In last week's Summit Sun we exposed the explosion in feral cat numbers in Jindabyne's town centre. We reported on the concern being expressed by business owners who wished to raise awareness in the local community and to bring the issue before council. In this issue, we asked an expert for her analysis of the situation - Dr Linda Broome, Senior Threatened Species Officer,Office of Environment and Heritage provided the answers.
Q. Would feral cats in Jindabyne come from the national park?
A. It is unlikely that the feral cats are coming from the National Park. There are feral cats throughout the National Park and on private properties and State Forest around the Park but the highest numbers are concentrated around areas of human activity, eg around the ski resorts at Perisher Valley -Blue Cow -Guthega and around Thredbo, as well as around townships such as Jindabyne. Rubbish tips and garbage bins are favourite haunts where the cats can find food scraps as well as feral rats and mice. They do of course also eat a lot of native wildlife including our endangered Mountain Pygmy-possums and Broad-toothed Rats around the ski resorts and even on Mt Kosciuszko and Muellers Peak.
Q. Why would they be moving into the township?
A. They are probably increasing in numbers due to good breeding conditions rather than moving into the township from surrounding areas (although we can't prove this definitively unless we tagged or radio collared the cats!).
Jindabyne is 8-10 km from the Park and conditions have been good for the last three years inside as well as outside the Park due to good rainfall so small mammal, reptile and bird numbers have probably increased throughout the area (small mammals certainly have) and there is no reason why the cats would need to move out of the Park to find food elsewhere. Female cats can begin breeding at seven months of age (usually between 7-12 months) and have three litters of up to eight young in a litter during a year. If you started with one cat having for example six kittens three times a year and half of her kittens were females breeding at seven months of age you could have 349 cats in two years and four months time.
Q. Do they pose any danger to residents particularly children?
A. Feral cats do pose a serious health risk to humans, livestock and native animals as carriers of diseases such as toxoplasmosis and sarcosporidiosis. These are infections of protozoan parasites that use the cat as a host and pass from cats to other animals via oocysts in cat faeces. Children playing in sandpits that have been used by cats to defecate are particularly susceptible.
Toxoplasmosis can cause abortions and still births in humans and animals and is also a great concern in babies before they develop their immune systems. In adults (human and animal) toxoplasmosis can result in cysts in the muscle tissue and can affect heart, liver, eyes, brain and neurone function. Not a great deal is known about the disease but studies have shown that the parasite is able to subtly affect the behaviour of its host: one study showed that infected rats and mice were less fearful of cats, in fact some of the infected rats sought out areas marked with cat urine (you can imagine how this would be an advantage for the parasite).
Up to a third of the human population is estimated to carry a toxoplama infection but unless they have weakened immune systems people usually do not show symptoms following the initial infection. However, recent studies suggest that acute toxoplasmosis in humans may be more disabling than previously thought and may be associated with chronic fatigue, headaches, difficulty in concentrating, fever, ADHD, depression and schizophrenia.At this point I don't know what proportion of the feral cats we have been catching are infected with toxoplasmosis but we have started collecting blood samples to test for this.
Q. How do you tackle them in the national park?
A. Cats are notoriously difficult to control because unlike foxes, they are reluctant to take baits. They can also be very wary of human scent, although the ones that hang out around areas of human habitation such as the ski resorts, town centre and rubbish dumps are probably easier to trap than back country cats. We have had a trapping program for feral cats around the Perisher, Charlotte Pass and Thredbo resorts since 2002.
Initially we used cage traps baited with tinned cat food during the winter, when cats are likely to be hungry and less able to find live food. In 2002 we removed 30 cats from the Perisher-BlueCow-Guthega area and 20 cats in 2003, then about six per year until 2010 (90 cats total up to 2010). By putting out infra-red detection cameras we concluded there was a proportion of the cat population that was too wary to go near a cage trap so we now use detection methods then place soft-jawed leg-hold traps strategically, removing another 19 cats during the first summer (2011).
Q. What should be done in Jindabyne to counter them?
A. I would recommend that the problem be taken to the local council who may consider initiating a cat trapping program. If residents have concerns about pet cats they should have them microchipped so they can be identified. All pet cats should be desexed, micro-chipped and kept indoors if possible - certainly at night (note that pet cats can also carry toxoplasmosis).