Ferret highway: Transmission Gully creates path for pests to move south

Wellington’s Transmission Gully may have made the commute to the city easier for drivers, but now pests are using the road to run towards vulnerable kiwi populations.

Possums, stoats and ferrets are using the highway to commute from Kapiti Coast into the wider Wellington region and the council is worried it could decimate the newly restored kiwi population.

Ferrets feast on New Zealand’s ground-nesting birds and are capable of killing adult kiwi - unlike stoats which primarily attack chicks.

Jack Mace, director of delivery at Greater Wellington Regional Council, said the ferrets use the road like a corridor.

“If you think for us, the roadways create a much easier path, it’s the same of animals.

The Wainui Saddle area of the Transmission Gully motorway. Photo / Mark Mitchell

“It’s a beautiful big road, easy to follow and provides a straight line into Wellington from up the coast where ferrets are more plentiful and so ferrets will find it much easier to move down.”

Mace said when the Kāpiti Expressway was completed, there was a big jump in the number of ferrets found in traps and they’re seeing a similar increase now, with a ferret being spotted as close as Haywards.

Luckily for the council, this ferret had already become roadkill.

He said ferrets are known to travel 30, 40 or even 50km/h in search of prey and when they find it, they’re quick to wipe it out.

“They’re capable of wiping out large numbers of kiwi in very short timeframes.

And in some cases, 50 per cent of kiwi populations within a matter of weeks, have been killed.”

It’s concerning given that Capital Kiwi has been working to restore the population of the native bird in the hills of Makara, southwest of Wellington.

Ferrets feast on New Zealand’s ground-nesting birds and are capable of killing adult kiwi. Photo / Nick James

The Capital Kiwi Project is one of the first landscape-scale projects funded by Predator Free 2050.

The project received a Department of Conservation permit to allow the relocation of 250 kiwi into the landscape over the next six years, with 50 already in the hills.

Penny Gaylor, the chair of the Greater Wellington Regional Council environment committee said the situation does concern her.

“We’ve had the experience of where, I’m the ward councillor for the Kapiti Coast, where when we put the expressway and there’s been a lot of concern that became a corridor for pests to travel along the coastline and along the expressway corridor.

“It particularly focuses our attention, but we’re certainly realising that we have to focus our attention in lots of different ways to manage all kinds of pests.”

Greater Wellington’s group manager of environment Lian Butcher confirmed there are previously controlled areas that are now under threat - including the Makara kiwi project.

“Possum free Whitireia peninsula; Baring Head and Parangarahu Lakes where dotterel colonies are located; Wairarapa Moana, home to endangered bitter. Kōkako and kiwi at Pukaha Mt Bruce in the Wairarapa are also threatened by predator migration.”

The council is now considering its options to tackle the problem.

“We hope to work with partners including councils, agencies like Waka Kotahi and the community to slow predator migration along these pathways and provide protection on a wider scale.”

Nick James is a Newstalk ZB reporter based in Wellington with a focus on the environment, infrastructure, social and Wellington issues. He joined Newstalk ZB in 2021.

Vita Molyneux is a Wellington-based journalist who covers breaking news and stories from the capital. She has been a journalist since 2018 and joined the Herald in 2021.