Fourteen feral cats captured in the wild have been re-released to measure their predation on native animals.
The cats wear collars that track their whereabouts and activities through video, GPS and VHF beacons as part of the NESP TSR Hub’s Integrated management of feral herbivores and feral predators (Project 1.1).
The research, led by Dr Hugh McGregor from the University of Tasmania, seeks to understand how the hunting behaviour of feral cats changes post-calicivirus (when rabbit numbers suddenly fall), including by measuring the occurrence and impacts of pre-switching by cats.
There are long-term gains to native plants and animals resulting from the reduction in rabbit numbers through use of calicivirus (through improvements to vegetation as well as overall reductions in the densities of foxes and cats) but there may also be at least short-term detriment to some native animals.
“After calicivirus, the sudden scarcity of rabbit numbers could cause cats and foxes to ‘prey switch’ to native animals. In some circumstances, prey-switching could cause the local extirpation of a population of native species. For example, we think that the loss of some populations of rock-wallabies in the arid zone may have occurred because of prey-switching after the first calici virus release,” says Hugh.
Hugh aims to discover whether prey-switching occurs, and if so how it can be managed. He also aims to identify the threshold density of rabbits that results in cat densities with minimal impacts on native species.
“By describing the hunting behaviour, including the kill rates and prey choice of feral cats, we can make better calculations of the impacts of prey switching on native populations.
“We’ve been tracking the cats for a couple of months already, since July, and very early video footage is showing that the cats are hunting selectively around rabbit warrens and preferring rabbits as prey.
“When the footage shows a cat preying on a native animal, it can be quite confronting. The native animals are clearly unused to being hunted by such a predator.”
Image: feral farm cat, by Stavrolo
New Hub research has quantified the extent of predation by cats on Australia’s birds and identified the species and types of birds most vulnerable to cats. The team found that cats kill over 1 million birds per day in Australia. The total is made up of an estimated 316 million birds killed by feral cats and 61 million killed by pet cats each year.
Sound recorders have been installed across farm land in south-western Victoria and on Kangaroo Island in research to help threatened glossy black-cockatoos and south-eastern red-tailed black-cockatoos, by learning more about their breeding.
As cats and foxes have spread across Australia, islands have prevented the extinctions of several mammals like the boodie. Associate Professor Sarah Legge discusses the importance of safe havens and also summarizes the highlights of a recent 'safe-haven' symposium held at the International Mammalogy Congress in Perth.
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On sub-Antarctic Macquarie Island a multi-million dollar eradication program removed cats in 2000 and rabbits, rats and mice in 2013. In the aftermath of this effort, beautiful things are emerging. Dr Justine Shaw is leading a TSR Hub project to learn from this experience and monitor how ecosystems respond.