Competition and habitat degradation by feral goats (Capra hircus) - key threatening process listing

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Feral Goats, Capra hircus Linnaeus 1758, are descended from domestic stock introduced to Australia at various times since 1788 (Henzell 2000). Feral Goats are distinguished from domestic goats by not being permanently restrained by fences or subject to husbandry (Environment Australia 1999). 'Competition and land degradation by Feral Goats' is currently listed as a key threatening process under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999.

2. Feral Goats occur in most regions of Australia, with the majority of their distribution in the arid and semi-arid pastoral regions of Queensland, Western Australia, South Australia and NSW (Parkes et al. 1996). Dingos and Feral Dogs are their chief predators and, where wild dogs are not actively controlled, they have been observed to limit the distribution of Feral Goats (Parkes et al. 1996).

3. Feral Goats are versatile generalist herbivores (Harrington 1986). They will browse shrubs and trees, graze forbs and grass, and eat fallen fruit capsules, bark and other dead plant material (Dawson et al. 1975; Squires 1980; Dawson and Ellis 1996). Feral Goats appear to have a high taste threshold for compounds in many trees and shrubs normally unpalatable to other herbivores (Henzell 1993) and can survive on fibrous herbage with low levels of nutrients (Doyle et al. 1984). When green foliage is abundant, Feral Goats obtain sufficient water from their food, but during summer and in drought they require drinking water (Dawson et al. 1975; Parkes et al. 1996).

4. Feral Goats have a high reproductive potential. Females attain sexual maturity at around six months of age and produce one to three kids every eight months (Henzell 2000), or twice every 12 months under favourable conditions (Menkhorst 1995). In the absence of control, Feral Goat populations can increase by up to 75% per year (Henzell 2000).

5. Feral Goats are usually sedentary when feed is available but are capable of moving large distances when feed is limited (Henzell 2000) e.g. a home range of almost 600km2 was estimated for an individual goat in a pastoral area of Western Australia (King 1992). Feral Goat movement patterns vary according to topography, harvesting pressure and feed availability (Freudenberger and Barber 1999). Individuals move freely through most fences in pastoral areas and are able to reinvade areas from which they have previously been removed. Feral Goats can also utilise many areas that are inaccessible to other large herbivores e.g. rocky slopes and cliff lines.

6. Feral Goats present a potential threat to plant communities given the large number of plant species that are palatable to them and their ability to browse and graze in inaccessible areas such as in trees or in dense thickets (Squires 1980; Henzell 1993; Parkes et al. 1996). Landsberg and Stol (1996) found that Feral Goats contribute substantially to total grazing pressure in the woody rangelands of NSW, and that they probably have the greatest potential for causing grazing impacts in the region. Moreover, the ability of Feral Goats to survive on low nutrient fibrous vegetation (Doyle et al. 1984) enables them to continue to feed under adverse environmental conditions, e.g. Wilson and Mulham (1980) found that goats demonstrated a superior ability to survive in competition with sheep during drought, and this was attributed to the ability of goats to browse higher on trees and their willingness to eat fallen leaves. In one study of the impacts of sheep and goat grazing, Feral Goats were not identified as a threat to the regeneration of plant species in chenopod shrublands in South Australia (Tiver and Andrew 1997). However, enclosure experiments have demonstrated the species' potential to overgraze and prevent regeneration of plants (Harrington 1979; Harrington 1986). Such overgrazing is likely to be prevalent during drought or in concert with other introduced herbivores such as rabbits, Oryctolagus cuniculus (Henzell 2000). Moreover, the floristic composition of plant communities may be altered as a result of intense browsing by Feral Goats (Harrington 1986).

7. Feral Goats can cause significant habitat degradation. Removal or destruction of vegetation together with trampling by ungulate herbivores decreases soil stability and contributes to erosion (Henzell 1993; Eldridge 1998). An experiment in the Macleay River gorge system, northeastern NSW, demonstrated that removal of goats resulted in a rapid decrease in soil erosion; this initial rapid decrease was followed by a slower decline in erosion coincident with a relative increase in vegetation (Bayne et al. in press). Further, a study of high-intensity goat grazing in dunefields northwest of Cobar, northwestern NSW, found that goat grazing rapidly depleted perennial grasses and shrubs and caused the soil surface to become highly susceptible to wind erosion (Green et al. 1998).

8. Feral Goat activity can significantly alter the habitat of native fauna and flora e.g. accumulated Feral Goat droppings may degrade the habitat of the endangered Broad-headed Snake, Hoplocephalus bungaroides (Murphy 1996); and deposition of goat droppings around waterholes and springs are likely to eutrophy the water and thus affect freshwater biota (Parkes et al. 1996). Feral Goats trample spinifex clumps while grazing seed heads (Maher et al. 1995) and this degrades the habitat of spinifex-dependent lizard species e.g. the endangered Mallee Slender Blue-Tongue Lizard, Cyclodomorphus melanops elongata, and the endangered Marble-faced Delma, Delma australis. Further, trampling by Feral Goats was recognised as a threat to the Endangered Artesian Springs Ecological Community, and the Endangered sedge Eriocaulon carsonii (Pickard 1992).

9. Feral Goats may compete with native fauna for food, water and shelter. In particular competition from Feral Goats has been implicated as a threat to the endangered Yellow-footed Rock-wallaby, Petrogale xanthopus (Lim 1987) and the endangered Brush-tailed Rock-wallaby, P. penicillata (NSW NPWS 2001). There also exists unpublished reports of goat musters correlating with the rapid recovery of Yellow-footed Rock-wallabies following drought (Henzell 1990). However, competition between Feral Goats and rock-wallabies is yet to be demonstrated. Given that goats consume the highly digestible, nitrogen rich parts of plants, and when available, growing tips, fruit and seeds, it is likely that they would reduce the amount of nutritious plant material available to other herbivores. Thus, the capacity of rock-wallabies to respond to improved seasonal conditions following drought might be reduced by the impact of Feral Goats (Henzell 1990).

10. The following threatened species and ecological communities are known or are likely to be threatened by Feral Goats:

11. In view of the above the Scientific Committee is of the opinion that Competition and habitat degradation by Feral Goats, Capra hircus Linnaeus 1758, adversely affects more than two threatened species, populations or ecological communities, or could cause species, populations or ecological communities that are not threatened to become threatened.

Associate Professor Paul Adam
Chairperson
Scientific Committee

Proposed Gazettal date: 12/11/04
Exhibition period: 12/11/04 - 24/12/04

References:

Bayne P, Harden R, Davies I (in press) Feral goats (Capra hircus L.) in the Macleay River gorge system, North-eastern NSW, Australia. I. Impacts on soil erosion. Wildlife Research.

Dawson TJ, Denny MJS, Russell EM, Ellis B (1975) Water use and diet preferences of free ranging kangaroos, sheep and feral goats in the Australian arid zone during summer. Journal of Zoology 177, 1-23.

Dawson TJ, Ellis BA (1996) Diets of mammalian herbivores in Australian arid, hilly shrublands: seasonal effects on overlap between euros (hill kangaroos), sheep and feral goats, and on dietary niche breadths and electivities. Journal of Arid Environments 34, 491-506.

Doyle PT, Egan JK, Thalen AJ (1984) Intake, digestion, and nitrogen and sulfur retention in Angora goats and Merino sheep fed herbage diets. Australian Journal of Experimental Animal Husbandry 24, 165-169.

Eldridge DJ (1998) Trampling of microphytic crusts on calcareous soils and its impact on erosion under rain-impacted flow. Catena 33, 221-239.

Environment Australia (1999) 'Threat abatement plan for competition and land degradation by Feral Goats.' Environment Australia, Canberra.

Freudenberger D, Barber J (1999) Movement patterns of feral goats in a semi-arid woodland in eastern Australia. Rangelands Journal 21, 71-81.

Green RSB, Nettleton WD, Chartres CJ, Leys JF, Cunningham RB (1998) Runoff and micromorphological properties of a grazed haplargid, near Cobar, NSW, Australia. Australian Journal of Soil Research 36, 87-108.

Harrington GN (1979) The effects of Feral Goats and sheep on the shrub populations in a semi-arid woodland. Australian Rangelands Journal 1, 334-345.

Harrington GN (1986) Herbivore diet in a semi-arid Eucalyptus populnea woodland. 2. Feral Goats. Australian Journal of Experimental Agriculture 26, 423-429.

Henzell R (1990) Feral Goats and Yellow-footed Rock-wallabies. In 'Proceedings of the Yellow-footed Rock-wallaby Management Workshop'. Port Augusta. (Ed. P. Copley) p. 1-6. (South Australian National Parks and Wildlife Service: Norwood, SA)

Henzell R (1993) The ecology of Feral Goats. In 'Proceedings of the national workshop on Feral Goat management: planning for action'. (Ed. D. Freudenberger) pp. 9-16. (Bureau of Resource Sciences: Canberra)

Henzell R (2000) Goat Capra hircus Linnaeus 1758. In 'The Mammals of Australia'. (Ed. R Strahan) pp. 728-30. (Reed Books: Sydney)

King D (1992) Home ranges of feral goats in a pastoral area in Western Australia. Wildlife Research 19, 643-649.

Landsberg J, Stol J (1996) Spatial distribution of sheep, feral goats and kangaroos in woody rangeland paddocks. Rangelands Journal 18, 270-291.

Lim TL (1987) Ecology and management of the rare yellow-footed rock wallaby Petrogale xanthopus, Gray 1854 (Macropodidae). PhD thesis, Macquarie University, Australia.

Maher M, Norris D, Ridge T, Robinson M (1995) 'The Ledknapper Spinifex: its people, plants and animals.' (Land Information Centre: Bathurst)

Menkhorst PW (1995) Goat Capra hircus Linnaeus 1758. In 'Mammals of Victoria: distribution, ecology and conservation'. (Ed. PW Menkhorst) pp. 261-262. (Oxford University Press: Melbourne)

Murphy MJ (1996) A possible threat to the Broad-headed Snake Hoplocephalus bungaroides: degradation of habitat by the Feral Goat Capra hircus. Herpetofauna 26, 37-38.

NSW NPWS (2001) 'Warrumbungle Brush-tailed Rock-wallaby population draft recovery plan.' NSW National Parks and Wildlife Service, Dubbo.

Parkes J, Henzell R, Pickles G (1996) 'Managing vertebrate pests: Feral Goats.' (Australian Government Publishing Service: Canberra)

Pickard J (1992) 'Conservation research statement: Eriocaulon carsonii.' Australian National Parks and Wildlife Service, Canberra.

Squires VR (1980) Chemical and botanical composition of the diets of oesophageally fistulated sheep, cattle and goats in a semi-arid Eucalyptus populnea woodland community. Australian Rangelands Journal 2, 94-103.

Tiver F, Andrew MH (1997) Relative effects of herbivory by sheep, rabbits, goats and kangaroos on recruitment and regeneration of shrubs and trees in eastern South Australia. Journal of Applied Ecology 34, 903-914.

Wilson AD, Mulham WE (1980) Vegetation changes and animal productivity under sheep and goat grazing on an arid Belah (Casuarina cristata) - Rosewood (Heterodendrum oleifolium) woodland in western New South Wales. Australian Rangelands Journal 2, 183-188.