Rat bait drop over islands hits late snag

An operation to remove rats from islands in a popular tourist destination hit a last-minute snag when a family refused to have rat poison dropped over their home.

Ninety islands and rocky outcrops in the Eastern Bay of Islands, between Russell and Cape Brett, needed to be sprinkled with bait before another large operation - to clear rats from Rangitoto and Motutapu Islands in the Hauraki Gulf - could begin using the same helicopter contractors.

Both projects have been several years in the planning and the Bay of Islands project initially had the support of all 20 people and families who own or live on the islands.

But on May 28, just days before the aerial bait drop was due to begin, Urupukapuka islander Brian Baker told the Department of Conservation he and his family did not want the poison brodifiacoum near their house.

Mr Baker initially gave his consent to the operation but became concerned about the risk to native birds after speaking to his family.

Use of brodifiacoum, a blood-thinner, has been controversial in other parts of New Zealand because of what opponents say are the unacceptable risks to people and wildlife.

DoC says controlled use of brodifiacoum is safe and any drop in bird populations is more than recovered once rats are removed.

Similar operations have been used to create bird sanctuaries such as the popular Tiritiri Matangi Island near Auckland.

DoC spokesman Adrian Walker said that after one brodifiacoum drop by the Auckland Regional Council, in Tawharanui Regional Park, about half of native dotterels appeared to disappear after getting secondary poisoning from eating sandhoppers.

To avoid a repeat of that volunteers in the Bay of Islands have been picking up seaweed to reduce sandhoppers and clearing baits from areas inhabited by dotterels.

DoC staff will do the same on Rangitoto and Motutapu when aerial drops begin there in the next few weeks.

The Bay of Islands operation went ahead on Tuesday after Mr Baker gave permission to lay rat traps in his house.

Mr Walker said there was a risk of a rat surviving in the area near the family's Otehei Bay home but he was confident the risk was manageable.

Fleur Corbett, chairwoman of a local group formed to lobby for rat eradication - the Guardians of the Bay of Islands - said the vast majority of the community was behind the project. Rats had been a problem on the islands for years.

Dropping bait was "not ideal" but the group decided it was worth it after looking at the environmental benefits.

Mr Baker's daughter Marsha Davis, whose family protested against the bait drop by erecting white crosses in Russell listing native species they said would be affected, said the protest was about getting DoC to control rats in other ways, such as trapping and hunting.

Mr Walker said trapping was impractical because of the islands' steep terrain.

Rats would simply reinvade areas that had been cleared unless they were all eradicated at once, he said.