Cats and foxes are invasive and preliferious predators in Australia, devastating populations of small animals and hunting others to extinction. A new study published in Diversity and Distributions shows just many animals they kill each year.
Researchers found that cats and foxes wipe out 697 million reptiles, 510 million birds and 1.4 billion small animals annually in Australia. In total, about 2.6 billion introduced and native small animals are killed by just these two predators. Foxes alone kill about 300 million native animals.
“This enormous death toll is one of the key reasons Australia's biodiversity is suffering major declines,” the authors write in an article in The Conversation. “Cats and foxes, for example, have played a big role in most of Australia's 34 mammal extinctions, including the desert rat-kangaroo which rapidly declined once foxes reached their region.”
The researchers also mapped how many and where these animals live in Australia, finding approximately 1.7 million foxes live on the continent and cover about 80 percent of the mainland. About 6.6 million feral and pet cats live in Australia and cover about 99.9 percent, per the study.
Foxes tend to eat larger prey and have a bigger impact on kangaroos, wallabies and potoroos. Cats, on the other hand, eat larger quantities of smaller animals, killing about five times more reptiles, two and a half times more birds and twice as many mammals as foxes, per The Conversation.
"They've got different size preferences that overlap and the poor buggers in the middle are getting a double whammy," study co-author Sarah Legge, a wildlife ecologist at the Australian National University, tells Nick Kilvert from the Australian Broadcasting Corporation (ABC).
Foxes were released into the wild in Victoria starting in 1845 for sport hunting, per The Conversation. Their population skyrocketed after the introduction of rabbits and hares in the 1800s, and these animals continue to boost fox numbers today. Colonizers also brought cats to the continent.
While there’s no “silver bullet” solution for cat and fox population control, keeping pet cats away from wildlife is one approach, ecologist John Read from the University of Adelaide, who wasn't involved in this study, tells ABC.
"Management of domestic cats is a huge issue," he tells the publication. "Keeping cats contained helps prevent those environmental and health impacts and stops them getting out and breeding more feral cats.
According to the authors, this is the first study to quantify the impact of foxes on wildlife in Australia.
“We already had good information about the cats’ impact on other species. This research gave us a clearer picture on the impact of both species nationally and in different and more remote environments,” lead author Alyson Stobo-Wilson, a community ecologist at Charles Darwin University, says in a statement.
The authors conclude that the country needs better management of cats and foxes as well as better protection and habitat recovery for native animals.
“Australia must drastically scale up the management of both predators, to give native wildlife a fighting chance and to help prevent future extinctions,” they write in The Conversation.