Tag Archives: feral cats

For whom the bell tolls: cats kill more than a million Australian birds every day

The Conversation

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On the prowl in the outback. Hugh McGregor/Arid Recovery, Author provided

John Woinarski, Charles Darwin University; Brett Murphy, Charles Darwin University; Leigh-Ann Woolley, Charles Darwin University; Sarah Legge, Australian National University; Stephen Garnett, Charles Darwin University, and Tim Doherty, Deakin University

Cats kill more than a million birds every day across Australia, according to our new estimate – the first robust attempt to quantify the problem on a nationwide scale.

By combining data on the cat population, hunting rates and spatial distribution, we calculate that they kill 377 million birds a year. Rates are highest in Australia’s dry interior, suggesting that feral cats pose a serious and largely unseen threat to native bird species.


Read more: Ferals, strays, pets: how to control the cats that are eating our wildlife


This has been a contentious issue for more than 100 years, since the spread of feral cats encompassed the entire Australian mainland. In 1906 the ornithologist A.J. Campbell noted that the arrival of feral cats in a location often immediately preceded the decline of many native bird species, and he campaigned vigorously for action:

Undoubtedly, if many of our highly interesting and beautiful birds, especially ground-loving species, are to be preserved from total extinction, we must as a bird-lovers’ union, at no distant date face squarely a wildcat destruction scheme.

His call produced little response, and there has been no successful and enduring reduction in cat numbers since. Nor, until now, has there been a concerted effort to find out exactly how many birds are being killed by cats.

Counting the cost

To provide a first national assessment of the toll taken by cats on Australian birds, we have compiled almost 100 studies detailing the diets of Australia’s feral cats. The results show that the average feral cat eats about two birds every five days.

We then combined these statistics with information about the population density of feral cats, to create a map of the estimated rates of birds killed by cats throughout Australia.

Number of birds eaten per square kilometre. Brett Murphy, Author provided

We conclude that, on average, feral cats in Australia’s largely natural landscapes kill 272 million birds per year. Bird-kill rates are highest in arid Australia (up to 330 birds per square km per year) and on islands, where rates can vary greatly depending on size.

We also estimate (albeit with fewer data) that feral cats in human-modified landscapes, such as the areas surrounding cities, kill a further 44 million birds each year. Pet cats, meanwhile, kill about 61 million birds per year.

Overall, this amounts to more than 377 million birds killed by cats per year in Australia – more than a million every day.

Which species are suffering?

In a related study, we also compiled records of the bird species being killed by cats in Australia. We found records of cats killing more than 330 native bird species – about half of all Australia’s resident bird species. In natural and remote landscapes, 99% of the cat-killed birds are native species. Our results also show that cats are known to kill 71 of Australia’s 117 threatened bird species.

Birds that feed or nest on the ground, live on islands, and are medium-sized (60-300g) are most likely to be killed by cats.

Galahs are among the many native species being killed by feral cats. Mark Marathon, Author provided

It is difficult to put a million-plus daily bird deaths in context without a reliable estimate of the total number of birds in Australia. But our coarse assessment from many published estimates of local bird density suggests that there are about 11 billion land birds in Australia, suggesting that cats kill about 3-4% of Australia’s birds each year.

However, particular species are hit much harder than others, and the population viability of some species (such as quail-thrushes, button-quails and ground-feeding pigeons and doves) is likely to be especially threatened.

Our tally of bird deaths is comparable to similar estimates for other countries. Our figure is lower than a recent estimate for the United States, and slightly higher than in Canada. Overall, bird killings by cats seem to greatly outnumber those caused by humans.

In Australia, cats are likely to significantly increase the extinction risk faced by some bird species. In many locations, birds face a range of interacting threats, with cat abundance and hunting success shown to increase in fragmented bushland, in areas with high stocking rates, and in places with poorly managed fire regimes, so cat impacts compound these other threats.

Belling the cat

What can be done to reduce the impact? The federal government’s Threatened Species Strategy recognises the threat posed by feral cats, albeit mainly on the basis of their role in mammal extinctions.

The threatened species strategy also prioritised efforts to control feral cats more intensively, eradicate them from islands with important biodiversity values, and to expand a national network of fenced areas that excludes feral cats and foxes.

But while fences can create important havens for many threatened mammals, they are much less effective for protecting birds. To save birds, cats will need to be controlled on a much broader scale.


Read more: The war on feral cats will need many different weapons


We should also remember that this is not just a remote bush problem. Roughly half of Australia’s cats are pets, and they also take a considerable toll on wildlife.

While recognising the many benefits of pet ownership, we should also work to reduce the detrimental impacts. Fortunately, there is increasing public awareness of the benefits of not letting pet cats roam freely. With such measures, cat owners can help to look after the birds in their own backyards, and hence contribute to conserving Australia’s unique wildlife.


The ConversationWe acknowledge the contribution of Russell Palmer (WA Department of Biodiversity Conservation and Attractions), Chris Dickman (University of Sydney), David Paton (University of Adelaide), Alex Nankivell (Nature Foundation SA Inc.), Mike Lawes (University of KwaZulu-Natal), and Glenn Edwards (Department of Environment and Natural Resources) to this article.

John Woinarski, Professor (conservation biology), Charles Darwin University; Brett Murphy, Senior Research Fellow, Charles Darwin University; Leigh-Ann Woolley, Research Associate, Charles Darwin University; Sarah Legge, Associate Professor, Australian National University; Stephen Garnett, Professor of Conservation and Sustainable Livelihoods, Charles Darwin University, and Tim Doherty, Research Fellow, Deakin University

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.

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Eastern quolls edge closer to extinction – but it’s not too late to save them

The Conversation

Bronwyn Fancourt, University of Tasmania

Eastern quolls – small, fleet-footed and ferocious – are one of Australia’s few surviving marsupial predators. They were once so common in southeast Australia that when Europeans arrived the quolls were reportedly hyperabundant.

But by the 1960s they were extinct on the mainland, driven down by a combination of disease, poisoning, persecution and predation.

Despite their mainland demise, eastern quolls continued to thrive in Tasmania – until recently. Across Tasmania, quoll numbers declined by more than 50% in the 10 years to 2009 and show no sign of recovery.

Recognising this worrying decline, the quolls have recently been listed as endangered internationally and in Australia. This is a stark reminder of how quickly a common species can plunge towards extinction.

But the quolls can still recover, as long as we act now while we still have an opportunity. In research published in Wildlife Research, I looked at what caused the decline, and how we can help.

Change in the weather

Several factors coincided with the decline, but after five years of investigation I found that a period of unfavourable weather was the most likely explanation.

Eastern quolls prefer areas with low rainfall and cold winters. But an 18-month period of warm winters and higher seasonal rainfall during 2002-03 resulted in most of Tasmania becoming unsuitable for eastern quolls. This rapidly drove their numbers down. In fact, the amount of environmentally suitable habitat in this period was lower than at any other time during the previous 60 years.

With the frequency of extreme weather events predicted to increase over coming decades, the future for eastern quolls looks uncertain.

Eastern quoll numbers declined as unfavourable weather conditions reduced the amount of environmentally suitable habitat across Tasmania (grey shading). Fancourt et al (2015)

The predator pit

Interestingly, while weather conditions have since improved, eastern quolls have not recovered. With their numbers pushed so low, the remaining small populations can no longer breed faster than other threats kill them off. Historically, when quoll numbers were higher, they could cope with these threats.

Quolls are now trapped in what ecologists call a “predator pit”. Predators, cars, poison and a range of other threats are killing quolls as quickly as they can reproduce.

So population growth is in limbo – not because any threats have increased, but because small populations don’t have the capacity to outpace those same threats anymore.

Contrary to earlier predictions, feral cat numbers in Tasmania have not increased following declines in the Tasmanian devil population. Quoll populations could previously cope with the loss of a few quolls (mainly juveniles) to cats. However, that same number of quolls killed by cats is now potentially enough to wipe out any population growth, preventing the species’ recovery.

While feral cat numbers have not increased in Tasmania, cat predation of juvenile quolls could still be preventing their population from recovering. Bronwyn Fancourt

Numbers game

The key factor preventing quoll recovery is their current small population. Quoll numbers need a boost, increasing reproductive capacity so that they can once again outpace the threats they are facing. This could be done by supplementing small, surviving populations in Tasmanian with quolls from captive-breeding colonies, insurance populations or the wild population on Bruny Island (which is doing better than mainland Tasmania).

Reducing feral cat numbers at key sites in early summer could also help reduce predation as juvenile quolls enter the population. That would potentially increase juvenile survival and allow quoll populations to grow and recover.

Increasing survival rates of juvenile quolls in the wild is key to helping the species recover. Bronwyn Fancourt

Should quolls be reintroduced to the mainland?

Since word of the eastern quolls’ plight has spread, there has been increasing talk of reintroducing them to Australia’s mainland, where they disappeared more than 50 years ago. Such proposals are often well-intentioned and could potentially help restore some mainland ecosystems.

However, this could actually serve to drive wild populations in Tasmania closer to extinction, making the species’ recovery more difficult.

With only small populations persisting in the wild, removing only one or two individuals from a population could be enough to render that population functionally extinct – and once a population is functionally extinct it is on the path to total extinction.

Similarly, using quolls from captive colonies and insurance populations for mainland reintroductions further removes valuable quolls that could be used to repopulate and recover wild populations in Tasmania.

The eastern quoll’s persistence in Tasmania decades after it disappeared from the mainland suggests Tasmania is a far safer place for eastern quolls and offers them the best chance to recover. Removing them from a relatively safe place and reintroducing them to high-risk mainland sites filled with dingoes, foxes and toxic fox baits could actually hinder, not help, their recovery. For example, while baiting foxes may reduce the threat from foxes, it takes less than half of one fox bait to kill an adult female eastern quoll.

Mainland reintroductions should definitely be a goal in the longer term. But given the dangerously low numbers in Tasmania, we shouldn’t take Tasmanian quolls for high-risk mainland reintroductions until the Tasmanian population is safe. Once numbers in the wild have recovered, wild-sourced Tasmanian quolls could be reintroduced to mainland sites without putting wild populations at risk.

It’s time to act

Australia’s declining species face a slippery slope towards extinction. The key to recovery is understanding why the species declined, then acting while there is still time.

Australia’s history is littered with examples where delays and inaction prevented small populations from recovering, with some species now lost forever. The eastern quolls’ fate is not yet sealed. But we have to act now.

The ConversationBronwyn Fancourt, Honorary Research Associate, University of Tasmania

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.
 

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Invasive predators are eating the world’s animals to extinction – and the worst is close to home

The Conversation

Tim Doherty, Deakin University; Chris Dickman, University of Sydney; Dale Nimmo, Charles Sturt University, and Euan Ritchie, Deakin University

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.

The ConversationTim 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. (Reblogged by permission). Read the original article.
 

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The war on feral cats will need many different weapons

The Conversation

Katherine Moseby and John Read

At the Threatened Species Summit last week in Melbourne, Environment Minister Greg Hunt and Threatened Species Commissioner Gregory Andrews declared war on feral cats.

Cats are thought to be a significant contributor to the decline of many threatened species.

Targets in the released threatened species strategy include culling two million cats by 2020, creating new safe havens for threatened species (cat-free islands and sanctuaries), restoring habitat and emergency intervention for our most critically endangered species.

Excluding cats using fencing is an increasingly important tool used to protect threatened species. New exclusion fencing projects received significant funding under the latest strategy.

One of us (Katherine) was lucky enough to be asked to give a presentation at the summit on alternative methods of controlling feral cats. The following article summarises this presentation and highlights the importance of investing in a broad range of cat control methods.

Cats are highly adaptable and highly variable, hence we must continue to search for their Achilles Heel and invest in a wide range of control methods.

Poison baiting

Widespread poison baiting for cats has come a long way in the last few decades with baits such as Eradicat, Curiosity and a new hybrid Eradicat bait being produced.

These baits were developed after years of research conducted initially by the WA Department of Parks and Wildlife and are a soft meat sausage injected with 1080 poison or containing an encapsulated PAPP (Para-aminopropiophenone) pill. These baits have had most success in island eradications and areas where alternative prey are scarce.

In order to kill a cat using poison baits, cats must first find and then ingest the bait.

Unfortunately, cats hunt mainly using sight and sound so finding an inert sausage is a challenge for a cat.

Large numbers of baits must be laid, the usual density is 50 per square km, 10 times higher than the recommended fox baiting density of 5 per square km.

Despite this, many cats fail to find a poison bait before they break down and are no longer toxic. Even when cats do find baits, up to 80% of encounters do not lead to bait ingestion, with cats often ignoring, sniffing or avoiding baits when detected. This is because cats prefer to catch their own prey and will only ingest a bait when hungry.

Non-target uptake can also be high – species such as crows, goannas and quolls can take more than half of laid baits in some instances.

Successful baiting relies on using large densities of baits in areas with low food availability at the right time of year when cats are hungriest. Practitioners are continuing to develop ways of improving bait uptake and several important baiting programs received funding under the Threatened Species Strategy.

Grooming traps

A recent invention removes the need for cats to be hungry to ingest poison. An automated grooming trap squirts a poisonous paste onto the fur of the cat as it walks past a trap station, which it then ingests through compulsive grooming.

Cats are fastidious groomers and pen trials have found 9 out of 10 cats will ingest the paste when it is squirted on their fur. The trap uses an array of sensors to restrict triggering to target species and is currently being developed for field trials around Australia. The grooming traps have a silent activation, can store up to 20 doses and can sit unattended for months at a time.

Although unlikely to be used in broadscale applications, the grooming trap may be critical for protecting small threatened species populations and reducing the impacts of cats in areas where food availability is high.

The grooming trap received much needed funding for further development at the Threatened Species Summit.

Get rid of rabbits, get rid of cats

Widespread indirect methods of reducing cat impacts are also important. Recent work has found that the Rabbit Haemorrhagic Virus Disease (RHVD) (otherwise known as Rabbit Calicivirus) released in 1995 has had a significant positive impact on many desert threatened mammal species.

The range of species such as the Plains Mouse, Dusky Hopping Mouse and Crest-tailed Mulgara has increased by as much as 70 fold in the last 20 years due largely to reduced predation.

RHDV reduced rabbit abundance by up to 95% in the arid zone of Australia which resulted in a natural steep decline in feral cats and foxes, the main predator of rabbits in that region.

The increase in vegetation cover coupled with a massive decline in predation pressure has allowed these native rodents and marsupials to recover.

This would undoubtedly be one of the most significant recoveries of threatened species in Australia. RHVD was relatively cheap, for an initial investment of only $12 million. The agricultural benefit alone totalled more than A$6 billion and the benefits to threatened species have been dramatic but remain unquantified.

Other researchers have also found that by manipulating fire and stock grazing pressure, broadscale indirect benefits can be achieved for threatened species through a reduction in susceptibility to cat predation.

These indirect benefits include making it more difficult for cats to hunt by increasing ground cover, and increasing the productivity of the landscape thereby allowing native species to increase their reproductive output and tolerate higher predation pressure.

Serial cats

All cats are not created equal and recent work in the Flinders Ranges National Park has highlighted the impact of catastrophic cats on reintroduction programs. The reintroduction of the western quoll resulted in nearly a third of the quolls being killed by feral cats.

A quoll killed by a feral cat in the Flinders Ranges, South Australia. Melissa Jensen, Author provided

DNA analysis indicated that quolls were killed by large male cats with most cats responsible for multiple kills (Moseby, Peacock and Read,in press,Biological Conservation). These specialist hunters could be targeted by making their prey toxic, in other words employing toxic Trojans (poison capsules implanted under the skin of prey species where they remain stable) to control specialist cats.

Poison capsules can be implanted under the skin of prey species where they remain stable. If a cat kills and ingests a toxic Trojan, the capsule will break down in the acidic environment of the cat’s stomach releasing the poison and preventing it from killing more individuals. Research is continuing into this poison delivery device which may result in improved targeted cat control.

Get smart

Finally, an ARC linkage grant between the University of New South Wales and Arid Recovery is researching ways to improve the anti-predator behaviour of threatened species.

Our native species did not evolve with introduced cats and foxes and hence may exhibit inappropriate or ineffective anti-predator responses. This prey naivety can lead to high susceptibility even to low levels of exotic predators.

Containing our threatened species on off-shore islands or behind fences is potentially exacerbating the issue as they are not exposed to mammalian predators and can develop “island syndrome” where they fail to recognise predators as dangerous.

The project involves trialling “in situ” predator training where low levels of predators are added to populations of threatened species for extended periods to improve their anti-predator behaviour.

The theory is that natural selection and learning will lead to improved survival and behaviour of successive generations of threatened species.

Whilst this may be a long term endeavour, ways of facilitating co-existence and increasing the resilience of our native species to exotic predators are urgently needed as it is likely that the wily feral cat is here to stay.

The authors would like to acknowledge the following for contributions. Poison Baits – Dave Algar, Michael Johnston, Keith Morris; Grooming traps- Invasive Animals CRC; Broadscale indirect methods – Reece Pedler, Peter Bird, Rob Brandle Rick Southgate, Rachel Paltridge, Sarah Legge; Specialist Hunters – Dave Peacock; Improving Prey Responses – Mike Letnic, Dan Blumstein, Bec West. Ecological Horizons has received funding from Sporting Shooters, FAME, Bush Heritage and SA and Australian Govt for development of Feral Cat Grooming Traps.

The ConversationKatherine Moseby is Associate Lecturer, Ecological and Environmental Sciences at University of AdelaideJohn Read is Associate Lecturer, Ecology and Environmental Sciences at University of Adelaide.

This article was originally published on The Conversation. (Reblogged by permission). Read the original article.


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