Introduction

DOC is shocked with the discovery of rats on two Island Nature Reserves near Whangarei.

Date:  12 January 2009

The Department of Conservation (DOC) is shocked with the discovery of rats on two Island Nature Reserves near Whangarei.

A large rat was found in a trap set by DOC staff on Whatapuke Island last week, which is part of the Marotere/Chickens Islands group. Many traps were set on the island after rodent tracks were recorded during a routine monitoring check. The specimen was later identified as a common ship rat (Rattus rattus). 

Rat prints were also found inside rodent tracking tunnels that had been placed on neighbouring Lady Alice Island, indicating that the rat invasion has occurred on at least two islands in the Hen and Chickens group.

DOC’s Programme Manager Biodiversity, Keith Hawkins, said, “The new discovery is viewed as a serious threat to existing species and to the ecology of the islands.” It is the first time ship rats have ever been recorded on these islands, and how the rats come to be present on the island is unknown, and will be near impossible to confirm. “It is most likely the rat(s) swam ashore from a nearby vessel,” Mr. Hawkins said.

The Marotere Islands / Chickens are dominated by sea birds that nest on the ground. Other species present on the islands include bellbird, saddleback, kokako, kaka, parakeet, tuatara, skinks, geckos, snails and other invertebrates as well as threatened plants. The ecological impact on these unique New Zealand species will be extremely destructive if the rats are not eradicated in the shortest possible time.

DOC has set tracking tunnels and traps on the islands to further determine the species present and the extent of rodent distribution. DOC also enlisted the help of a rodent tracking dog, which was taken to Lady Alice Island. The dog indicated sign of rodents at two locations on the island. An incident control plan has also been developed and will be implemented this week. Further work is required and the Department is investigating its options for the removal of the rodents.

Extensive resources were put into the removal of Polynesian rats from the three principal islands from 1994 to 1997. After the operation, ongoing monitoring recorded strong recovery of tuatara and lizards on these islands. A number of lizards and invertebrates species have been returned to these islands as part of a restoration plan.

DOC is asking the public for their support to avoid introducing foreign invaders to these special places. People are urged to stay well clear of offshore islands where landing is not permitted. There is also signage at local boat ramps to indicate the ‘no landing’ policy for the Hen and Chicken Islands. Boat users are urged to be diligent in ensuring their boats are clean and checked regularly for stow-aways on board their vessels such as rodents and insects.    

The three islands where the work has taken place are part of the Hen and Chicken Islands Nature Reserve. Nature Reserves are set aside under Section 20 of the Reserves Act 1977 for the better protection and preservation of the flora and fauna in its natural state. Public landing on nature reserves is strictly by permit only.

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