Stoat study tracks pest migration

Auckland Council is funding research into stoats to offset a significant threat to Hauraki Gulf islands.

A $30,000 grant made to the University of Auckland helps fund two years’ work by PhD student Andrew Veale to conduct research into stoat migration. His research will be used by the council to help plan eradication and surveillance programmes by identifying where stoats originate from.

Stoats pose a major threat to our native birdlife and are found on more than 90 islands around New Zealand. It is essential that preventative programmes are put in place to protect our treasured pest-free Gulf islands.

Veale, who is based at Landcare Research, says his research focuses on the dispersal and connectivity of stoats, which is very useful in developing management programmes.

“What I’m hoping to do with the Auckland region is to get an idea of the genetic population structure of stoats. For example, are stoats in Hunua connected to stoats in the Waitakeres, and how often do they swim to islands?

“If areas are connected, you need to develop management programmes that cover the areas simultaneously to be effective,” says Veale.

“Stoats have a high mortality rate. Around 80 per cent die in the first year of life so there is a great competition for resources, which leads to increased dispersal. As adept swimmers they set out for islands with the hope of finding lots of food.”

Rangitoto Island is an example of how Veale’s research works. Last year, after an eradication programme had been put in place, a stoat was found in a Department of Conservation trap.

“I studied DNA samples that I collected prior to the eradication campaign and combined them with DNA samples from the mainland. The samples showed the trapped stoat was from the mainland, not an adjacent island,” says Veale.

“This sort of information helps enormously in eradication programmes and tells us how safe a patrolled area is from reinvasion.”

Veale is hopeful his research will be useful in terms of the future eradication of stoats from big islands such as Waiheke. It will enable scientists to sort out what the risks are and where stoats come from so they can allocate resources accordingly.

“Once we get a handle on the full genetic population structure we can create some exciting management programmes that will reduce their numbers.”

Stoats were first introduced into New Zealand by settlers in the 1880s in an attempt to control rabbits and hares and they live in any habitat where they can find food. They live for up to six to eight years and juveniles have been known to travel more than 70km in two weeks.

Auckland Council biosecurity manager Jack Craw says DNA samples not only determine where pests come from, they can also help determine if they made their journey by stowing away on a vessel or by swimming.

“This information is absolutely vital for creating and maintaining pest-free status on our precious Gulf islands.

“The recent stoat capture on Kapiti Island highlights the need for in-depth research to determine pest origin and movement patterns.”

Hauraki Gulf stoat-free islands include:

Great Barrier and associated islands
Little Barrier
Rakino
Mokohinau Group
Rangitoto-Motutapu.