Flaviemys purvisi
Very Well-Known Member
By Joe Hinchliffe
23 June 2018
Semi-digested bodies are strewn across the table. Amid the blood and bile lie a knife and the killer – a feral cat.
The blade has been used to spill the contents of the cat’s stomach. The dozens of small mammals, lizards and snakes have all been eaten within the past 24 hours.
That is roughly how long it takes a cat to digest its food, which it mainly eats whole. Both factors make doing the sums on feral cat predation fairly straightforward – provided you know how many cats are out there, and you can access enough of their stomachs.
That is exactly what researchers at the NESP Threatened Species Recovery Hub have done.
"Killing cats then pulling apart their digestive tracts ... it's not the funnest job in the world by any means," lead author John Woinarski said.
"But it's a very valid means to get a good idea of their diet."
Dr Woinarski's team has compiled the results of more than 10,000 dissections and examinations of cat scat, as well as new estimates of their population, to crunch the numbers of native animals falling prey to feral cats.
Last year they revealed that cats eat more than a million birds every day in Australia. But that figure has been eclipsed by the number of reptiles killed by feral cats.
The second part of the team's research, released this week, shows 1.8 million reptiles fall victim to the feline predators every day.
In years or abundance, feral cats alone could eat more than 3.5 billion reptiles in the wild.
And that figure tells only part of the story – it excludes reptiles eaten by house cats and stray cats, and those in modified environments such as dumps and piggeries, where felines abound.
The number of mammals killed by cats will be revealed in coming months in the final part of the study.
But while the devastation wreaked by cats on native marsupials and birds is well recognised, Dr Woinarski said few people were aware of the plight of our reptiles – including some of the most "distinctive and unusual on Earth".
About one in 10 of the world's reptiles call Australia home and more than 90 per cent of those are found nowhere else in the world.
"The reptile species we're most worried about cat predation for are the relatively large, slow-moving, long-lived species that live on the ground," Dr John Woinarski said.
"Things like blue tongues, shinglebacks, frilled-neck lizards, thorny devils ... a whole group of those are probably declining, largely due to cat predation.
"When I was a boy I lived in the suburbs of Melbourne and we had blue-tongued lizards quite happily running around our garden – that's no longer the case that most people have that privilege."
The study found more than 250 Australian reptile species were known to be killed by feral cats, including 10 species listed as threatened.
The greatest number of feral cats – whose population fluctuates between 2 million and 6 million –were found in arid regions, where lizards abound.
These distribution patterns put such species as the great desert skink in the firing line. But it isn't just lizards: threatened pygmy copperheads are among many species of snake in decline because of feral cats.
Another surprising find in the study was feral cats' tendency to "binge" on favoured species – one cat stomach yielded 40 lizards of the same species it ate that day.
Such focused hunting means local populations could be quickly wiped out.
While comparatively little is known about how Australian reptiles are faring against the onslaught of cat predation, the picture is set to become clearer this year when the International Union for Conservation of Nature releases the conservation status for every Australian reptile for the first time.
