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A Norway rat discovered in a trap on the 'pest-free' island of Motuora in the Hauraki Gulf has sparked a Department of Conservation response operation.

Date:  04 February 2010

A large Norway rat discovered in a permanent trap on the ‘pest-free’ island of Motuora in the Hauraki Gulf has sparked a Department of Conservation (DOC) response operation. Motuora, which is jointly managed by DOC and the Motuora Restoration Society and is home to young kiwi chicks and other threatened species, has never had a population of mammalian predators such as rats, stoats or ferrets.

The rat was found yesterday during a regular check, caught in one of the sentry stations designed to detect and trap any invading pests. Based on the level of decay, it is estimated the animal had been dead at least a fortnight. A similar invasion in February 2008 ended with a single rat being caught after several weeks of effort.

The main concern now is the risk that other rodents may be present, prompting DOC staff and volunteers to widen the trapping programme with a large number of extra traps placed over the island. This afternoon a rodent detection dog will be deployed, a tool that has proved effective in the past.

Rory Renwick, Biodiversity Programme Manager for DOC, said the implications of a rat on the island are huge and it was important to ensure no other rodents are present as soon as possible to avoid further risk to the island.

“We’re planning for the worst case scenario, where this may not be the only rat that’s stepped ashore. Staff and volunteers are flat out laying extra traps– we are doing everything feasible to catch anything else that’s there,” he said.

Mr Renwick said it was most likely the rodent had arrived on the island as a stowaway in a visitor’s boat, kayak or gear.

“Motuora is out of the range that rats have been known to swim, so the only other way it could have got here is via people. Even though it was probably inadvertent, it is disappointing that someone’s lack of understanding of the risks has resulted in us having a rat here.

“We are always reminding people to check their gear and boats for pests before landing on, or near, conservation islands and this incident shows why.”

Mr Renwick said Motuora was just one of a number of pest-free islands in the Hauraki Gulf Marine Park that had been undergoing extensive restoration work.

“A rat can have such a huge impact on all the conservation work taking place on these islands. Quite simply, this is preventable. We all have a responsibility to protect these special places,” he said.

Background information

  • Motuora is an 80 hectare island, five kilometres east of Mahurangi Heads, north of Auckland. It is jointly managed by the Department of Conservation and the Motuora Restoration Trust.
  • The island pays a key part in Operation Nest Egg, a programme supported by the Bank of New Zealand Save the Kiwi Trust. North Island brown kiwi chicks are sent to Motuora when they hatch, and live there until they are big enough to withstand stoat predation.
  • There are currently an estimated 60 kiwis on the island.
  • Motuora is being restored with plantings of native trees and the introduction of threatened native species, such as diving petrels, shore skinks and Duvaucel’s geckos. 


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