Details of this species in Banks Peninsula Status: Alien
Invasiveness: Invasive
Occurrence: Present/controlled
Source: Parkes 2003 Arrival Date:
Introduction: Species Notes for this Location:
Goats (Capra hircus) were imported and farmed in substantial numbers on Banks Peninsula from 1980 onwards to control weeds (although they had been present before this time); Radcliffe (1985) reported that goats were effective controllers of gorse regeneration at high densities of 20/ha (Parkes 2003). The negative impact that the goats would have on native bush regeneration and the appropriate measures to prevent domesticated goats from escaping fenced land and reeking havoc on natural plant communities was presumably not considered. Management Notes for this Location:
In 1988 public concern at the effect of a growing number of feral goats (Capra hircus) on Banks Peninsula lead to the formation of a committee whose aim it was to encourage control of the goats; in 1990 the central government recognised Banks Peninsula as the highest national priority in terms of controlling feral goats. Of a total annual budget of $5 million dedicated to the control of goats, $82 000 was allocated to the Canterbury Conservancy to develop and put into effect a goat control plan. Between 1990 and 2003 ground control (hunting) was enacted. Helicopter control (aerial hunting) occurred in 1993/94 and from 1996 onwards. Aerial hunting appears to be much more effective in the tracking down and killing of the animals (as locating goat herds is achieved with greater time efficiency). In 1993/94, for example, only 4 hours of aerial hunting were needed to produce a result of 302 killed goats, whereas in 1994/95 200 hours of ground hunting were needed to produce the same result (Parkes 2003).
Apparently there are still about 9 herds of domestic goats (of up to 50 individuals) in the Port Hills area that are mainly utilised for weed control. The Christchurch City Council acknowledges that the goats may pose a threat to the sustainability of local flora, and are able to reach areas on rocky bluffs that provide refuges for some vulnerable plant species (McCombs Devlin and McMillan 2001). The CCC also recognises that they are particularly costly and difficult to control and contain. This implies proactive preventative measures would be more cost effective than reactionary control measures. Location Notes:
Banks Peninsula was an island until the expanding Canterbury Plains reached its base some 20 000 years ago, and thus it has some of the biotic characteristics of islands (ie: endemic species). There is a complex mosaic of communities on the peninsula including beech forest (at Hinewai), podocarp/hardwood forest (at Ahuriri), snow tussock and subalpine shrubs (Mt. Sinclair) and deciduous forest dominated by Plagianthus, Fuchsia and Aristotelia (Purple Peaks). Other important habitats include rocky hills and volcanic plugs which provide refuges for endemic plants (including Hebe lavaudiana) and low forest communities of manuka and kanuka. As well as these native communities, there exist large areas dominated by woody weeds such as gorse; and a range of productive pasture land, horticultural land and exotic forests (Parkes 2003). Impacts:
Ecosystem change: The potential impact of goat browsing on Banks Peninsula is large, as goats are able to reach all but the most inaccessible land in the area, threatening the numerous unique plant communities and endemic plants found on the peninsula (Parkes 2003).
Modification of successional patterns: Natural successional processes that occur in the unique native plant communities on Banks Peninsula may be indirectly disrupted by goat browsing (Parkes 2003).
Reduction in native biodiversity: Native plants that are particularly palatable to, and favoured by, goats on the Banks Peninsula include mahoe (Melicytus ramiflorus), pate (Schefflera digitata) and large-leaved coprosma (Parkes 2003).
Threat to endangered species: The populations of feral goats and pigs on Great Barrier Island threaten the survival of several endangered New Zealand species. These include the kokako (see Callaeas cinerea in IUCN Red List of Threatened Species) and Hochstetter’s frog (see Leiopelma hochstetteri in IUCN Red List of Threatened Species), and several plants including Mestegis apetala and Fuchsia procumbens (Parkes 1990). Last Modified: 22/05/2006 9:55:12 a.m.
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