Tag Archives: biodiversity conservation

Feral cats… they’re so un-Australian

By Tom Evans @thomgevans

Following my recent blog regarding the control of invasive alien species, I want to take a look at one particular animal that’s been receiving a great deal of media attention of late – the feral cat. According to the Australian Wildlife Conservancy (AWC), there are somewhere in the region of 20 million feral cats in Australia… and they kill about 75 million native Australian animals every night.


A feral cat and prey. Source: The State of Victoria

Extinction crisis

Australia has the worst rate of mammal extinctions on the planet, with 29 since European settlement. That’s about 10% of Australia’s original mammal fauna, including mice, bandicoots, potoroos, bettongs, rats, a wallaby and one of Australia’s only two bilby species – and marauding moggies are the principal culprits.

It is estimated that an individual feral cat kills an average of five animals every night – with some killing many more. Journalists in Australia recently published a controversial photograph showing a culled cat alongside the contents of its stomach (a vast array of dead animals). It’s a graphic image, but they argue that given the dire state of Australia’s wildlife, publishing the photo was justified. I’m inclined to agree – the image conveys an important message. You can access the article (and the photo) here (warning: graphic image).

The Action Plan for Australian Mammals, published earlier this year, represents the first comprehensive assessment of the conservation status of mammals across Australia – it identifies feral cats as the most significant threat to their survival. Furthermore, predation by feral cats is now listed as a key threatening process under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), which specifically identifies 35 bird species, 36 mammals, seven reptiles and three amphibians to which feral cats represent a specific threat. Evidence also suggests that feral cats are on the verge of causing a second wave of extinctions in Australia’s north – the nation’s sole remaining landscape reflecting Australian biodiversity prior to the arrival of Europeans.

You get the picture – one of only two continents in the world with no native cat species is now the world’s largest cattery.

Time is running out, but for whom?

It seems shameful that 20 million feral cats are still able to run riot in a relatively stable and wealthy country, which without doubt has the capacity to deal with the issue. So what’s being done about it?

Last Wednesday, the Federal Environment Minster, Greg Hunt, set out a plan to halt the loss of Australian mammals in Australia by 2020. At the centre of this plan is a pledge to eradicate all significant feral cat populations. Presumably this is because the Australian Government recognises that if it is going to make any progress towards meeting its 2020 biodiversity targets, signed up to under the Convention on Biological Diversity (CBD), then feral cats have to go. All hail the power of the multilateral agreement.


John Gould print image of the Pig-footed Bandicoot – a species extinction largely attributed to feral cat predation. Source: Museum of Victoria

This pledge has been met with a mixed response. Some describe Hunt as a hero, others question the Australian Government’s motivations, the likelihood of achieving the task, and in particular, the current proposals to use a poison bait called Curiosity. Hunt believes this approach “has the potential to make a real difference to the protection and recovery of our native species”. The bait contains a toxin that restricts the flow of oxygen in the bloodstream. Placed within a small piece of food, it is ‘less likely’ to be eaten by wild animals because unlike cats, they tend to nibble their food, resulting in rejection of the bait. However, tests have yet to demonstrate that this approach won’t harm other animals. It is curious then, that the success of the Australian Government’s strategy to eradicate feral cats relies quite heavily on the use of an unapproved poison bait.

Landscape management

In truth, there may be sites where a program of targeted baiting could be successful in reducing feral cat populations. However, it is unlikely to work in isolation. Australia is an enormous continent – baiting simply isn’t feasible. What’s needed is a range of techniques to deal with feral cats, including the broader management of Australia’s landscapes. The Victorian Government is currently progressing with plans to introduce the Tasmanian Devil into Wilsons Promontory National Park. The proposition here is that this top predator will compete with feral cats (and foxes) for food and nesting space, and may also take their young, reducing feral cat populations. Interestingly, Hunt recently acknowledged that he had not heard about the Victorian Government’s proposals, which perhaps suggests that Australia has yet to develop a coordinated national approach to deal with feral cats.

The cat-proof fence

Another approach that has proved successful in recent years is the establishment of a network of cat-proof enclosures. The AWC manages 23 properties, covering three million hectares of cat free land, with successful results for native species. One out of every five wild greater bilbys, and one of every three numbats now live within these enclosures. The AWC is currently constructing a 43 km fence to create the largest cat (and fox) free area on mainland Australia, with the aim being to reintroduce nine of Australia’s most endangered mammal species. The message here is that when feral cats are removed, wildlife bounces back.

I leave you with a final quote from the Chief Executive of the AWC, Atticus Flemming:

“…if we remove feral cats from the landscape, we will see massive increases in the numbers of native animals… You wander at night through those areas where we’ve eradicated feral cats, and it’s like stepping back 200 years. The bush is alive. There are bilbys everywhere, bettongs everywhere, bridled nailtail wallabies. The ground is moving with little animals. That is what the bush must have been like before there were foxes and cats.”

Sounds purrfect to me.

Tom Evans
PhD Candidate – The London NERC DTP
University College London
Twitter: @thomgevans
Research Gate: https://www.researchgate.net/profile/Thomas_Evans6


Invasive alien species

By Tom Evans @thomgevans

The aliens have landed. They’ve taken up residence in our waterways, our cities, our farmland and forests. Their negative impacts to both the environment and the economy are enormous, and they aren’t going home any time soon. So what are ‘alien species’? In short, they are animals, plants or other organisms that we have introduced to areas outside of their natural range. They are considered to be ‘invasive’ when they become established, disperse and have negative impacts on people and/or wildlife.

Free oyster cards

Pretty much every habitat across the globe has been invaded by alien species – and the inalienable fact is, we put them there. The world is getting smaller – with improvements to transport by air, land and sea, international travel and trade have increased dramatically. As a result, species that wouldn’t otherwise have the opportunity to travel (mussels don’t have feet – well actually they have a foot, but it’s not made for walking long distances) are hitching a ride across the globe.

Alien species have been introduced to new surroundings both intentionally and unwittingly. The unrelenting frogmarch of the cane toad along the eastern seaboard of Australia, much to the detriment of large predator populations (think quolls, snakes, lizards and goannas) is an example of a deliberate introduction with significant environmental consequences. The Shine Lab at Sydney University has been working to contain the toad invasion for many years.

A death adder killed by a cane toad. Source: canetoadsinoz.com.

A death adder killed by a cane toad. Source: canetoadsinoz.com.

The zebra mussel’s grip on the Great Lakes, where it clogs water supply infrastructure and outcompetes native species, reducing the food supply for important commercial fish species, is an example of an accidental introduction with disastrous environmental, recreational and economic impacts. In this case, the tenacious mollusc was transported to North America in the ballast water of ships embarking from ports in Western Europe. The Centre for Invasive Species Research (CISR) at the University of California, Riverside (UCR), recently estimated that costs to control zebra and quagga mussels in the Great Lakes amount to $500 million/year.

Zebra mussels smothering a current meter (Lake Michigan). Source: National Oceanic and Atmospheric Administration (NOAA).

Zebra mussels smothering a current meter (Lake Michigan). Source: National Oceanic and Atmospheric Administration (NOAA).

Ponto-Caspian catastrophe?

The UK has not escaped the impacts of invasive alien species. Earlier this month, the quagga mussel was found in the UK for the first time. Prior to this unwelcome discovery, the quagga mussel was identified by scientists at the Centre for Ecology and Hydrology (CEH) as the single greatest threat to British wildlife of all alien species. Equally alarming is this month’s revelation that the threat of invasion by the quagga mussel, along with several other species from the Ponto-Caspian region (that’s Southeast Europe to you and me) is now so real that parts of Great Britain face the grim prospect of invasional meltdown1.

Evicting toad from Toad Hall

Last month, in recognition of the ever growing threat posed by potential invasions such as the quagga mussel, along with the lack of a coherent EU wide strategy to address invasive alien species, and the mounting costs associated with their containment and management (recently estimated to be €12 billion/year in Europe) (http://www.eea.europa.eu/highlights/invasive-alien-species-a-growing), the EU adopted a new regulation on invasive alien species (http://ec.europa.eu/environment/nature/invasivealien/index_en.htm). This legislation requires Member States to develop a list of species of Union concern, informed by risk assessments for individual species. It therefore encourages a cross-border approach to a cross-border problem – something that has been lacking to date. The regulation will be published in the Official Journal of the European Union in the coming weeks.

Instructions to boaters at Lake Mead, Nevada to prevent quagga mussel transportation. Source: JN Stuart. (CC BY-NC-ND 2.0).

Instructions to boaters at Lake Mead, Nevada to prevent quagga mussel transportation. Source: JN Stuart. (CC BY-NC-ND 2.0).

A number of recent research initiatives within the field of invasion biology aim to compliment and inform the above process. A protocol for scoring the impacts of invasive species has recently been developed2 and refined3, enabling the severity of a suite of environmental, economic and social impacts associated with a species to be calculated, informing risk assessments for potential invasions. Studies have shown that this methodology can be effectively applied to different taxonomic groups4 (see also Kumschick et al. In press5), and can also be used to inform studies that aim to predict the impacts of a species prior to invasion6.

This scoring methodology is also integral to a proposal to develop a global list of alien species classified by their environmental impacts7 that aligns with the existing IUCN Red List of Threatened Species (which is celebrating its 50th birthday in 2014, having become a global reference tool for biodiversity). The development of a standardised approach to quantify and compare the impacts of alien species will help us to predict whether potential invaders are likely to have negative impacts in their new range. This is important, as it allows for early intervention to prevent the establishment of alien species, and enables us to efficiently allocate money and resources where they are most needed to prevent or contain an emerging invasion.

Tom Evans
PhD Candidate – The London NERC DTP
University College London
Twitter: @thomgevans
Research Gate: https://www.researchgate.net/profile/Thomas_Evans6


  1. Gallardo B, Aldridge DC (2014) Is Great Britain heading for a Ponto–Caspian invasional meltdown? Journal of Applied Ecology. doi: 10.1111/1365-2664.12348.
  2. Nentwig W, Kühnel E, Bacher S (2010) A generic impact-scoring system applied to alien mammals in Europe. Conservation Biology 24: 302–311. doi: 10.1111/j.1523-1739.2009.01289.x
  3. Kumschick S, Nentwig W (2010) Some alien birds have as severe an impact as the most effectual alien mammals in Europe. Biological Conservation 143 (2010) 2757–2762.
  4. Kumschick S, Bacher S, Blackburn TM (2013) What determines the impact of alien birds and mammals in Europe? Biological Invasions 15: 785–797.
  5. Kumschick S et al. (In press) Comparing impacts of invasive plants and animals using a standard scoring system.
  6. Evans T et al. (2014) Comparing determinants of alien bird impacts across two continents: implications for risk assessment and management. Ecology and Evolution 2014; 4(14): 2957–2967.
  7. Blackburn T et al. (2014). A unified classification of alien species based on the magnitude of their environmental impacts. PLoS Biology 12(5): e1001850. doi:10.1371/journal.pbio.1001850.