A flock of approximately 4,000 domestic sheep left behind on remote Campbell Island in 1931 grew wild and developed unusual hereditary adaptations over decades without human intervention, according to a report by The Times of India.
The animals were abandoned on the subantarctic New Zealand territory when farmer John Warren, the last agricultural tenant on the island, was forced to cease operations during the Great Depression.
Warren and his workers spent about two years on the island before evacuation in 1931 due to falling meat and wool prices alongside severe supply logistics issues. The departing farm workers left approximately 4,000 sheep and between 20 and 30 cows to fend for themselves.
Campbell Island is situated approximately 620 kilometres south of Stewart Island. The remote location features harsh climatic conditions including strong winds, constant high moisture, and acidic peat soils that presented extreme survival challenges for domestic livestock.
Evolution of the feral flock
Without human care, selective breeding, or wool shearing, natural selection gradually reshaped the isolated population. Although the flock shrank to around 1,000 animals by 1961, the population rebounded during the 1960s to reach roughly 3,000 sheep.
Scientific investigations revealed that by 1970 the feral sheep had increased their lambing rates and learned to reproduce at just one year of age. The flock had also developed the capacity to shed their wool naturally, removing their reliance on regular human shearing.
Conservation and rescue efforts
Despite the scientific value of the population, the large number of feral sheep began causing severe damage to the island's unique native vegetation. Authorities erected a fence on Campbell Island in 1970 and subsequently initiated a program to gradually remove the animals.
Scientists determined to preserve the unusual lineage captured ten sheep during the summer of 1975 to 1976 and transported them to mainland New Zealand for captive breeding. According to the Te Ara encyclopedia, tests showed these sheep possessed natural resistance to foot rot as well as fleece shedding capabilities.
All remaining sheep on Campbell Island were later eradicated as part of an environmental conservation program, allowing the island's unique flora to recover. The descendants of the ten rescued sheep continue to preserve the genetic heritage of a population that evolved for nearly half a century without human intervention.
