The legacy of Big South Cape: rat irruption to rat eradication

Big South Cape Island (Taukihepa) is a 1040 ha island, 1.5 km from the southwest coast of Stewart Island/Rakiura, New Zealand. This island was rat-free until the incursion of ship rats (Rattus rattus) in, or shortly before, 1963, suspected to have been accidentally introduced via local fishing boats that moored at the island with ropes to the shore, and were used to transport the mutton birders to the island. This incursion was reported by the muttonbirders – local Iwi who harvest the young of titi (sooty shearwater, Puffinus riseus) – to the then New Zealand Wildlife Service (via the New Zealand Department of Lands and Survey). Investigation into the reports found ship rats had reached the island and had decimated the local land bird populations. Brian Bell and Don Merton attempted some of the first translocations of South Island saddleback (Philesturnus c. carunculatus), Stewart Island snipe (Coenocorypha aucklandica iredalei) and Stead’s bush wren (Xenicus longipes variabilis) with only the saddleback being successful. Extinctions of the snipe, wren and greater short-tailed bat (Mystacina robusta) were recorded. This was the first time rats were definitively recognised as the cause of extinction of native land birds and directed further debate into the impacts of rats and how to deal with them.