Native species at risk from pest control toxin

Paul Simmons in action on the weekend with a rat trap using non-toxic bait. Photo / Lauren Gruber

A toxin that's widely used by Coromandel pest control volunteers has been shown to kill native fauna including morepork, kiwi and the saddleback found on Red Mercury Island (Whakau).

It's why a toxin-free group in Whangamata is celebrating a small windfall that they see as a big gain in other ways.

Warriors for the Birdsong of the Forest, or Korihi te manu o ngahere toa in te reo Māori, received $3000 funding from Waikato Regional Council which they'll use to lay more hand-built traps.

Numerous other community-led predator control work uses the toxin brodifacoum, that is the subject of a study on secondary poisoning, published in the New Zealand Journal of Ecology. Other groups have shown interest in non-toxic methods.

Paul Simmons says until now the group has relied solely on donations and $100 from each of their volunteers' own pockets to fund wooden traps to catch rats, possums, weasels, stoats, ferrets and feral cats between Whangamata and Whiritoa.

Centred around the property of Rick and Shona Taikato, the grid of traps has already caught 412 pests including more than 100 mice and 200 rats, 60 possums and four cats.

The land is part of the Parakiwai Kaianga Settlement, of which the Taikato family own 37ha and manage the land without the use of chemicals.

"My old man used to look at it as the supermarket. You would jump on the horse and source food from it," Rick told Coastal News. "The medicines that came out of it were gathered by our nanny."

Rick believes certain Māori medicines would be impacted if chemicals were used on the property.

Paul Simmons in action on the weekend with a rat trap using non-toxic bait. Photo / Lauren Gruber

Paul is learning about bird species as he goes and was interested to learn Rick's views about wanting to safeguard plant species for medicinal purposes. An avid researcher and note taker, Paul knows of the damage that pests can do to native wildlife.

"In my research, a rat kills 50 birds in its lifetime and that's a lot, not even counting the eggs they take."

He is determined to show that gains can be made without chemicals. So far the toxin-free group has given 388 volunteer hours, and covered an area of 12.6km.

Some 108 traps were made by Whangamata Menz Shed using materials donated by Bunnings Whangamata and Saltwater Surf, First National, Whangamata Real Estate and the volunteers themselves.

"It's nice to now say 'we've done this' and now we are doing that," says Paul. "We're not just 'gonna do'."

Paul Simmons with some of the traps built by Whangamata Menz Shed for the pest control group using no toxins. Photo / Coastal News

The work is complementary to predator control undertaken by DoC through its Battle for Our Birds campaign but unlike DoC and WRC, does not use 1080 or other poisons like brodificoum.

It is the first time that WRC has given funding to the Warriors for the Birdsong group, which was previously denied on the grounds that they wanted to prioritise areas that contained the critically endangered Australasian bittern, which is thought to live in wetlands.

"We found one in a freshwater pond in this area," explains Paul, who says he was looking for an endangered species so he could access the funding.

An Australasian bittern. Photo / DoC

"Across the road, Dennis [Allison] has three. That gives us four in this small area and there's only thought to be less than 1000."

He says the group wants to hear from people who think they have bittern on their property. After 2.5 months they've also seen "huge" numbers of wood pigeons.

One poison that's used by other predator control groups is brodifacoum, which Paul particularly dislikes because it is not water soluble and indiscriminate.

"That's why some people like using it, anything that comes along eats it and unless they get a lethal dose, they don't die, the consume it and spread it. The problem is rats and possums make crumbs, it doesn't target the species and it lingers in the environment for a long time. I also think it's cruel."

A peaceful protest against 1080 drew about 30 people in Waihi on Saturday. Photo / Supplied

Jo Monks, science adviser for the Department of Conservation, authored a paper on the impact of brodifacoum on non-target wildlife.

The paper reviewed literature of brodifacoum effects, a poison that has been proven to kill native birds and fauna such as native geckos that consume brodifacoum bait.

Though at low risk of toxicosis themselves, reptiles act as vectors of brodifacoum and create a risk of secondary poisoning to native birds, the paper found.

Regional councils use brodifacoum to protect sites identified as Key Native
Ecosystems against possums, as vectors of Tb. Sustained brodifacoum use continues
in some areas to protect threatened native fauna.

Jo says she believed brodifacoum has an important role on offshore islands where total eradication of pests was the goal. But she suggests caution using it in mainland locations because of its long life and persistence in the environment.

"We need to use it carefully and think about using toxins that are most persistent, particularly when it's repeated use.

"My take overall is that there's a range of tools for any pest control group, some are using toxins and some aren't. The mix that any particular programme will use will be specific to the scenario they're dealing with."

What do you think? Email alison.smith@nzme.co.nz.

- Volunteers to help Paul and the group are welcome. If interested please text Paul at 0279752640 or email possumhunter007@gmail.com.