Lamb producers have been urged not to forget the danger feral cats pose to lambing ewes after new research showed nearly 100 per cent of Australia is now covered by the feral threat.
The feral cat population fluctuates between 2.1 million and 6.3 million depending on dry and wet seasons, and the pest now covers 99.8 per cent of Australia and its islands, University of Queensland wildlife ecologist Dr Sarah Legge has found.
Not only is the feral cat a threat to Australia’s biodiversity and native wildlife - especially wallabies, grey kangaroos, bandicoots and wombats - but it threatens lamb production and human health.
The transmission of toxoplasmosis in feral cat faeces to sheep is causing grave concern in Tasmania, where wet and overcast conditions give the toxo parasite a leg up.
Tasmanian Farmers and Graziers Association ceo Peter Skillern says “abortion storms” had occurred frequently in Tasmanian lambing ewe populations. He said the other problem to producers was the threat of another parasite spread by feral cats called sarcocystis which leaves cysts in carcasses. There was a significant number of carcasses discarded at processing at abattoirs because of sarco, he said.
“There is no doubt feral cats are the biggest biodiversity threat the country faces,” ’Mr Skillern said.”Let’s also not forget toxo can be fatal to humans as well, especially to people with low immune systems, and can cause abortions in women.’’
Estimates are that Tasmania loses about $1 million a year in lost lamb production from the feral-cat bourne toxo parasite ingested by grazing sheep. It affects mainly maiden ewes, and especially twin-carrying ewes.
There is a move on to import a toxo vaccine for sheep from New Zealand, which has been able to reduce the rate of ewe abortions by three per cent, but Australian researchers have baulked at the paperwork involved to get the vaccine into Australia. The vaccine is also used in the United Kingdom where toxo is also a major problem.
Dr Legge said farmers faced an explosion in cat numbers after recent good rains across eastern Australia. She said this inevitably led to a crisis situation when drier times came and cats were competing for food sources, forcing them to move from mice and rats to native wildlife, It is estimated about 25 billion native species are eaten by feral cats in Australia every year. Dr Legge estimated the average density of feral cats in Australia was about .25 cats per square kilometre and up to .5 or .6 in bushland, with the density higher around farms.
Dr Legge said she was gratified the Federal Government had recognised what a massive problem ats posed and was backing eradication programs and research.
But she said farmers could do something at ground level to get rid of feral cats including fencing off dumps that cats use as feed centres.
“Australia’s feral cat population fluctuates between 2.1 million when times are lean, up to 6.3 million when widespread rain results in plenty of available prey,” Dr Legge said.
“Our study highlights the scale and impact of feral cats and the urgent need to develop effective control methods, and to target our efforts in areas where control will produce the biggest gains. At the moment feral cats are undermining the efforts of conservation managers and threatened species recovery teams across Australia.”
The research was funded by the Threatened Species Recovery Hub of the Australian Government’s National Environmental Science Programme.
Australia’s Threatened Species commissioner Gregory Andrews said findings substantiated the need for a humane and effective cull. “The density of feral cats in Australia is lower than it is in North America and Europe, and yet feral cats have been devastating for our wildlife,” Mr Andrews said. “Aside from Antarctica, Australia is the only continent where animals evolved without cats, which is a reason our wildlife has been so vulnerable. Feral cats have already driven at least 20 Australian mammals to extinction, which makes investing in research like this important. This science reaffirms the importance of ambitious targets to cull feral cats, which I am implementing with the support of Minister for Environment and Energy Josh Frydenberg under the Threatened Species Strategy.”