Feral goats are an
invasive animal species in
Australia
Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands. With an area of , Australia is the largest country by ...
. 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
Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves, or nature res ...
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
The Australian Capital Territory (commonly abbreviated as ACT), known as the Federal Capital Territory (FCT) until 1938, is a landlocked federal territory of Australia containing the national capital Canberra and some surrounding township#Aust ...
but are rare in the Northern Territory
The Northern Territory (commonly abbreviated as NT; formally the Northern Territory of Australia) is an Australian territory in the central and central northern regions of Australia. The Northern Territory shares its borders with Western Aust ...
. 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
Sheep or domestic sheep (''Ovis aries'') are domesticated, ruminant mammals typically kept as livestock. Although the term ''sheep'' can apply to other species in the genus '' Ovis'', in everyday usage it almost always refers to domesticate ...
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
Lord Howe Island (; formerly Lord Howe's Island) is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, part of the Australian state of New South Wales. It lies directly east of mainland Po ...
, and islands in the Archipelago of the Recherche
The Archipelago of the Recherche, known locally as the Bay of Isles, is a group of 105 islands, and over 1200 "obstacles to shipping", off the south coast of Western Australia. The islands stretch from east to west and to off-shore encomp ...
.[ In Parkes, John; Henzell, Robert; Pickles, Greg (1996). ''Managing Vertebrate Pests: Feral Goats''. Canberra: Australia Government Publishing Service.] Island populations are generally considered to be pests but the feral goats on North Goulburn Island
The Goulburn Islands are a group of small islands and islets in the Arafura Sea off the coast of Arnhem Land in Northern Territory of Australia. The largest islands are Weyirra (North Goulburn Island) and Warruwi (South Goulburn Island), where ...
provide a source of trophy animals for a safari
A safari (; ) is an overland journey to observe wild animals, especially in eastern or southern Africa. The so-called "Big Five" game animals of Africa – lion, leopard, rhinoceros, elephant, and Cape buffalo – particularly form an impor ...
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
Faure Island is a 58 km2 island pastoral lease and nature reserve, east of the Francois Peron National Park on the Peron Peninsula, in Shark Bay, Western Australia. It lies in line with the Monkey Mia resort to the west, and the Wooram ...
, Bernier Island
Bernier Island is one of three islands that comprise the ''Bernier and Dorre Island Nature Reserve'' in the Shark Bay World Heritage area in Western Australia.
The island and the neighbouring Dorre Island were locations for a lock hospital i ...
,[ Woody Island and Townshend Island. The establishment of new island populations is now less likely than in the past, especially in ]South Australia
South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest o ...
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 Africa
South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...
n Boer goat to produce a heavier animal for export.[
Feral goats are also used as a biological method of controlling ]weed
A weed is a plant considered undesirable in a particular situation, "a plant in the wrong place", or a plant growing where it is not wanted.Harlan, J. R., & deWet, J. M. (1965). Some thoughts about weeds. ''Economic botany'', ''19''(1), 16-24. ...
s such as blackberry
The blackberry is an edible fruit produced by many species in the genus ''Rubus'' in the family Rosaceae, hybrids among these species within the subgenus ''Rubus'', and hybrids between the subgenera ''Rubus'' and ''Idaeobatus''. The taxonomy ...
(''Rubus fruticosus''), briar (''Rosa rubiginosa
''Rosa rubiginosa'' (sweet briar, sweetbriar rose, sweet brier or eglantine; syn. ''R. eglanteria'') is a species of rose native to Europe and western Asia.
Description
It is a dense deciduous shrub 2–3 meters high and across, with the stems ...
''), serrated tussock (''Nassella trichotoma
''Nassella trichotoma'', the serrated tussock, is a type of bunchgrass plant, native in Argentina, Uruguay, Chile, and Peru.
It is on the list of Weeds of National Significance
Weeds of National Significance (WoNS) is a list of the most proble ...
''), St John's wort (''Hypericum perforatum'') and thistle
Thistle is the common name of a group of flowering plants characterised by leaves with sharp prickles on the margins, mostly in the family Asteraceae. Prickles can also occur all over the planton the stem and on the flat parts of the leaves ...
s (family Asteraceae
The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae ...
). They are particularly useful for controlling heavy weed infestations in difficult terrain. Goats have a preference for such weeds over other pasture
Pasture (from the Latin ''pastus'', past participle of ''pascere'', "to feed") is land used for grazing. Pasture lands in the narrow sense are enclosed tracts of farmland, grazed by domesticated livestock, such as horses, cattle, sheep, or sw ...
species. Control of these weeds is usually expensive and herbicide
Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...
s are not appropriate in some environments.[
]
Environmental impact
There are no documented examples of feral goats severely damaging large areas in absence of other herbivores, but they contribute their share of damage to the vegetation, soil and native fauna in areas of overgrazed pastoral land.[ Feral goats can deplete the soil's protective cover of vegetation and break up the soil crust with their hooves. This leads to ]wind erosion
Aeolian processes, also spelled eolian, pertain to wind activity in the study of geology and weather and specifically to the wind's ability to shape the surface of the Earth (or other planets). Winds may erode, transport, and deposit mate ...
during drought
A drought is defined as drier than normal conditions.Douville, H., K. Raghavan, J. Renwick, R.P. Allan, P.A. Arias, M. Barlow, R. Cerezo-Mota, A. Cherchi, T.Y. Gan, J. Gergis, D. Jiang, A. Khan, W. Pokam Mba, D. Rosenfeld, J. Tierney, an ...
s, water erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is d ...
during rain
Rain is water droplets that have condensed from atmospheric water vapor and then fall under gravity. Rain is a major component of the water cycle and is responsible for depositing most of the fresh water on the Earth. It provides water f ...
storms and can cause slips in steep areas.[ Increased erosion rates can have a significant long-term impact on ]biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variability''), species ('' species diversity''), and ecosystem ('' ecosystem diversity'') ...
through the removal of soil
Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former te ...
and nutrients, and the alteration of soil structure leading to reduction in potential productivity. Feral goats may also affect perennial vegetation by feeding on established plants and by preventing the regeneration of seedlings. These goats, by browsing, can kill established plants by defoliation
A defoliant is any herbicidal chemical sprayed or dusted on plants to cause their leaves to fall off. Defoliants are widely used for the selective removal of weeds in managing croplands and lawns. Worldwide use of defoliants, along with the ...
. They affect the regeneration processes indirectly when they reduce the ability of plants to produce seeds and directly when they eat young plants. Feral goats are particularly devastating to island ecosystems, causing direct and indirect impacts through overgrazing, which often results in ecosystem degradation and biodiversity loss
Biodiversity loss includes the worldwide extinction of different species, as well as the local reduction or loss of species in a certain habitat, resulting in a loss of biological diversity. The latter phenomenon can be temporary or permanent, de ...
.[
It has also been found that the removal of feral goats leads to a decline in introduced annual grasses and an increase in native woody perennials and introduced fire-promoting perennial grasses. So, even though the initial impact of goats is often difficult to assess, elimination of goats may lead to increases in fire frequency and further invasion by introduced grasses.
]
Impact on native fauna
Feral goats affect the native terrestrial fauna of Australia by direct competition for resources such as food, water and shelter, and by contributing to changes in ecosystems. These impacts are usually undesirable because they reduce the biodiversity of the ecosystem. Feral goats compete with domestic livestock for food and water, although dietary overlap in some habitats may be high only when food is limiting. When it comes to water, feral goats can even exclude some animals aggressively. The goats can cause water levels in rock holes to be so lowered as to exclude other animals or cause animals to fall in, drown and consequently, pollute the supply. Goat dung can be deposited around waterholes and springs to a depth of several centimeters. Dung, along with the bodies of goats that fall in water and decompose, is likely to eutrophicate the water and have a major impact on the freshwater biota. Feral goats also compete with the native animals for shelter especially in rock cave
A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...
s. They have also found to eat some invertebrates such as gall-forming and scale insects. But whether this deliberate or incidental is unknown.[
Goats are also considered a serious threat to ]yellow-footed rock-wallaby
The yellow-footed rock-wallaby (''Petrogale xanthopus''), formerly known as the ring-tailed rock-wallaby, is a member of the macropod family (the marsupial family that includes the kangaroos, wallabies, tree-kangaroos, and wallaroos).
Descripti ...
(''Petrogale xanthopus'') populations as there is considerable overlap in both species’ diet and habitat. Rock-wallaby numbers recovered after the 1983 drought in Gap Range, New South Wales where goats had been culled but concurrently failed to recover at the nearby Coturaundee Range, where goats were present in very high densities because they were not culled. Feral goats have been implicated in the decline of the brush-tailed rock-wallabies (''Petrogale penicillata'') in South Australia.
The additional grazing pressure that the feral goats apply has two consequences in relation to effects on other animals. Firstly, this will increase the amount of time when food is limiting. Secondly, goats have a more catholic diet than sheep, cattle
Cattle (''Bos taurus'') are large, domesticated, cloven-hooved, herbivores. They are a prominent modern member of the subfamily Bovinae and the most widespread species of the genus ''Bos''. Adult females are referred to as cows and adult mal ...
and kangaroo
Kangaroos are four marsupials from the family Macropodidae (macropods, meaning "large foot"). In common use the term is used to describe the largest species from this family, the red kangaroo, as well as the antilopine kangaroo, eastern gre ...
s, utilising many shrubs and trees that are unpalatable to these species. A broader ecological niche
In ecology, a niche is the match of a species to a specific environmental condition.
Three variants of ecological niche are described by
It describes how an organism or population responds to the distribution of resources and competitors (for ...
may allow goats to persist longer in droughts than their competitors and have a greater impact on their common food supply. In high numbers, and during drought, they may therefore significantly reduce the biomass
Biomass is plant-based material used as a fuel for heat or electricity production. It can be in the form of wood, wood residues, energy crops, agricultural residues, and waste from industry, farms, and households. Some people use the terms bi ...
of perennial vegetation, leading to further land degradation
Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land.
It is viewed as any change or disturbance to the land perceived to be deleterious ...
and hampering regeneration of vegetation. Goats are also a potential reservoir for a number of exotic diseases that could enter Australia, such as foot-and-mouth disease
Foot-and-mouth disease (FMD) or hoof-and-mouth disease (HMD) is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids. The virus causes a high fever lasting two to six days, followe ...
. Any attempt at eliminating a disease could therefore be frustrated by the difficulties and cost in controlling goats.
Feral goats have a more indirect impact on the native fauna as a result of their effects on the vegetation and soil. The changes to the vegetation harm some native animals, whereas benefit a few like the ones that feed on goat dung, such as termite
Termites are small insects that live in colonies and have distinct castes (eusocial) and feed on wood or other dead plant matter. Termites comprise the infraorder Isoptera, or alternatively the epifamily Termitoidae, within the order Blattode ...
s and decomposer
Decomposers are organisms that break down dead or decaying organisms; they carry out decomposition, a process possible by only certain kingdoms, such as fungi. Like herbivores and predators, decomposers are heterotrophic, meaning that they use o ...
s.[
]
Management
Management of feral goats has varied depending on the balance between their pest and resource status, and their legal definition in different states. Feral goats are mostly viewed as pests by most land managers. This has led to campaigns to manage or eradicate them. Some laws prescribe how feral goats are to be managed, while others merely define them as pests and leave management to the discretion of land owners or public agencies. State and territory governments provide legislative, technical and possibly financial support for feral goat control, and are also responsible for feral goat management on land held by their agencies.[
There is no current management policy for the control of feral goats in New South Wales.][ A group of pastoral and state agencies presented a proposal at the National workshop on Feral Goat Management. The proposal seeks to manage feral goats as part of a total grazing management program which aims to reduce the impact of goats on pastoral production and conservation values to insignificant levels. Goats are presently opportunistically mustered for slaughter.][ In New South Wales in 1996, feral goats occupied an estimated total area of 11,400 square kilometres in 101 conservation reserves. Sixty-seven of these were in the eastern, higher-rainfall areas of the State, where the impacts of feral goats have been little studies.
In Queensland, feral goats are declared pests under the Rural Lands Protection Act 1985. The widespread drought in Queensland has focused land managers' need to reduce total grazing pressure in the mulga lands. The Queensland Department of Environment and Heritage has an unwritten policy to eradicate goats from national parks, and has a program to do so from some offshore islands in cooperation with the Queensland Department of Lands.][
Feral goats are managed by the Australian Capital Territory Parks and Conservation Service when they trespass on national parks and reserves. Feral goats are not declared pests in the Territory, so their management on private land is discretionary.][
It is illegal to release goats into the wild in South Australia. Pastoral zone Soil Conservation Boards, with support from State and Commonwealth Government agencies, have embarked on a program to mitigate goat damage by promoting and coordinating goat control.][
In the Northern Territory, goats are classified as stock under the Stock Diseases Act 1994 and the Territory has no general management policy for feral goats. Feral goats are not listed as pests in the Territory Parks and Wildlife Conservation Act 1988, but this classification is under review. The lack of definition has allowed people to introduce goats to areas previously free of goats, including islands.][
Unowned goats in Tasmania are defined as feral under provisions of the Animal Health Bill and can be controlled if they present a stock disease problem.][ A survey by the Parks and Wildlife Service in 1991 led to the development of a feral goat threat abatement plan and an ongoing control campaign. By June 1995, 55 of the 136 populations located had been eradicated. Some management is done by recreational hunters and DELM has a feral goat control program on Crown land using the Judas goat technique and shooting from helicopters.][
In Victoria, feral goats are declared as 'Established Pest Animals' under the Catchment and Land Protection Act 1994. All landowners (including the Crown) must take all reasonable steps to control them. Feral goat populations appear to be small and isolated in Victoria.][
Goats are widely distributed in Western Australia, where they are regarded as a pest on rangelands. The Agriculture and Related Resources Protection Act 1976 sets out landowners' responsibilities to deal with them and to limit their spread. The principal driving force behind attempts to manage goats in the state is peer pressure among land managers. This results in community cooperation and coordination to manage goats, and legislation is only used as a means of last resort when all attempts to gain cooperation have failed. Western Australia has a feral goat management program covering most feral herds, and involves mustering goats for commercial sale to achieve the initial knockdown, followed by aerial and ground shooting to attempt to kill the remaining animals.][ The success of aerial shooting to control feral goats in arid and semi-arid environments has led to its widespread use in rugged and more densely vegetated terrain elsewhere in Australia.
Some pastoralists have also proposed establishing managed populations of feral goats for cashmere and meat production in the semiarid pastoral regions of Western Australia. Recent trials have shown that because of the high capital inputs required and low fibre yields, cashmere production in pastoral areas is not viable.] In the Australian wild, feral goats have predators like dingo
The dingo (''Canis familiaris'', ''Canis familiaris dingo'', ''Canis dingo'', or ''Canis lupus dingo'') is an ancient (Basal (phylogenetics), basal) lineage of dog found in Australia (continent), Australia. Its taxonomic classification is de ...
es, saltwater crocodile
The saltwater crocodile (''Crocodylus porosus'') is a crocodilian native to saltwater habitats and brackish wetlands from India's east coast across Southeast Asia and the Sundaic region to northern Australia and Micronesia. It has been listed ...
s, feral pig
The feral pig is a domestic pig which has gone feral, meaning it lives in the wild. They are found mostly in the Americas and Australia. Razorback and wild hog are Americanisms applied to feral pigs or boar-pig hybrids.
Definition
A feral pi ...
s, or wedge-tailed eagle
The wedge-tailed eagle (''Aquila audax'') is the largest bird of prey in the continent of Australia. It is also found in southern New Guinea to the north and is distributed as far south as the state of Tasmania. Adults of this species have lon ...
s that eat sick adults or kids.
See also
*Invasive species in Australia
Invasive species in Australia are a serious threat to the native biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic ('' genetic variabi ...
*Conservation in Australia
Conservation in Australia is an issue of state and federal policy. Australia is one of the most biologically diverse countries in the world, with a large portion of species endemic to Australia. Preserving this wealth of biodiversity is importan ...
References
{{DEFAULTSORT:Feral Goats In Australia
Invasive animal species in Australia
Feral goats
Goats
The goat or domestic goat (''Capra hircus'') is a domesticated species of Caprinae, goat-antelope typically kept as livestock. It was domesticated from the wild goat (''C. aegagrus'') of Southwest Asia and Eastern Europe. The goat is a membe ...
Fauna naturalised in Australia