The next frontier: assessing the feasibility of eradicating mammalian pests from Auckland Island

Auckland Island, the fifth largest island in New Zealand, is the only island in New Zealand’s subantarctic region where introduced mammalian pests remain (pigs, Sus scrofa; mice, Mus musculus; cats, Felis catus). The island has unique biodiversity and is a key site for progressing New Zealand’s goal to be free of several introduced predators by 2050. Recent island eradication successes have rekindled interest in eradicating pests from Auckland Island, and for the first time considering all three pests in one project.

Introduction, rescue, and subsequent history of Auckland Islands livestock

Farm livestock and other animals were introduced onto the Auckland Islands during the 19th century. Most were eradicated by the late 20th century, but before then, some goats (Capra aegagrus hircus), rabbits (Oryctolagus cuniculus), cattle (Bos taurus) and pigs (Sus scrofa) that were considered to have unique genetic characteristics were taken to mainland New Zealand with a view to studying and maintaining their particular breeds.

Secondary and tertiary poisoning risks associated with brodifacoum

The field use of brodifacoum baits (Talon(R) and Pestoff(R)) to control brushtail possums (Trichosurus vulpecula) has increased in recent years. This has raised concerns of secondary and tertiary poisoning, resulting from the transfer of this toxicant through the food chain. In New Zealand, feral pigs (Sus scrofa) are known to scavenge possum carcasses and and may also gain access to bait stations containing possum baits. We have determined the concentrations of brodifacoum in muscle and liver tissue from captive pigs after primary and secondary poisoning.

Vegetation Changes Induced over 10 Years by Goats and Pigs at Port Ross, Auckland Islands (Sub-Antarctic)

Marked sites established around Port Ross in 1973 were re-examined in 1983 to measure changes in the vegetation and assess the impact of goats and pigs. Goats had not increased in numbers, nor extended beyond their earlier range, but they were seen higher on the Hooker Hills. Pigs were scarce, but their sign was seen throughout. Photopoints and numerical methods both showed that Chionochloa antarctica tussock was eliminated or greatly reduced where goats and pigs occurred together, and where only pigs were present it was reduced slightly.