The eradication of Campbell Island sheep and subsequent ecological response

Abstract

: Feral sheep were eradicated from Campbell Island (Motu Ihupuku) – a National Reserve, Nature Reserve and UNESCO World Heritage Site in subantarctic New Zealand – in three distinct stages from 1970 to 1991. The sheep derived from farming attempts on the island, starting in 1895 and abandoned by 1931. The potential genetic and commercial value of the isolated sheep population meant proposed eradication plans were not wholly supported. Compromise solutions were initially implemented that required the construction of two fences, one in 1970 and one in 1984, to separate three geographic portions of the island. This separation was to facilitate staged removal of sheep and vegetation recovery in one portion of the island whilst retaining the sheep in another portion until eradication was fully committed. Sheep were largely removed by small field teams of experienced hunters using standard ground-hunting procedures in three separate operations, with follow-up operations required to remove small numbers of survivors in all three events. Approximately 7000 sheep were shot over the three operations or associated control/eradication efforts. A significant ecological response has been reported, including a recovery in range, abundance, and individual plant size for subantarctic macroforbs ( Anisotome spp., Azorella polaris , and Pleurophyllum spp.), but also for grasses ( Chionochloa antarctica and Poa spp.).