A numbers game: killing rabbits to conserve native mammals



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Controlling rabbit populations has a key role in conserving Australia’s native plants and animals
William Booth

Euan Ritchie, Deakin University; Damien Fordham, University of Adelaide, and Miguel Lurgi, Centre national de la recherche scientifique (CNRS)

Invasive species have a devastating effect on biodiversity. In Australia, introduced red foxes and feral cats have been implicated in the majority of the extinctions of the native mammal fauna, which has been decimated since European arrival.

But there’s a herbivore that also causes eco-catastrophe. Rabbits both compete with native animals for food and shelter and act as easy prey for abundant populations of cats and foxes. By over-grazing vegetation and reducing habitat complexity, they make hunting easier for introduced predators.




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


Food webs are complex. Because of this, once an invasive species is embedded in a food web, simply eradicating them without considering the potential knock-on effects to other species they interact with, could cause unintended and undesirable consequences. We modelled different rates of rabbit population reduction to assess what level of control might be best for aiding the conservation of native mammals and not causing negative outcomes.

Rabbit numbers boom and crash

Rabbits, famously, reproduce rapidly and can cope with a relatively high predation rate. This can cause “hyper-predation”, where rabbit-inflated cat and fox populations indirectly increase the predation pressure on native mammals. This is especially so when rabbit populations intermittently crash due to, for example, extreme environmental events (like severe and prolonged droughts) or disease. This causes predators to switch their diet and eat more native mammals.

Threatened species such as the greater bilby are likely to benefit from rabbit control.
Jasmine Vink

This logically suggests that reducing rabbit numbers might thus help reduce cat and fox populations, by removing their abundant prey. Collectively this should benefit native plants and animals, including many threatened mammal species. However, ecosystem and pest management is a complex game.

When controlling rabbits we need to look beyond one or two species. We should consider the potential consequences for the entire ecological community, which ultimately depend on how changes in one species percolate through the network of ecological interactions between them.

Our new research, recently published in the Journal of Applied Ecology, set out to examine these questions in more detail. We consider other key players in Australia’s arid regions, such as kangaroos and dingoes, when looking at the effects of rabbit control on small native mammals. Our aim was to provide a better understanding of how changes in rabbit populations might affect other species via the food web.

We developed a multi-species ecological network model to describe and quantify how changing rabbit abundance can affect species on different feeding levels. In addition to rabbits, small native mammals, and mesopredators (cats and foxes), our model also considers apex predators (dingo) and large herbivores (kangaroo) as part of the Australian arid food web. This model allowed us to examine changes in predator-prey interactions (including potential prey switching and hyper-predation) and how these could affect the survival of native prey through time.

Our model of an Australian arid ecosystem food web.
Author provided

We found that removing rabbits at rates between 30-40% appeared to benefit small mammals. This is approximately the rate at which rabbits are currently managed in Australia using biocontrol agents (introduced diseases).

Rabbit control in Australia typically involves a “press and pulse” approach. Rabbit populations are suppressed via biocontrol (press) and periods of warren destruction and poisoning (pulse). Finding that reducing rabbit populations by around 40% seems most beneficial to small mammals is important, as it informs how and when we combine these strategies.

The 40% rate corresponds well with the disease-induced (press) mortality rate in rabbit populations due to rabbit haemorrhagic disease and myxomatosis. These are the primary biocontrol agents used in arid Australia to control rabbit populations.

Our study supports rabbit-reduction strategies that involve sustained “press” control, that kill a moderate portion of a rabbit population, with less frequent removal at higher proportions of the population.

To effectively manage invasive species, it’s important to focus on entire communities. Targeting single species might not be enough – every animal exists within a complex web of interactions.




Read more:
Mourn our lost mammals, while helping the survivors battle back


There has been much focus by the current government on controlling feral cats, as a way to conserve many of Australia’s unique and threatened mammal species.

The ConversationHowever, more focus could be devoted to protecting habitat cover and complexity, by reducing the land clearing and over-grazing that makes hunting easier. We can also manage rabbits sensibly to reduce competition for resources, and indirectly control cats and foxes.

Euan Ritchie, Associate Professor in Wildlife Ecology and Conservation, Centre for Integrative Ecology, School of Life & Environmental Sciences, Deakin University; Damien Fordham, , University of Adelaide, and Miguel Lurgi, Postdoctoral research fellow, Centre national de la recherche scientifique (CNRS)

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

The good, the bad and the ugly: research funding flows to big and beautiful mammals in Australia


Susan Lawler, La Trobe University

You might think that scientists are rational, logical creatures, but it turns out we are biased and lazy. A recent publication by Trish Fleming and Phil Bateman in Mammal Review has analysed how research on Australian mammals is distributed, and the results are not pretty.

What is being reported in the media is that ugly animals are at greater risk of extinction because research funding is more often directed towards species that are considered cute and cuddly. Having read their publication, I will argue this is not entirely true, but the researchers did find that Australian mammals fell into three broad categories that they called the good, the bad and the ugly.

The researchers used a tool called a species h-index: basically they compared research on various species by assessing how often they are mentioned in publications and how often those papers were cited by other scientists.

The Good: Monotremes and marsupials

Australia is well known for its unusual and unique mammalian fauna, and of course the stars of the show either lay eggs or have pouches. Echidnas and platypus are of great interest biologically because they are the only extant monotremes: they lay eggs and feed their babies with milk. There is nothing like them anywhere else on the planet, so it makes sense that even though they are only 0.6% of the mammal species in Australia, they are in 4% of publications.

Our native marsupials are also well researched. Kangaroos, koalas, Tasmanian devils, possums and their relatives constitute 49% of Australian mammals. They are also well researched, as they are in 73% of the publications assessed.

The Bad: Introduced eutherians

Eutherians are the placental mammals like ourselves. No pouches, no eggs, and relatively common outside of Australia. Most of our feral pests fall into this category and they attract a lot of research interest and funding because of their disproportionate economic impacts. Rabbits, house mice, foxes, cats and deer fall into the category of “bad” mammals. They represent 6% of mammal species in Australia and are mentioned in 12% of the publications.

Controversially, the authors decided to categorise the dingo as an introduced mammal, even though many of us consider it to be an important component of a healthy ecosystem. Other research shows that when dingo numbers are healthy, foxes and cats have less of an impact on small native mammals.

The Ugly: Native eutherians

Many people do not realise that we have a large number of native mammals that are not marsupials. These species found their way to our continent millions of years ago and have adapted to conditions here. Unfortunately, these are the rodents and bats, which have a bad reputation even though in most cases they are not interested in infesting your home or your hair.

The native eutherians represent no less than 45% of Australian mammals, but they are only in 11% of publications, which is less than the introduced ferals. The researchers put them in the “ugly” category despite the fact that many of these are quite cute.

For example, we keep Mitchell’s hopping mice as pets and I can assure you that they are adorable. Everyone who is lucky enough to visit after dark (they are nocturnal so only come out at night) has agreed. They jump, they play, they have personalities. So nobody is going to convince me that they belong in the ugly category.

What they are is small and cryptic. Given the difficulty of finding them in their cage during the day, I can only imagine how difficult it would be to observe them in the wild. Bats are even more difficult as their sleeping quarters are high up in trees or deep in rocky crevices.

Most research on big animals with large ranges

Unsurprisingly, given the challenges, the animals that attract the most research attention are large and are distributed over a large geographic range. This may be in part because these are the species that are of more interest to the public and therefore attract more funding, but it also makes scientists look lazy.

It is far easier to survey koalas than it is to survey microbats, but when we consider that the microbats are eating insects for us, while koalas are more likely to kill trees, there may be good reason to shift our focus. (By the way, you can build a microbat roosting box to attract them to your house, see here).

Where should the funding go?

Of most concern is that there was no correlation between a species’ IUCN status (endangered, threatened, etc.) and the amount of research interest. Given the large number of species that are data deficient, this means that vulnerable species are not getting enough attention.

Australia has suffered the greatest loss of native mammals globally and many of us want that to change. Unfortunately, good intentions are not enough. We need research funding, and this is not evenly distributed. Australia belongs to the 40 most underfunded countries for conservation. One researcher has suggested the shortfall is over $350 million AUD, and yet we do not receive international biodiversity funding aid.

Here’s hoping the ugly mammals of Australia are not made to suffer the ultimate fate of extinction, just because we are unable to take a step back and set priorities based on evidence rather than emotion.

Perhaps we need to start an Ugly Animal Preservation Society, like they have in the UK.

The Conversation

Susan Lawler, Senior Lecturer, Department of Ecology, Environment and Evolution, La Trobe University

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

Australia: Saving Australia’s Threatened Mammals


The link below is to an article that takes a look at efforts to save Australia’s wildlife.

For more visit:
http://theconversation.com/from-the-frontline-saving-australias-threatened-mammals-28337

AUSTRALIA: ENVIRONMENTAL CRISIS – Massive Extinction Threat


Australia is facing an environmental crisis with a possible massive extinction threat due largely to human activities. The latest Red List by the International Union for the Conservation of Nature lists 788 plant and animal species as threatened in Australia, including 57 mammals, 44 birds, 38 reptiles and 48 amphibians.

The Tasmanian Devil is one of the most at risk Australian mammals, with a huge fall in numbers because of a deadly facial tumour disease.

The biggest threats to Australian species are introduced species including foxes, feral cats and cane toads.

The Red List has some 16 928 species on a global scale now facing extinction, with 3 246 of those species listed as critically endangered.

BELOW: A report dealing with the Red List