Publications archive - Biodiversity
Key departmental publications, e.g. annual reports, budget papers and program guidelines are available in our online archive.
Much of the material listed on these archived web pages has been superseded, or served a particular purpose at a particular time. It may contain references to activities or policies that have no current application. Many archived documents may link to web pages that have moved or no longer exist, or may refer to other documents that are no longer available.
Biodiversity Group Environment Australia, 1999
ISBN 0 642 54634 7
The feral goat in Australia has been derived from a variety of domestic goat breeds that were introduced to provide meat, milk and fibre. Feral goats are defined as those animals which have escaped the ownership, management and control of people and are living and reproducing in the wild (Parkes et. al. 1996). Feral populations were established when domestic herds were deliberately released or animals escaped (McKnight, 1976). These populations survived and proliferated in many environments for reasons such as high levels of fecundity, lack of predators, freedom from disease, high mobility, and diverse diet (Henzell, 1992a). It is important to recognise that the key difference between a feral goat and a domestic goat is that the latter is secured behind a fence while the former is not subject to any form of intensive control nor permanently restrained by any fences.
Feral goats are found in most regions of Australia, with the highest densities seen in the arid and semi-arid pastoral regions of Queensland, New South Wales, South Australia and Western Australia (Parkes et. al. 1996). Southwell et. al. (1993) estimated that nearly one million feral goats exist in eastern Australia. This figure is probably an under-estimate since it was based on uncorrected aerial counts. Parkes et. al. (1996) estimated approximately 2.6 million feral goats in Australia. However, they consider this a conservative figure in view of the number of goats harvested each year.
Feral goat populations are capable of increasing by up to 50 per cent each year under favourable environmental conditions (Mahood, 1985; Maas and Choquenot, 1995; Parkes et. al. 1996). They are a generalist herbivore (Coblentz, 1977) and can occupy a great variety of habitats. In the arid and semi-arid regions of Australia they tend to be primarily browsers switching to grass and forbs when these are green (Wilson et. al. 1975; Harrington, 1986). Their feeding habits in more temperate regions tend to be seasonal (O'Brien, 1984). Feral goats need to water every two to three days during summer (Dawson et. al. 1975), but can otherwise extract most of their water requirements from their food.
The distribution of the feral goat does not totally reflect its generalist dietary habits. Its presence in various environments is thought to be limited by several factors, including the type and nutritional quality of vegetation; the availability of shelter; the need to drink water during dry times; the occurrence of various parasites and diseases possibly resulting in the goat's absence from wetter parts of the country (Harrington, 1982); and predation from dingoes and feral dogs, which is believed to limit their populations in areas where these predators occur (Parkes et. al. 1996).
The feral goat is a very successful invader of a variety of habitats including the arid and semi-arid rangelands and an assortment of offshore islands (Parkes et. al. 1996). At least 20 goat-sized herbivores per square kilometre can be supported in rangelands with annual rainfall of 240 millimetres. Estimates of goat densities range from two (average density in all States during the early 1990s) to five (estimate in more preferred habitats) per square kilometre. At these densities feral goats would be contributing from ten per cent to twenty-five per cent of the total sustainable grazing pressure (Parkes et. al. 1996). Management of feral goats will need to be integrated with the management of other large herbivores to ensure that the total impact of grazing on the vegetation is maintained within ecologically sustainable limits.
The feral goat is reported as responsible for a variety of impacts on native flora and fauna. These include competing with native fauna for food, water and shelter (Lim et al, 1992) and threatening the survival of native flora through their feeding habits (Auld, 1993). Destruction of vegetation is also thought to cause soil erosion (Yocom, 1967). It is for these reasons that it is listed as a Key Threatening Process under Schedule 3 of the Act.
Feral goats have been identified as a confirmed threat or a perceived threat to several endangered and vulnerable species listed under Schedule 1 of the Act (Table 1).
|Leipoa ocellata||Malleefowl||(Benshemesh, J., 1998)|
|Acacia araneosa||(Davies, R.J-P., 1990)|
|Acacia barattensis||(Davies, R.J-P., 1995)|
|Cynanchum elegans||(Matthes, M. & Nash, S., 1993)|
|Drakonorchis drakeoides||(Holland, E., et. al., 1997)|
|Eriocaulon carsonii||(Pickard, J., 1992)|
|Grevillea beadleana||(Gross, C.L. & Steed, A., 1997)|
|Grevillea iaspicula||(Butler, G., et. al., 1991)|
|Westringia crassifolia||(Davies, R. & Riley, M., 1993)|
|Petrogale lateralis||Black-footed Rock-wallaby||(Hall, G.P. and Kinnear, 1991)|
|Petrogale penicillata||Brush-tailed Rock-wallaby||Hill, F.A.R., 1991)|
|Petrogale xanthopus||Yellow-footed Rock-Wallaby||(Dawson, T.J. and Ellis, B.A., 1979;
Sheppard, N. 1990)
|Pseudomys fieldi||Djoongari||(Morris, K. , et al,.1997)|
|Brachyscome muelleri||(Jusaitis, M., 1998)|
While key threatening processes are listed because of their impacts on listed threatened species, impacts from feral goats are not restricted to these species. Feral goats are also known to be seriously affecting the demographic status of several currently widespread tree species in the rangelands (Henzell in litt.). Such species include Alectryon oleifolius, various Santalum species
(including S. acuminatum and S. spicatum) and Capparis mitchelli. While mature specimens of these trees are unlikely to be threatened by mammalian herbivores, grazing is a significant threat to survival and recruitment of juvenile plants. Best practice management of feral goats must involve action to reduce the threat not only to targeted threatened species, but to all potentially vulnerable native species.
For each process listed in Schedule 3 of the Act, a nationally coordinated threat abatement plan must be prepared and implemented. The Act prescribes the content of a threat abatement plan and the mechanisms by which plans are to be prepared, approved and published. Where a threatening process occurs in more than one jurisdiction, the Commonwealth must seek the cooperation of the relevant States and Territories in the joint preparation and implementation of a threat abatement plan.
The feral goat has not been eradicated from any extensive mainland environment in Australia, despite decades of control effort. Eradication from island habitats, however, has been successfully achieved in Australia (Daly and Goriup, 1987; Allen and Lee, 1995) and New Zealand (Parkes, 1990), and should be considered an option to protect native species and ecological communities on Australian islands where goats still exist.
The most common management techniques currently used to control feral goats are mustering, trapping and aerial shooting. Mustering and trapping have the advantage of providing the option of humane slaughter or sale of captured animals. Aerial shooting is used in inaccessible terrain. It is advocated as being the most effective technique currently available for such areas and is considered humane when conducted by trained shooters using suitable weapons. Other techniques that are occasionally used or are the subject of research are ground-based shooting; using Judas goats; poisoning; and predation by dingoes. Non-lethal techniques such as fencing and habitat manipulation have also been investigated.
The success of this threat abatement plan will depend on a high level of cooperation between all key stakeholders, including landowners and managers, community groups, local government, State and Territory conservation and pest management agencies, and the Commonwealth Government and its agencies. Success will only be achieved if all participants are prepared to allocate adequate resources to achieving effective on-ground control of feral goats at critical sites and in critical regions, improving the effectiveness of control programs and measuring and assessing outcomes.
This threat abatement plan will need to be complemented by appropriate plans for managing domestic goats. Commercial harvesting of feral goats is acceptable practice providing that is done in accordance with the national code for the destruction, capture, handling and marketing of feral animals. However, there is the danger that some landholders may seek to 'farm' feral goats, thereby maintaining high densities.
By taking a measured, stepwise approach, recognising the realistic limitations and opportunities that exist, and ensuring that field experience and research are applied to further improve feral goat management, the threat abatement plan will ensure a responsible use of public resources and give the best outcome for wildlife.