts of invasive predators: fire, grazing by large herbivores, land clearing, altered prey populations, the decline of top predators and resource subsidies from humans (such as increased food or shelter availability).

Six key disturbances that interact with invasive predators, clockwise from top left: fire, altered prey populations, top-predator declines, resource subsidies, land clearing, and grazing by large herbivores. Clockwise from top left: CSIRO (CC BY 3.0); CSIRO (CC BY 3.0), T Doherty; T Doherty; endymion120 (Flickr, CC BY 2.0); USDA (public domain).

These disturbances interact with invasive predators in three main ways.

First, disturbances such as fire, grazing and land clearing result in a loss of vegetation cover, which makes prey more vulnerable to predation.

For example, small mammals in the Kimberley region of northern Western Australia experienced more predation by feral cats in an intensely burnt area, compared with patchily burnt and unburnt areas. Grazing by livestock similarly removes protective cover. Research shows that feral cats prefer to hunt in these areas because of the improved hunting success.

Second, increases in food or declines of competing top predators can allow populations of invasive predators to increase, thereby increasing their impact on native species.

For example, introduced prey species, such as rabbits in Australia, can support larger predator populations. This can lead to increased predation pressure on native species – a process termed “hyperpredation”.

The extinction of the Macquarie Island parakeet was attributed to this process. The parakeet co-existed with feral cats for more than 60 years, but declined rapidly to extinction following the introduction of rabbits to the island in 1879. Resource subsidies, such as garbage or hunters’ carcass dumps, can also support larger predator populations, leading to greater predation pressure.

Third, many of these disturbances also have a direct impact on native species, which is exacerbated by invasive predators. For example, habitat fragmentation reduces population sizes of many native species due to habitat loss. Increased predation by invasive predators can therefore make a bad situation much worse.

Getting it right

Our synthesis shows that management of invasive predators is likely to benefit from employing more integrated approaches.

Maintaining habitat complexity and refuges for prey species is one way that invasive predator impacts can be reduced. This includes improved management of fire and grazing. Lower-intensity fires that retain patchiness could reduce the predation-related impacts of fire on native species. Such approaches may be the best option where no effective predator control method exists, such as for cats in northern Australia.

Native top predators such as wolves in Europe and North America or dingoes in Australia can have suppressive effects on invasive predators. “Rewilding” is an option in some places where these species have declined. Where native predators conflict with livestock producers, guardian animals can often protect livestock from predation instead of lethal control.

Reducing resource subsidies is a simple way of reducing food resources for invasive predator populations.

If lethal control is used, it should be applied with caution. Selectively removing individual pest species from ecosystems can do more harm than good. Multi-species approaches are the best way to avoid such surprises and the order in which species are removed is an important consideration.

Rather than focusing on single processes, conservation managers should consider the multiple disturbances operating in stressed ecosystems and use management actions that address these threats in unison. Such integrated approaches are essential if further extinctions are to be avoided.

The paper is free to download until July 30 2015.

The ConversationThis article was originally published on The Conversation.
Read the original article.