It is not known when cats were first introduced to Australia. There is some evidence they have been here for approximately 400 years, perhaps introduced by the Dutch.
Dingo chasing a feral cat.
"Intentional releases were made in the late 1800s, particularly around farms and homesteads, in the hope that cats would control rabbits, rats and mice." - The Feral Cat (Felis Catus).
It is estimated there are 400,000 feral cats in NSW, 16 million across Australia (NSW Dept Environment & Heritage, Nov 2011). Some feral cats are extremely big - almost the size of pumas. They eat small native rodents, reptiles, birds, small mammals - including bilbies and small wallabies. Cats have contributed significantly to the total extinction of a number of species and along with foxes have made Mala extinct in the wild. They also interfere with attempts to reintroduce species from captivity, such as numbats in WA.
Autopsies of shot feral cats show, on average, remnants of 6 native animals each. This means an approximation of 72 million native animals killed every night.
These feral cats were trapped May 2013 Astrebla Downs National Park in an effort to re-establish the last wild bilbies in Queensland.
In 2012, cats broke through a rusted section of a $500,000 cat-proof fence surrounding one of the last known wild colonies of Greater Bilbies, Currawinya National Park, QLD. Many cats were found inside the enclosure, although only 22 were shot. News items stated visitors to the park reported an absence of native birds, seeing only cats. No bilbies were found. Over 1000 feral cats were shot to the north, at Astrebla Downs National Park. This is in addition to another 3000 shot in the same area the year before.
The Bilby Currawinya fenced area is quite large, about 25sq km. Once the fence is repaired, the Save the Bilby Fund is hoping to repopulate the area from captive breeding programs.
Feral cats use moisture from prey. This allows them to survive long periods of time without water. They are also a pest to livestock, spreading disease and parasites, such as toxoplasmosis and sarcosporidiosis. The sarcocystis parasite is also harmful to native marsupials. Feral cats are a menace to poultry farmers with free-range chickens.
Some people promote Trap-Neuter-Vaccinate-Release (TNVR) programs as a humane and non-lethal alternative for reducing feral cat populations. Cats are trapped, desexed, vaccinated and released back into the area where they were caught. One study in America found a 30% reduction in the number of feral cats using this method, however, it is thought that at least 70% of the cat population must be treated for this to be effective. With the sheer volume of feral cats in Australia, this is obviously not practical and would also be cost prohibitive. There are no real world examples other than small isolated trials. Furthermore, because cats remain in the eco-system, it would not stop the carnage on native wildlife.
Dingoes and wedge-tailed eagles are our only natural defense against feral cats. In some areas, cats form up to 45% of a wedge-tailed eagle's diet. The presence of dingoes also changes a cat's hunting behaviour, making them less active at dusk when native animals are most at risk. Persecution and removal of dingoes and wedge-tailed eagles from eco-systems is without doubt a contributing factor to an explosion of feral cat numbers. Wedge-tailed eagles are now protected, dingoes are not. Both are IUCN listed threatened species, ironically the dingo being categorised two steps closer towards extinction. Foxes may predate smaller (very young) feral cats, adult cats are too big for foxes.
Baiting, usually with Compound 1080. Inhumane and controversial as to the efficacy of cats actually eating baits.