Feral goat

Feral goat

The feral goat is the domestic goat when it has become established in the wild. Feral goats occur in Australia, New Zealand, Ireland, Great Britain, Hawaii, the Galapagos and in many other parts of the world...

s are an invasive animal species in Australia

Australia

Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...

.

History

Goats originally came to Australia with the First Fleet

First Fleet

The First Fleet is the name given to the eleven ships which sailed from Great Britain on 13 May 1787 with about 1,487 people, including 778 convicts , to establish the first European colony in Australia, in the region which Captain Cook had named New South Wales. The fleet was led by Captain ...

 in 1788. These goats were the ancestors of the feral goat populations present in Australia today. During the 19th Century, the goats were set free by mariners as a measure to ensure emergency supplies of food. However, most feral goat populations have a domestic origin. 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

Australian Capital Territory

The Australian Capital Territory, often abbreviated ACT, is the capital territory of the Commonwealth of Australia and is the smallest self-governing internal territory...

 but are rare in the Northern Territory

Northern Territory

The Northern Territory is a federal territory of Australia, occupying much of the centre of the mainland continent, as well as the central northern regions...

. 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

Lord Howe Island

Lord Howe Island is an irregularly crescent-shaped volcanic remnant in the Tasman Sea between Australia and New Zealand, directly east of mainland Port Macquarie, and about from Norfolk Island. The island is about 11 km long and between 2.8 km and 0.6 km wide with an area of...

, and islands in the Archipelago of the Recherche

Archipelago of the Recherche

Archipelago of the Recherche is a group of 105 islands, and over 1200 "obstacles to shipping", off the southern coast of Western Australia. The islands, also known as the Recherche Archipelago, stretch from East to West and to off-shore....

. Island populations are generally considered to be pests but the feral goats on North Goulburn Island

Goulburn Islands

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 the North and South Goulburn Islands. The Warruwi Aboriginal people are the traditional owners of the Goulburn Islands....

 provide a source of trophy animals for a safari

Safari

A safari is an overland journey, usually a trip by tourists to Africa. Traditionally, the term is used for a big-game hunt, but today the term often refers to a trip taken not for the purposes of hunting, but to observe and photograph animals and other wildlife.-Etymology:Entering the English...

 operation run by the Aboriginal

Australian Aborigines

Australian Aborigines , also called Aboriginal Australians, from the latin ab originem , are people who are indigenous to most of the Australian continentthat is, to mainland Australia and the island of Tasmania...

 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

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 Wooramel River on the eastern shore of Shark Bay...

, Bernier Island

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.It was a hospital location in the early 1900s....

, 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

South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...

 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 colonization 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 $

Aud

Aud might refer to*Australian dollar *Ambedkar University, Delhi *American University in Dubai *Doctor of Audiology *Auðr, the son of Nótt and Naglfari in Norse mythology...

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.

On the positive side, 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

The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...

n Boer goat

Boer goat

The Boer goat was developed inSouth Africa in the early 1900s for meat production. Their name is derived from the Dutch word "Boer" meaning farmer. The Boer goat was probably bred from the indigenous goats of the Namaqua Bushmen and the Fooku tribes, with some crossing of Indian and European...

 to produce a heavier animal for export.

Feral goats are also used as a biological method of controlling weed

Weed

A weed in a general sense is a plant that is considered by the user of the term to be a nuisance, and normally applied to unwanted plants in human-controlled settings, especially farm fields and gardens, but also lawns, parks, woods, and other areas. More specifically, the term is often used to...

s such as blackberry

Blackberry

The blackberry is an edible fruit produced by any of several species in the Rubus genus of the Rosaceae family. The fruit is not a true berry; botanically it is termed an aggregate fruit, composed of small drupelets. The plants typically have biennial canes and perennial roots. Blackberries and...

 (Rubus fruticosus), briar (Rosa rubiginosa), serrated tussock (Nassella trichotoma

Nassella trichotoma

Nassella trichotoma is a type of bunchgrass plant, native in Argentina, Uruguay, Chile, and Peru.It is considered a weed of national significance in Australia, reducing the productivity of pasture and creating a fire hazard. In many states, landowners are required by law to keep their land free of...

), St John's wort

St John's wort

St John's wort is the plant species Hypericum perforatum, and is also known as Tipton's Weed, Chase-devil, or Klamath weed....

 (Hypericum perforatum) and thistle

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 often occur all over the plant – on surfaces such as those of the stem and flat parts of leaves. These are an adaptation that protects the...

s (family Asteraceae

Asteraceae

The Asteraceae or Compositae , is an exceedingly large and widespread family of vascular plants. The group has more than 22,750 currently accepted species, spread across 1620 genera and 12 subfamilies...

). They are particularly useful for controlling heavy weed infestations in difficult terrain. Goats have a preference for such weeds over other pasture

Pasture

Pasture 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 swine. The vegetation of tended pasture, forage, consists mainly of grasses, with an interspersion of legumes and other forbs...

 species. Control of these weeds is usually expensive and herbicide

Herbicide

Herbicides, also commonly known as weedkillers, are pesticides used to kill unwanted plants. Selective herbicides kill specific targets while leaving the desired crop relatively unharmed. Some of these act by interfering with the growth of the weed and are often synthetic "imitations" of plant...

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 during drought

Drought

A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...

s, water erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 during rain

Rain

Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...

 storms and can cause slips in steep areas. Increased erosion rates can have a significant long-term impact on biodiversity

Biodiversity

Biodiversity is the degree of variation of life forms within a given ecosystem, biome, or an entire planet. Biodiversity is a measure of the health of ecosystems. Biodiversity is in part a function of climate. In terrestrial habitats, tropical regions are typically rich whereas polar regions...

 through the removal of soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 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. 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.

It has also been found that the removal of feral goats lead 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

Cave

A cave or cavern is a natural underground space large enough for a human to enter. The term applies to natural cavities some part of which is in total darkness. The word cave also includes smaller spaces like rock shelters, sea caves, and grottos.Speleology is the science of exploration and study...

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

Yellow-footed Rock-wallaby

The Yellow-footed Rock-wallaby is a member of the macropod family ....

 (Petrogale xanthopus) populations as there is considerable overlap in both species’ diet and habitat. It has been claimed that 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 pencillata) 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

Cattle are the most common type of large domesticated ungulates. They are a prominent modern member of the subfamily Bovinae, are the most widespread species of the genus Bos, and are most commonly classified collectively as Bos primigenius...

 and kangaroo

Kangaroo

A kangaroo is a marsupial from the family Macropodidae . In common use the term is used to describe the largest species from this family, especially those of the genus Macropus, Red Kangaroo, Antilopine Kangaroo, Eastern Grey Kangaroo and Western Grey Kangaroo. Kangaroos are endemic to the country...

s, utilizing many shrubs and trees that are unpalatable to these species. A broader ecological niche

Ecological niche

In ecology, a niche is a term describing the relational position of a species or population in its ecosystem to each other; e.g. a dolphin could potentially be in another ecological niche from one that travels in a different pod if the members of these pods utilize significantly different food...

 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

Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....

 of perennial vegetation, leading to further land degradation 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

Foot-and-mouth disease or hoof-and-mouth disease is an infectious and sometimes fatal viral disease that affects cloven-hoofed animals, including domestic and wild bovids...

. 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

Termite

Termites are a group of eusocial insects that, until recently, were classified at the taxonomic rank of order Isoptera , but are now accepted as the epifamily Termitoidae, of the cockroach order Blattodea...

s and decomposer

Decomposer

Decomposers are organisms that break down dead or decaying organisms, and in doing so carry out the natural process of decomposition. Like herbivores and predators, decomposers are heterotrophic, meaning that they use organic substrates to get their energy, carbon and nutrients for growth and...

s.

Management

High density populations of goats in accessible, semi-arid areas are best reduced initially by mustering or trapping at water so that the costs of control can be offset by the sale of the captured goats. To further reduce the population, or where the density of goats is too low to be economically harvested, aerial or ground shooting is an efficient method. Aerial shooting from helicopters is a good method in difficult terrain or at low goat densities. Fences have also been used to exclude goats from some areas.

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 kilometers 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

Dingo

The Australian Dingo or Warrigal is a free-roaming wild dog unique to the continent of Australia, mainly found in the outback. Its original ancestors are thought to have arrived with humans from southeast Asia thousands of years ago, when dogs were still relatively undomesticated and closer to...

es, saltwater crocodile

Saltwater Crocodile

The saltwater crocodile, also known as estuarine or Indo-Pacific crocodile, is the largest of all living reptiles...

s, razorback

Razorback

Razorback is an Americanism, loosely applied to any type of feral pig or wild boar in North America. The term has also appeared in Australia, to describe said animals in that country.-Introduction to the Americas:...

s, or wedge-tailed eagle

Wedge-tailed Eagle

The Wedge-tailed Eagle , sometimes known as the Eaglehawk in its native range, is the largest bird of prey in Australia, but it is also found in southern New Guinea. It has long, fairly broad wings, fully feathered legs, and an unmistakable wedge-shaped tail...

s that eat sick adults or kids.