sheep

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.

Changes in vegetation from 1990 to 2000 were examined at 10 high country localities, representing four grassland types: fescue tussock (Festuca novae-zelandiae), snow tussock (Chionochloa rigida), red tussock (C. rubra), and silver tussock (Poa cita). At each locality, three treatments were established: ambient sheep+rabbit grazing, rabbit grazing only, and no grazing. The mutivariate methods of classification and ordination were used on individual-quadrat cover data to define vegetation states and to examine transitions between them over time.

Sheep introduced to Campbell Island in 1895 for farming reached numbers of over 8000 in 1916 then declined to 1000 by 1961 (exponential growth rate r = -0.05 p.a.). Numbers increased to around 3000 from 1961 to 1969 (r = 0.14 p.a.). The island was divided into halves by a fence in 1970, and all sheep north of it were killed. The southern population continued to grow from 1970 to 1984 (r = 0.053 p.a.). The southern half of the island was cleared of sheep in 1984 except for about 800 fenced off on a peninsula.