Report to the Community Board
Pest Liaison Group Meeting: Successful removal of rats off Rakino
by Tony Bouzaid

Environmental News Issue 5

ONCE EACH QUARTER the Auckland Regional Council run this meeting and in June the topics were:

• Waitakere River/Te Henga Wetland Willow Control programme.

• Rakino Island rats, a success story:

• Weed Control in Bush and Natural Areas — A new perspective on Contracting — Te Ngahere in partnership with Auckland City.

Of these the most interesting from a Barrier perspective was the Rakino Island rats. This was an operation carried out by the Auckland Regional Council not Department of Conservation and is particularly interesting being the first rat eradication on an inhabited island.

Most of the 146 hectares is private property with 75 dwellings although there are only 35 permanent residents. The eradication was done using 750 bait stations on a 50m x 50 m grid with three lines along the cliffs. All the offshore rocks and islets were done as well. The stock wasn’t removed instead the bait stations consisting of novaflow drainage pipe was buried in the ground with a clod of kikuyu and soil over the top but with the ends exposed.

Brodificoum bait was used and re-baited every 3 weeks until no more was taken. Once this occurred the drainflow was replaced with tracking tunnels with inkpad cards to indicate the presence of rats. Brodificoum was still used as the bait so that if there was a rat present it would soon succumb. A contractor was hired to set up and bait the stations until there were no apparent rats present and then local volunteers took over monitoring the tracking tunnels.

The only animals that succumbed to the bait other than the rats were turkeys and sparrows. It has now been two years since the last rat on the island but precautions are still taken at the potential points of entry. The ferry wharf, barge ramp and boating visitor bays have bait stations and traps maintained. Both barge and ferry operators maintain bait stations and traps on their vessels and the rat free status of the island is publicised.

Since the eradication there has been no explosion in the mice population which had been expected after their principle competitors had been eliminated.