Generally speaking, feral cats are those domestic cats Felis catus which survive and reproduce without a close association with man. However, their status is very variable and feral cats may live either in close proximity to human habitation or be completely isolated in the bush.
The two extremes are represented by urban populations of stray cats which obtain much of their food by scavenging human food scraps and supplement their numbers by the recruitment of strays, and remote populations which survive by hunting naturally occurring prey and maintain their numbers solely through reproduction.
The situation is further complicated by the existence of semi domesticated farm cats and roaming domestic cats, so no completely precise and all embracing definition of feral cat is possible.
Feral cats should not be confused with two of our larger native marsupial predators, Eastern Quolls and Tiger Quolls (previously called “native cats” and “tiger cats”). Domestic cats were first brought to Australia by Europeans.
Feral populations may have begun to establish soon after initial European settlement. The major spread of feral cats throughout inland Australia took place last century as the continent was opened up. Today feral cats exist over much of
Australia and have successfully colonized most habitats. In Victoria, feral cats are distributed throughout the State, from the high rainfall areas of the eastern highlands to the semi-arid Mallee.
Biology:
Feral cats are similar in size and physical appearance to typical suburban domestic cats. Feral cats adult males normally weigh from 3.4 to 6.4 kg (average weight 4.5 kg) and adult females from 2.4 to 4.4 kg (average weight 3.2 kg).
The most common coat colour of feral cats is striped tabby but blotched tabby and black are also common. Other colours to occur are striped and blotched orange and sometimes tortoise shell. Long hair is uncommon in feral cats and exotic or fancy breeds of cat such as persian or siamese are not found in feral populations.
Feral cats are opportunistic predators and will eat a wide variety of foods. Their diet at any time will usually consist of those species of prey most available to them. Dietary studies have shown that the European wild rabbit is the major food item of feral cats in Victoria, but mice, smaller native mammals, reptiles, birds and invertebrates are also eaten.
However, when live prey is scarce, feral cats will also scavenge food scraps. Reproduction in feral cats is similar to that in domestic cats. On average, females have two litters per year, the first in spring and the second in late summer or early autumn.
However, litters may be dropped in any month and litter size usually ranges from two to seven with a mean litter size of 4.4. Under favourable conditions, the offspring remain with the mother until approximately seven months old but then this family group gradually splits up and the individuals change to a solitary existence.
As adults, feral cats usually maintain discrete home ranges which may be up to 10 sq km in area for males and somewhat less for females. Home range sizes may depend upon available food supplies but when local foods become scarce they will undertake longer migrations.
Population densities vary seasonally with reproduction and also in relation to the food supply. When prey is abundant, cat population densities increase and, when prey is scarce, their densities decrease. Thus, no accurate density figures can be given but at one study site in the Mallee, the mean winter density was 0.7 cats per sq km.
Although feral cats may be active at any time, they are usually more active at night, with the two periods of greatest activity centred near the times of sunrise and sunset. Often during the day, feral cats will lay up in sheltered areas, usually in rabbit burrows, hollow logs or dense thickets of scrub.
Feral cats collected in past surveys were found to be healthy and well fed. However, the normal range of parasites found in domestic cats such as tapeworms and roundworms, and diseases such as feline panleukopaenia and toxoplasmosis also exist in the feral populations.
Disease transmission and environmental damage:
The disease toxoplasmosis can be transmitted by cats to humans, domestic stock and some native animals. The disease can cause foetal disease and miscarriage but the role that feral cats play in the transmission of this disease is thought to be slight.
Apart from their potential as carriers of disease which may be harmful to stock or native animals, feral cats do not cause any significant economic damage. Observations in wildlife habitats throughout Victoria indicates feral cats prey heavily on small indigenous mammals and birds.
It is possible that feral cats may exert a detrimental effect on small carnivores such as the tiger quoll, eastern quoll and the brush tailed phascogale by direct competition for food. They may also have played a significant role in some extinctions, particularly when introduced to islands, eg. causing the local extinction of the ground nesting parakeet on Macquarie Island, but hard evidence on their ecological impact is difficult to obtain.
Because feral cats are widespread throughout Victoria, no large-scale control methods can be applied to them, and in some areas they may have reached a state of equilibrium within their habitats.
However, in areas of special concern such as National Parks or areas where endangered species of birds or small mammals exist, traditional control measures such as shooting and trapping can be used.
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