Pomona Island Charitable Trust - Rodent Eradication

Rodent Eradication

Project Objectives
To remove all rats and mice from Pomona Island.
To remove all mice from Rona Island.

Background
Rats and mice were present on Pomona Island for many years. A total of 312 rats were caught in the stoat traps between August 2006 and July 2007. In addition, live rats were often seen running around the island by volunteers as they checked the stoat traps. Mice were known to eat the meat bait in traps on both Pomona and Rona Islands.

Method Used
Best practice for eradicating rodents from islands is to use an aerial application of brodifacoum - an second generation anti-coagulant poison. A resource consent was needed to carry out such an operation on the islands. An Assessment of Environmental Effects (AEE) was prepared by volunteer Megan Willans. In addition, a Social Impact Assessment, funded by the Lottery Grants Board, was completed in order to gain the views of the local community on the restoration of the islands in general and in particular on the planned use of an aerial poison operation to eradicate the rats and mice. The resource consent application was submitted to Environment Southland in January 2007. Seven submissions were received, five in support and two against. Careful negotiation by Murray Willans (the Trust's DOC advisory Trustee at the time) with the NZ Deerstalkers Association enabled the Trust to avoid a costly hearing process. Consent for the operation was granted in May 2007.

In July and August 2007, two aerial applications of brodifacoum were undertaken on Pomona and Rona Islands. South West Helicopters was contracted to fly the missions, with Chief Pilot, Peter Garden, donating his flying time to the Trust. Nick Torr volunteered his knowledge and expertise as Operations Manager and ground handling was carried out by a number of volunteers with assistance from DOC staff. In total, 7.1 tonnes of bait were dropped on the islands over two separate days (8 July and 18 August 2007).

Current Status
No evidence of rats on either Pomona or Rona Island has been found since the aerial operation, so the islands are rat-free.

A single mouse was found in a trap in a rodent motel on each of Pomona and Rona in June/July 2009. An extensive trap network, targeting mice, has been placed on both islands since then. It is looking increasingly likely that this was a re-invasion probably from a boat or by swimming, rather than evidence of a remnant mouse population on either island. In March 2010, a further single mouse was trapped on Rona.

Thanks to:
An anonymous benefactor for funding the majority of the costs associated with the rodent eradication programme.
Community Trust of Southland for making up the shortfall.