Non-Target Species Management for the Macquarie Island Pest Eradication Project

Abstract

Author(s): Springer, Keith; Carmichael, Noel | Abstract: Mitigation of non-target species impacts is a key challenge of the Macquarie Island Pest Eradication Project (MIPEP). The project aims to eradicate rodents and European rabbits from sub-Antarctic Macquarie Island through the aerial application of cereal-based brodifacoum bait, followed by a hunting program targeting surviving rabbits. Aerial baiting was attempted in winter 2010 but postponed due to sustained adverse weather that suspended helicopter operations. Following limited baiting in 2010 (10% of the island), non-target mortality of 960 individuals across 6 (of 27) seabird and duck species was recorded. In response, the Australian and Tasmanian governments conducted a review of the project. The review established that some species would be adversely affected by the project in the short-term, but that the island’s ecosystem and most other island species would substantially benefit from pest eradication, confirming the assessments in the Environmental Impact Statement prepared prior to the operation. Enhanced mitigation measures were recommended to minimise non-target species impacts. Of several potential mitigation measures assessed, two principal measures were adopted: releasing Rabbit Haemorrhagic Disease Virus to reduce the rabbit population prior to baiting, thus minimising the number of rabbit carcasses containing poison residues available for consumption by scavengers; and increasing the effort of field teams during and after baiting to remove carcasses (the primary 2010 strategy), in an attempt to minimise the exposure of scavengers to toxic residues. Baiting resumed in May 2011 and two island-wide drops were completed by July 2011. Seabird mortality was monitored, with over 1,460 dead birds of the same species found that were affected in 2010, primarily scavenging seabirds such as kelp gulls, giant petrels, and skua. No species was considered to have sustained impacts that threatened the viability of the local population. King penguin colonies were closely monitored during helicopter over-flights and only minor and transitory impacts were observed. Wandering albatross nests were cleared of bait and chicks were not affected. No marine mammal impacts were recorded. If successful, the MIPEP will be the largest and most complex sub-Antarctic island rabbit and rodent eradication yet undertaken.