The Department of Conservation had planned to air-drop millions of rat bait pellets to kill the tens of thousands of Polynesian rats on the 2,817-hectare (6,958-acres) Little Barrier Island, the New Zealand Herald reported.

It wants to kill off the rats, called kiore, because they are threatening ancient tuatara lizards, giant weta insects and petrels on the island, an important wildlife reserve in Auckland's Hauraki Gulf.

But a nearby tribe called Ngatiwai has fought the plan claiming that kiore is a treasure, or a taonga.

The 1840 Treaty of Waitangi, under which Maori ceded sovereignty over New Zealand to Britain, includes an explicit guarantee that Maori can keep their taonga.

Maori believe kiore (rattus exulans) arrived in New Zealand with the first Polynesian voyagers more than 2,000 years ago. They were an important food source before Europeans arrived in the late 18th century.

Kiore are largely extinct on the mainland having lost the battle for survival to the European-introduced larger black rat (R. rattus), and brown or ship rat (R. norvegicus).

The Auckland Regional Council, a legal watchdog body, has accepted the Ngatiwai argument and has told Department of Conservation (DOC) to find a new island home for the kiore.

DOC official Warwick Murray said it was proving difficult to find an island for the rats, which could not be moved onto conservation land.

"It's a bit difficult unless a private landowner would be prepared to take them," he said.

Ngatiwai spokesman Terry Mita told the Herald the tribe accepted the transfer of the rats, but only if everyone agreed on how it should be done.

"We would be happy with that as long as how the transfer takes place is talked about between both parties," he said.

SPACE.WIRE