Anyone with a bird feeder has experienced that sinking feeling of discovering a patch of stray feathers or a tuft of bunny fur. There's a good chance a cat has been hunting there.
Domestic cats kill small wildlife in many parts of the world, but their impact seems especially severe in Australia. Several million feral cats live there, and research suggests their daily death toll may be as high as seven animals per cat. For the sake of native species, scientists have ramped up their focus on the felines in recent years.
According to one study from 2017, feral and pet cats collectively kill more than 1 million birds in Australia every day. Its authors reached that estimate by examining 91 previous studies on cat population densities in Australia, as well as another 93 studies on what those cats hunt. Feral cats kill about 316 million Australian birds per year, the study found, while pet cats kill an additional 61 million annually.
"Everyone knows that cats kill birds, but this study shows that, at a national level, the amount of predation is staggering," lead researcher John Woinarski, from Charles Darwin University, tells the AFP news agency. "It is likely to be driving the ongoing decline of many species."
The study suggests birds are in greatest danger on Australia's islands and in remote dry areas, where cats may kill as many as 330 birds per square kilometer every year.
Birds aren't the only animals to fall victim to feral cats' fatal prowess in Australia.
A new study shows feral cats also kill about 466 million reptiles a year, higher than any other continent. An individual cat can kill up to 225 reptiles per year. The cats are essentially killing and eating 258 different reptile species such as geckos and bearded dragons, including 11 threatened species.
"Some cats eat staggering numbers of reptiles. We found many examples of single cats bingeing on lizards, with a record of 40 individual lizards in a single cat stomach," lead researcher John Woinarski told Phys.org.
Researchers note that it's hard to determine the impact on the reptiles' conservation because the population of most reptile species is unknown.
Focusing on feral cats
In another recent study, researchers from the Australian Wildlife Conservancy (AWC) outfitted more than 65 feral cats with modified GoPro cameras and GPS collars to track their daily movements. There may be anywhere from 2 million to 6 million feral cats in Australia, and the researchers hoped to clarify their ecological effects.
In what has been called a "war on cats," Australia's federal government has a five-year threatened species strategy that includes plans to eliminate 2 million feral cats by 2020. Domestic cats were introduced to the continent more than 200 years ago as pets, but many have gone wild and are dining on threatened native species.
In May 2018, the AWC completed a 27-mile electric fence around 23,200 acres in the desert as a "cat-free zone" to protect 11 critically endangered marsupials, birds and other threatened species.
The AWC's goal is to reduce the impact of those cats on native wildlife in Australia, but the research has relevance for any community with feral cats. “The purpose of the study was to examine the hunting behaviours and distances travelled by feral cats and their impact on small mammals,” said the AWC's John Kanowski.
The footage showed where the cats went and how they hunted. It showed them killing snakes, frogs and birds. Researchers found that each cat hunted 20 times a day with a 30 percent success rate, averaging seven kills per day per cat.
The cats were most successful in open areas, particularly where there had been fires that cleared the area. In those places, 80 percent of hunts were successful. But in uncleared areas, cats were only successful hunting about 20 percent of the time.
An earlier study by researchers at the University of Georgia and National Geographic found that a third of pet cats kill wildlife for an average of about 2.1 times every week. That's a lot, but nowhere near what AWC researchers have uncovered with feral cats in their 2016 study.
"This footage shows domestic cat owners that there is a big difference between domestic and feral cats," AWC chief executive Atticus Fleming told HuffPost Australia.
Fleming admitted it was not only physically challenging to strap the collars and cameras onto feral cats, but there was something of a moral dilemma, too.
"The temptation is to simply remove every cat that you catch, but when there are 4 million cats out there, removing that one cat is not actually going to help native animals," he said. "We need to use this research to find a way to remove feral cats from the landscape, or if not that, at least find a way to control them."
Editor's note: This article has been updated since it was originally published in May 2016.