Volunteers strengthen Wellington skyline's defence against possums

Wellington’s skyline runs from the highest peaks of Mākara to Mount Kaukau, ending in Johnsonville. These connected landscapes benefit wildlife as they can move across into areas such as Khandallah Park and Ōtari-Wilton’s Bush – but so can pests, like possums.   

Possums consume an exorbitant amount of vegetation, defoliating trees, disrupting flowering and fruiting, while directly preying on eggs and chicks of various native birds. Controlling them in our reserves is the foundation of forest recovery and what has supported the increasing bird numbers in the city over the past few decades. 

Since possums are well managed in the reserves, a focus has been to try and prevent possums from making their way from Mākara and Ōhariu Valley over the skyline to the native forests, using ground-based traps. 

Mike Shaw, a dedicated volunteer who has been trapping on the skyline since 2020, began noticing how the traps were proving less effective on possums and reached out to the Council to improve them. 

“Because the traps were on the ground, anything could get in to eat the bait. Once the bait is removed, there is a huge drop-off in the catch rate since you rely on someone rebaiting the traps to make them effective again.”

As work was ongoing with the Skyline Possum Trapping group, Biosecurity Specialist Pest Animals Debbie Hawker, from the Council’s Urban Ecology team worked closely with volunteers to develop a strategic new solution for the trap network. 

“With kiwi coming into the landscape, this was a great opportunity to upgrade our skyline possum network. We decided to switch to ‘Flipping Timmy Traps,’ which are elevated from the ground reducing the risk to ground nesting birds, and reducing bait taken by non-target species, like rats.”

The team experimented with different bait pastes to see what would entice possums to the traps. When they moved to long-life cinnamon lure paste, the number of catches began to grow, says Mike. 

“We suddenly increased to catching 17 possums in a month! The bait stays fresh for a good month or two, which means we don’t need to clear out the old bait as often."

Mike often spends two-and-a-half hours biking most weekends clearing the traps and checking the bait. When the weather is good, he goes on night-rides where he can catch the reflective eyes of possums and note where they are coming up over the skyline.  

“We’ve been strategic in the last 12 months and monitoring where the possums are showing up. Park Ranger Adam has been helping me adjust the posts and traps on trees to target those areas and even moving them by a few metres can make a big difference.”

The numbers speak for themselves, with trapped possums increasing to an average of 21 per month. More recently, 36 were caught in October and 45 in November, compared to 6 and 8 the year before.

Park Ranger Adam Groenewegen says that this increase is not only down to the new traps and pastes, but the efforts of hard-working volunteers like Mike and other members of the team.

“People like Mike are dedicated to go up regularly and maintain the traps. The one that he looks after on the skyline is the frontline for our reserves. 

“His work safeguards regenerative native forests, including Moko, the 800-year-old rimu in Ōtari, with these traps playing a vital role in protecting our precious places."  

Echoing Adam, Debbie believes that the biggest asset in wild Wellington is the community conservation approach and the sheer volume of hours the community volunteers put into taking care of nature in the city.

“The great thing about changing the traps and doing these improvements is that it benefitted the volunteers who do amazing work – it makes them easier to check, they don’t have to bend down, you can see them from a distance and service them - meaning less frequent checks, more catches, and more fun doing it! 

“If you want to join the effort making Wellington a city where people and nature thrive consider trapping on your land or joining your local community group by getting in touch with our Park Rangers.”

You can check out the stats and figures of the Skyline project through the TrapNZ website. Or you can find out more about how to volunteer outdoors with the Council on our website.

Lead image courtesy of WellingtonNZ.