Cats in Australia

1860s

With a growing agricultural industry, in the 1860s cats were deliberately introduced into agricultural areas outside of the main settlements. In 1864 a mass release of cats in the Lachlan River in New South Wales was aimed at controlling a rat plague.^[14] Similar introductions to control rodent plagues occurred in rural areas of Western Australia and Victoria in the 1860s, and the Warrego River in Queensland in 1874.^[14] Cats were seen as particularly effective at controlling occurrences of the bush rat or dusky field rat in farming land.^[14]

By the mid-1860s, cats were themselves at times considered a pest. At Barwon Park, Victoria in 1868, one of the first recorded cullings occurred, with over 100 feral cats found to be nesting in rabbit burrows.^[14]

Promoted under government policy as a rabbit control, cats were first released in the 1880s in Victoria's Wimmera, as well as in outback South Australia.^[14] While their ability to catch rabbits was often praised, rabbit trapping was considered a far more effective method and the releases simply aided the cat's spread across outback Australia.^[14] Observers in far outback Queensland and New South Wales noted that cat populations had begun to grow in number during the 1880s.^[14] The first recorded "plague" of wild cats occurred in Thargomindah in 1888 after which local farmers began to place a bounty on them.^[14]

By 1890 cats had spread to their approximate current mainland distribution of over 90%.^[15] Feral populations were growing in remote Western Australia and Victoria in the late 1890s.^[14] Despite this, they continued to be released throughout remote areas of Australia in an effort to control rabbits.^[14] For many decades the problem of feral cats was often overlooked as for many it was sight unseen, with cats most actively hunting at night.

20th century onward

In the early 1900s concern was expressed at the pervasiveness of the cat problem.^[16]

The 1920s saw a change of opinion and some began to regard the introduction of cats for pest control as a failure and proclaimed them a pest. The Naturalist, writing for the Australian, was of this sentiment.^[17] Professor Wood Jones attributed the threat of bird and marsupial life in the outback to the practice of dumping kittens in rabbit warrens in outback cattle runs.^[18] British naturalist Dr Leach in 1923 wrote of a startling decline in Australian birdlife, particularly parrots and concluded that feral cats have "got to be reckoned with".^[19] Feral cats were also, by this time, present on most islands.^[20] The Royal Society of South Australia met to discuss the issue in 1927.^[21] A war was declared on cats in 1929 were common in rabbit burrows, grew far larger than domestic cats, and began to be hunted for their skins.^[22]

During the 1950s, Myxomatosis was introduced in an effort to control rabbits. This had the effect of cats searching for other sources of food.^[23]

During the 1950s and 1960s the Sydney Harbour Bridge south eastern pylon was home to a family of world-famous white cats.^[24]

In the 1970s the belief that pet owners were responsible for the feral cat problem became common. This was partly due to an increase in the prevalence of feral cats in urban areas, many believed to be strays.^[25] It was also because the RSPCA placed the blame on those disposing of unwanted kittens in the bush and called for pet ownership restrictions.^[26] Popular opinion was that most feral cats originated as unwanted or uncontrolled house cats.^[27][28][29] Cats became a particularly bad problem for on King Island to pheasant populations where groups were lobbying authorities to introduce bounties.^{[30][31][32][33]} Cats up to a metre long were shot in Western Australia.^[34]

Prior to the late 1970s opinions as to whether the red fox or cat was the bigger pest tended toward the fox. However, in the late 1970s and early 1980s local extinctions of marsupials began to be attributed directly to feral cats.^[35] Cats were the bigger pest, according to experts in the early 1980s, especially to endangered birdlife.^[36][37][38] Cat eradication programs began to be called for on some islands such as Reevesby Island.^[39][40]

A feral cat eradication organization was formed in 1991.^[41]

Ecological impacts

Despite the indications of being pests, cats were intentionally released to the Australian wilderness in 1860s as a measure to tackle introduced rats and rabbits, and may have been effective especially on remote islands.^[14][48][49] However, as they went feral and multiplied, they have been viewed as a major invasive species and an ecological disaster in the continent. Cats inhabit among variety of environments, and have been linked to the decline and extinctions of various native species most notably ground-nesting birds and small mammals.^[50][51][52]

Feral cats, along with foxes are ranked as the highest threat to Australia's mammals and are among the top priority to tackle by the Australian Government. Damages by cats include stresses on over 200 nationally threatened native fauna and flora, such as annual kills of over 1.5 billion native vertebrates and 1.1 billion invertebrates, and potentially the extinctions of at least 28 mammal species and the paradise parrot.^[53][54][55] Each cat may kill 740 wild animals per year,^[56] and they have also hampered attempts to reintroduce locally extinct species.^[57]

Economic impacts

Cats are the costliest invasive species in Australia.^[70] The cost of invasive cats to the national economy is estimated to be nearly A$19 billion over the 60 years up to 2021, with most of the cost spent on population control. This cost significantly outstrips the next most costly invasive species, with rabbits in Australia coming in at nearly A$2 billion.^[71]

Control

Cats are difficult to control for their behavioral patterns, agility, and reproduction rates to overcome artificial barriers, trapping, and baiting.^[72][73][74]

Dog detection is effective to find cats.^[75] For trapping, Trap–neuter–return is the most favored method by animal welfare groups, although the logistics are difficult particularly in remote regions, and it may stabilizes cat populations instead.^[76][77]

Shooting is the most commonly taken measure. Ground shooting is effective and resource intensive, while cats often evade and survive aerial shooting. However, shooting is generally expensive and ineffectual to address the source of the problem, and has been a topic of animal welfare issues.^[72][78] Some varmint hunters, such as Barry Green, face backlash and even death threats for the culling of the feral cats.^[79][80][81]

Baiting is preferred to avoid harms on native species, but is also expensive and its effectiveness has been questioned. Baiting in some jurisdictions, such as Victoria and Queensland, is subject to restrictions, and animal welfare groups advocate for alternatives.^[82][83]

Exclosure fences may ease the control particularly on islands, however it requires complex constructions and can be extremely expensive.^[84] Following the 2019–2020 bushfires, an exclusion fence had been built on private property around some of the burnt land in Kangaroo Island.^[85]

The idea of reintroducing Tasmanian devils has been proposed, due to their effectiveness in cat control in areas where they are present, however has not gained traction.^[63]

Eradication

In 2016, the federal government announced a program to eradicate cats from Bruny Island, French Island, Christmas Island, Dirk Hartog Island and Kangaroo Island.^[86]

Kangaroo Island's population is estimated at between 3,000–5,000 and is targeted at being cat free by 2030.^[87][88] The 2019–2020 bushfires complicated eradication efforts, as the gradual regrowth of the burnt brush creates cat habitats and increased difficulty to hunt.^[89] By the end of 2021, at least 850 cats had been removed from the burnt area at the western end of the island using grooming traps with state-of-the-art technology and cameras.^[90]

Pintupi, Nyirripi, and other Western Desert peoples in Western Australia and Northern Territory have been hunting cats for food sources and bush medicine for decades. In 2015, they also participated in a controlling program.^[91]