Rat found on vermin-free Abel Tasman island

A rat has been found on remote Adele Island. Photo / Getty

A rat has been caught in a trap on a New Zealand island declared vermin-free in 2009.

The unwanted rodent found on Adele Island in the Abel Tasman National Park, near Nelson, has sparked intense trapping and monitoring to ensure it was a lone invader.

The male rat was found on Thursday and appeared to have been dead for about two days, Department of Conservation Motueka area manager Martin Rodd said on Friday.

"We don't know when it got onto the island but our monitoring systems showed no sign of rats when checked in mid-December. We also don't know whether it was a single rat or there are others."

More predator traps will be installed, monitoring will be increased and a tracking dog will comb the 87-hectare island for more possible rats.

Mr Rodd said the rat may have come from a boat or swum across from the park mainland, about a kilometre away.

The find was a reminder to people to ensure their boats and kayaks were free of such pests before landing at Adele and other pest-free islands, he said.

Adele, Fisherman and Tonga islands were declared pest-free in 2009 following an extensive pest-trapping program and the Abel Tasman Birdsong Trust started returning native birds to the islands, including the South Island robin.

- AAP