– January 20, 2020 – Science
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- Should cats be shot to save Australia’s ecosystem after the fires?
In Australia, recent thunderstorms and heavy rainfall are gradually putting out fires. If this signals the gradual end of an historic ecological disaster caused by climate change, the impact will be profound and its effects will be long-lasting. With more than a billion dead animals, Australia’s biodiversity is at risk, more than ever before. In this context, and as raised by Wired, cats are among the threats that increase this vulnerability. This sad observation is justified by several recent studies.
The problem is mainly caused by stray cats, i.e. domestic cats that have returned to the wild. Long before the severe fires of 2019-2020, their overabundance was already considered a threat to the regional ecosystem. They inhabit 99.8% of Australia’s land area; their population varies between 2 and 6 million and their density can be as high as 100 individuals per square kilometre. In 2015, the government announced in a report the choice to cull two million stray cats. That is why, in 2019, a poisoned sausage, intended to target them, was spread over the territory.
An Australian stray cat with a bird as prey // Source: Central Australian Museum, Alice Springs / Mark Marathon
The reason Australia is coming to such extremes is because these animals are devastating the ecosystem. According to a study published in Biological Conservation in 2017, cats kill 377 million birds and 649 million reptiles each year. Other results, published in 2019 in Nature, evoke 800 million mammals killed each year by stray cats. They are responsible for several mammalian extinctions, many species are endangered because of them, and they actively contribute to the vulnerability of many others.
The cause is not only their presence in numbers as well as their predation, but that stray cats are not native to Australia: they were introduced by European settlers. On the scale of the evolution of life on Earth, that’s a short time. Species endemic to the Australian Territory – those that originated there – have not had time to adapt to these predators. Cats are not a “natural” threat from an ecosystem perspective, since they had no business being there in the first place.
- Read: Climate change: Australian fires will degrade the ecosystem forever
Fire starts have always been common in Australia, so much so that the region is favourable to them. But climate change is causing global warming that particularly affects the Australian continent. This area of the world is getting hotter and hotter, drier and drier, so the thermometer has recently been able to approach 49 degrees. So climate change is only increasing fires in Australia.
Cats are better predators in areas recently affected by fires.
During the episode from September 2019 to January 2020, more than 10 million hectares were burned. This implies a large-scale loss of forest cover. The trees are slowly growing back. This is where a link is forged with stray cats: a 2015 study revealed, through video experimentation, that stray cats are “better predators” in open environments… which is precisely the case when forest cover disappears. In such an environmental context, 70% of their attacks on their prey are successful.
For hunting, stray cats are even particularly attracted to areas that have recently suffered a fire. They prove to be better hunters there, especially when it comes to wounded or weakened animals. Except that they finish them without necessarily consuming them afterwards. “The intensification of fires will have serious consequences on the decline of prey species,” concluded a research paper in Wildlife Research.
- Read: Are we experiencing the beginnings of the sixth mass extinction?
After a fire such as the historic episode that Australia has just experienced, cats will therefore pose a heavy threat to species already weakened by the event itself. The situation is all the more tragic because this threat of one species on others was originally introduced by humans themselves.