Feral goats are an invasive animal species in Australia. First arriving in the 18th century with European settlers, feral goat populations originated from escaped domestic individuals. Today, feral goats are found across Australia, where they cause economic and environmental damage through overgrazing and competition with livestock and native marsupials.
History
Feral goats came to Australia with the first fleet in 1788. For instance, cashmere goats were brought into South Australia in 1837. In the 1860s, angora and cashmere goats were imported from Asia in an order to start a goat fibre industry. Some herds were set free when the industry collapsed in the 1920s. Goats were also taken around Australia with settlers, railway construction groups and miners. The recent populations of the feral goat have established from goats used to control weeds in plantation forests and woody weeds in inland New South Wales and Queensland. The current feral goat populations in Australia represent a mixture of these origins.
Distribution
Feral goats are found in all states and in the Australian Capital Territory but are rare in the Northern Territory. They are at their highest densities in the arid and semi-arid rangelands, where they are considered a significant agricultural and environmental pest. People, through supplying water and controlling predators to improve sheep production, have modified the natural habitat favourably for feral goats.
Feral goats also occur on many Australian offshore islands. These include islands with important conservation values, such as Lord Howe Island, and islands in the Archipelago of the Recherche. Island populations are generally considered to be pests but the feral goats on North Goulburn Island provide a source of trophy animals for a safari operation run by the Aboriginal owners and also provide food for the owners while they visit the island. Feral goats have been eradicated from several islands including Faure Island, Bernier Island, Woody Island and Townshend Island. The establishment of new island populations is now less likely than in the past, especially in South Australia where the Animal and Plant Control Act 1986 prohibits the keeping and release of goats on nearly all islands in that state. The chance of natural colonisation of islands is remote as goats will swim (or even wade) only under dire need, but perhaps not impossible because goats have been reported to swim to obtain fresh water.
There were about 2.6 million feral goats in Australia in 1993 but this number has fluctuated widely. The fluctuations in number depends upon the quality of available food, availability of water, natural predation, hunting by people and deaths due to diseases, parasites and poisonous plants.
Economic impact
Feral goats are responsible for an estimated loss of $25 million per year. These are derived from a calculated $17.8 million net loss due to reduced stock production, $6 million contingency loss due to the threat of exotic disease and $1.2 million spent by the government agencies on goat control operations. This estimate does not include the costs associated with the impact of feral goats on the environment, of soil erosion, or pastoral degradation.
Commercial exploitation of feral goats is an industry worth about $29 million annually. Many pastoralists in Australia now consider the capture and sale of feral goats to be an essential part of their business. Meat for export is the main product from feral goats. Some live feral goats are also exported. Goat skin is a by-product. Recently, feral goats have been crossed with the South African Boer goat to produce a heavier animal for export.
Feral goats are also used as a biological method of controlling weeds such as blackberry (Rubus fruticosus), briar (Rosa rubiginosa), serrated tussock (Nassella trichotoma), St John's wort (Hypericum perforatum) and thistles (family Asteraceae). They are particularly useful for controlling heavy weed infestations in difficult terrain. Goats have a preference for such weeds over other pasture species. Control of these weeds is usually expensive and herbicides are not appropriate in some environments.