The feral cat is found in nearly all habitats across Australia. It
has caused the extinction of some species on islands and has contributed to the
disappearance of many ground-dwelling birds and mammals on the mainland. Feral
cat control is feasible on islands, but elsewhere, management is difficult due
to the lack of effective and humane broad-scale control techniques, and the
presence of domestic cats.
History
Cats have been in
Australia since European settlement, and may have arrived as early as the 17th
century with Dutch shipwrecks. By the 1850s, feral cat colonies had become
established in the wild. Intentional releases were made in the late 1800s,
particularly around farms and homesteads, in the hope that cats would control
rabbits, rats and mice.
Feral cats are now found in all habitats except
the wettest rainforests on the mainland and some offshore islands.
For management purposes, cats are divided into
three categories — domestic, stray and feral — although they are all the same
species and individual cats may move between categories. Domestic cats are
owned and cared for, and stray cats are those found roaming cities, towns and
some rural holdings. Feral cats, which survive without any human contact or
assistance, are the main target of Australian Government control programs.
Ecology
Feral cats are predominantly solitary and
nocturnal, spending most of the day in the safety of a shelter such as a
burrow, log or rock pile. Rabbits have aided their spread by providing food and
burrows for shelter. There is typically one feral cat for every one to two
kilometre square but this may be larger if food supplies are scarce.
Feral cats are carnivores and can survive with
limited access to water, as they use moisture from their prey. They generally
eat small mammals, but also catch birds, reptiles, amphibians, fish and insects
- taking prey up to the size of a brush-tail possum. In pastoral regions, they
feed largely on young rabbits, but in other areas feral cats prey mainly on
native animals.
From the age of about one year, feral cats can
breed in any season. They have up to two litters of about four kittens each
year, but few of the young survive.
Dingos and
foxes may restrict feral cat numbers by both direct predation and competition. Feral cats also fall prey to
wedge-tailed eagles.
Impact
There is clear evidence
that feral cats have had a heavy impact on island fauna. On Macquarie Island,
for example, feral cats are implicated in the sharp decline of a subspecies of
the red-fronted parakeet in the 1880s and its extinction by 1891. On the mainland,
they are identified as a threat to 35 species of birds, 36 mammals, 7 reptiles
and 3 amphibians. Cats have probably contributed to the extinction of many
small to medium-sized mammals and ground-nesting birds in the arid zone, and
seriously affected bilby, mala and numbat populations. In some instances, feral
cats have directly threatened the success of recovery programs for endangered
species.
Feral cats can carry
infectious diseases such as toxoplasmosis and sarcosporidiosis, which can be
transmitted to native animals, domestic livestock and humans. If rabies were to
be accidentally introduced into Australia, there is a high risk that feral cats
would act as carriers of the disease.
Control
Conventional
control techniques of trapping and hunting have been successful in eradicating
feral cats from some offshore islands around the world, including some
Australian islands. On the mainland, management is more difficult because feral
cats are shy of traps, do not take buried baits and generally avoid human
contact, making them hard to shoot. Even if cats are removed from an area, it
is quickly recolonised.
Barrier
fencing, combined with eradication inside the fences, has proved to be
effective for protecting endangered species that are being reintroduced. For
example, fences are now used to exclude feral cats and other predators from
wildlife sanctuaries in Queensland and South Australia.
Researchers
are attempting to improve the effectiveness and humaneness of baits and traps
in controlling feral cats. In various parts of Australia, researchers are also
studying the impact of feral cats on native wildlife, so that they can target
control measures more effectively and assess how well they have worked.
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