KEY POINTS:
Conservationists will be preparing to battle the voracious Argentine ant, which has invaded one of New Zealand's most treasured sanctuaries.
The ants, among the world's 100 worst invasive species, are estimated to be swarming over about 50ha of Great Barrier Island.
The island will be used for the filming of the British reality television series Castaway, prompting concerns from some islanders about the environmental impact of the show.
But the invasion of Argentine ants could be far more devastating.
They out-compete native ants and other invertebrates for food, and preying on them, their eggs and larvae.
The ants also compete for nectar.
The invaders are considered a threat to the ecosystem and, if left unchecked, it is feared they could displace native species, particularly birds and lizards.
Great Barrier is the only home to the rare and endangered chevron skink and also a habitat of the rare brown teal.
Dr Chris Green, Department of Conservation entomologist, said the invasion was a significant risk to the island.
"As they begin to infest and dominate they will affect everything, removing the food sources of other animals and even invading birds' nests and consuming chicks with their insatiable appetite for protein."
The ants "hitch-hike" easily and in 2000 were found to have invaded Tiritiri Matangi.
Dr Green has been involved in a six-year programme to eliminate them from that island and will find out later this year if it has proven successful.
Now the department and the Auckland Regional Council are working on a plan to control their spread - and eventually eradicate them - from Great Barrier.
Des Casey, programme manager for the council, said there were four main areas of infestation covering land owned by 200 people.
"There are properties where you cannot stand on the lawns because the ants swarm up your legs.
"They are very aggressive, will bite if you put a hand near the nest and will destroy everything else in the vicinity."
The first part of a "containment programme", starting next month, involves volunteers walking through an infested area, about 2m, and grid baiting. About 50 volunteers will be needed.
Mr Casey said it was intensive work, but it was hoped it would wipe out about 95 per cent of the ants and give an idea as to how realistic it would be to eradicate them.
"We will hopefully be able to pinpoint where they survive and target those areas for a second programme later in the summer."
Argentine Ant
* Listed by the World Conservation Union as one of the world's 100 worst invasive species
* First found in Auckland in 1990
* Spread naturally, but also great hitchhikers
* Very aggressive: they out-compete native ants and other insects for food
* Threat to flora and fauna
* Creators of the earth's biggest "super organism" - a 5760km network through Italy, France and Spain
