Goat (feral or wild)
|Common name:||goat (feral or wild)|
|Scientific name:||Capra hircus|
This species is an established pest animal (feral or wild populations only) in the state of Victoria.
History of spread
Nineteen domestic goats originally landed with the First Fleet at Sydney in 1788. By 1790 there were approximately 1900 goats in the colony and they quickly spread across Australian settlements.
Goats were introduced to inland areas by early settlers, miners and railway construction gangs who used them for meat and milk. Goats were taken to Phillip Island in the early 1800s to provide sport and food. Goats were widespread in Tasmania by the 1820s and arrived in South Australia in 1836.
Cashmere and Angora goats were introduced to Australia in the mid 1800s to start a fibre industry. When this industry collapsed in the 1920s, many pastoralists abandoned their goats in preference for wool.
The mixed origins of feral goats are reflected in the genetic diversity seen in wild populations.
Distribution in Victoria
There is little information available regarding the distribution and density of feral goats in Victoria. However, anecdotal information suggests that the largest goat populations occur in areas where very large tracts of forested or semi arid areas offer some protection from control and people.
Examples of these areas include the Grampians National Park (NP), Little Desert NP, Hattah Kulkyne NP, Murray Sunset NP and Alpine NP. Feral goats have also been sighted in many other state and regional parks and forests throughout Victoria.
The feral goat is a sub-species of goat descended from the wild goats of southwest Asia. The goat is a member of the Bovidae family and is closely related to the sheep; both are in the goat-antelope sub-family Caprinae.
There are over three hundred distinct breeds of goat. The present Australian feral goat population is a mix of Angora, Cashmere, Anglo-Nubian, British Alpine, Saanen and Toggenburg breeds.
Both male and female goats have distinctive curved or corkscrew shaped horns, although some breeds of goats may be hornless. The coats of feral goats vary widely depending on breed including many colours and patterns. Again, depending on breed, the hair of the goat may be short, long, curled, silky or coarse. Goats may have wattles (hanging fleshy lobes) on the neck and beards. Goats may have straight or rounded noses.
An adult male goat is called a buck, the female is called a doe and juvenile goats are referred to as kids. Colloquially, an adult male may be referred to as a 'billy' and an adult female as a 'nanny'. An adult goat weighs 40-60 kgs while kids weigh about 2.6 kgs at birth. Male kids are heavier than female kids and this is a difference that they retain throughout their lives.
Feral goats are highly sociable animals and form family units consisting of an adult female goat and her recent offspring. Family social units associate together to form a herd.
Male kids leave their mothers and form 'bachelor' herds with similar aged males. Feral goat bachelor herds overlap with the female's home range during breeding periods but may range over much larger areas during the rest of the year. Feral goat home ranges can vary from one square kilometre when water and food are abundant, and up to 600 square kilometres for an adult male when resources are scarce.
Female goats leave the group to give birth in a protected place such as a rock overhang cave or dense vegetation. Goat kids are capable of following their mothers soon after birth however many are hidden for the first few days and only visited by their mothers for feeding.
Feral goats are most active during the day and rest at night in regular camp sites. Herd dynamics are variable depending on seasonal changes, birth rates and the movements of the male bachelor herds. Feral goats tend to use high or difficult-to-access areas as their night time camp sites to minimise the risk of predation.
Feral goats use smell over sight to find food and detect predators. Goats have around one third of the visual distance capacity of a human. The eyes are prominent which gives goats a large panoramic field of 320-340 degrees. Goats prefer to graze facing into the wind in order to detect scent using their well developed sense of smell.
The frequency at which goats drink water is influenced by environmental conditions. Goats are reliant on access to water and their home range will revolve around this requirement. Generally a herd of feral goats is led by a dominant male. He shares leadership with a dominant female who will usually outlast several dominant males throughout her time.
Amongst the male goats, horn size can suggest dominance without physical fighting. Adult male goats are also highly reliant on scent to indicate dominance and physical condition. Male goats are known to urinate on their own beards; this practice is thought to accentuate their own scent imparting dominance over other goats. Adult male goats display dominance through a variety of contact and non-contact methods. Non-contact threats include staring, facing a rival with the chin down and horns forward, rushing or rearing. Encounters where physical contact occurs include pushing, head butting, engaging horns and rearing up and clashing.
Feral goats are highly social animals and have reasonably complex systems of communication which includes smell, sight and sound. Alarm behaviour in feral goats is highly developed, making it difficult to drive goats as they scatter when faced with danger. When a female goat detects danger, she will stand rigid with ears towards the source of alarm. Kids respond by running to the relative safety of the female. Female goats may also snort loudly and repeatedly to alert nearby goats to the danger. Depending on the threat, the group may flee, move away slowly, or return to their previous activities.
Feral goats are opportunistic browsers who will generally select the highest quality plant food available. They will eat grass, leaves, twigs, bark, flowers, fruit, roots, plant litter, seeds and fungi. Despite their tendency to select high quality foods, they are capable of eating most plant species in Australia including many plants which are toxic, spiny and bitter, which sheep and cattle are likely to avoid.
Availability of water limits feral goat distribution to where water occurs or is artificially provided, for example by stock watering points. An average sized goat requires between 2 to 4.5 litres of water per day depending on temperature. Despite this, some goats in cooler and wetter climates are able to obtain the majority of their water requirements from their food which means that they are capable of surviving in areas with limited permanent fresh water.
Feral goats will establish in any area where food, water and protection from predators is available. In Victoria, feral goats tend to be able to establish and maintain populations in the semi-arid environments of the North West and the mountainous terrain of the Grampians, Alpine and East Gippsland regions.
In mountain regions feral goats can live at high altitudes where there is food and water available. Goats are skilled rock and log climbers and regularly use caves and rock overhangs for shelter.
Wild dogs and dingoes are the most significant predators of feral goats in Australia. Feral pigs, crocodiles, foxes and large eagles may also prey upon feral goats, in particular feral goat kids.
Diseases and parasites
Feral goats are susceptible to many devastating exotic livestock diseases that are not present in Australia including foot-and-mouth disease, scrapie, rinderpest, Rift Valley fever, rabies and blue tongue.
Feral goats are susceptible to a number of diseases currently found in Australia including Johne's Disease, Q fever, tetanus, leptospirosis, hydatids, pulpy kidney, blackleg, and various parasitic worms of the gastro-intestinal tract.
Feral goats may act as a vector in the spread of disease to domestic sheep and goat herds.
All domestic and feral goats come from common ancestors which traditionally had a breeding season spanning two to three months over the autumn to winter period. Current populations of feral goats can breed all year round; however there still tends to be a peak in breeding during autumn with less in spring.
Feral goat breeding is influenced by environmental factors including drought, population dynamics, food and water availability. Despite variations in breeding seasons, all sexually mature female goats commonly come into oestrus at about the same time.
As many populations of feral goats have a higher proportion of females than males, population growth can be high. It is generally accepted that, with the absence of human influence or control, a population has the potential to double in size every 1.6 years. Female goats are sexually mature from six months of age. Feral goats can produce young twice a year as they are capable of becoming pregnant soon after giving birth and their gestation period is only 150 days. Twins and triplets are relatively common in both domestic and feral goat populations however the average litter size is approximately 1.6.
The dispersal of feral goats depends on availability of food, water and shelter. Feral goats tend to prefer to maintain a small home range and traditional camp sites where possible; males in particular will disperse when food and water resources are limited. Young female goats will stay with their female family group throughout their lives while males will leave these groups at puberty and join bachelor groups.
From day to day, feral goats may demonstrate what is known as '"fission-fusion'" patterns of dispersal, that is, a relatively large herd will separate into sub groups during the day and re-unite at a common camp site at night.
Most breeding of feral goats occurs in autumn, however breeding can occur all year.
Females can give birth twice a year and produce one to three kids per litter.
Natural mortality of kids from birth to six months can be as high as 35 per cent while in adults this figure drops to an estimated ten percent. Human induced factors have been known to increase kid mortality to 45 per cent.
Female goats can become pregnant at six months of age.
Feral goats can live for a maximum of 16 years.
Impact on ecosystems and waterways
Feral goats cause considerable environmental impacts in Victoria. Feral goats cause land degradation through soil damage, over grazing and strip browsing. The soil's crust and its protective cover of vegetation are disturbed through trampling by the goat's hooves.
As a selective browser, feral goats can impact on specific plant communities over a relatively short period. Feral goat populations affect long lived plants by eating established plants and preventing the recruitment and growth of seedlings. Goats are capable of climbing trees where branches and trunks are on suitable angles, enabling them to graze much higher than a kangaroo or sheep. Even when adult trees are able to survive, due to the presence of foliage that goats cannot reach, the goats can destroy seedlings affecting the rate of recruitment, which can limit the survival of that plant community.
Feral goats can impact on terrestrial native animals. Goats compete with many animals species for food, water and shelter. Goat dung around water ways, together with goat carcasses that have fallen into the water, is likely to affect water quality.
The impacts of feral goats on native animals have not been measured in Victoria.
Agricultural and economic impacts
Feral goats are a major environmental and agricultural pest throughout Australia. Competition and land degradation by feral goats is listed as a key threatening process under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act).
Economic losses as a result of the impact of feral goats can be split into four areas: costs to primary production; costs associated with exotic diseases; costs of land degradation caused by goats; and costs to the public to manage goats.
In other Australian states some costs are re-couped through the mustering and commercial exploitation of feral goats, however due to lower numbers and difficult terrain this is generally not practiced in Victoria.
The monetary value of economic losses in Victoria is unknown, however the cost to Australia as a whole is estimated at up to $25 million per annum. While the largest populations of feral goats occur in Western Australia, South Australia and New South Wales, there are still considerable populations in Victoria, many of which inhabit mountainous areas where they are very difficult and therefore costly to control.
While feral goats are found mostly on public land in Victoria, they are also found on private property. Feral goats and domestic livestock have overlapping diets and habitats which can cause competition with domestic livestock for food, water and shelter. Feral goats are capable of out-competing and outlasting both sheep and kangaroos in time of drought.
Primary producers who own domestic goats may incur costs through having to prevent male feral goats from mating with their females. Foresters also incur costs to production caused by goat damage to their seedlings.
Feral goats are known to be susceptible to several diseases of livestock including Ovine Johne's Disease, foot-and-mouth, rinderpest, rabies and blue tongue. Unchecked wild herds could potentially play a major role in the spread of disease and act as a reservoir for these and other livestock diseases if diseases are introduced into Australia.
Recommended control measures
The Department of Economic Development, Jobs, Transport and Resources (DEDJTR) recommends integrated pest management using all available control measures implemented in a coordinated manner at a landscape scale.
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- Feral Goat fact sheet. 2010. Biosecurity Queensland. Accessed on 13th February 2012 http://www.dpi.qld.gov.au/documents/Biosecurity_EnvironmentalPests/IPA-Feral-Goat-PA18.pdf
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- The Feral Goat Fact Sheet. 2011. Department of Sustainability Environment Water Population and Communities. Accessed on 13th February 2012