New stoat bait shows promise for protecting kiwi and native wildlife, DoC says

A stoat pictured on monitoring cameras in Borland Valley, Fiordland National Park. Photo / Department of Conservation

The Department of Conservation says a new sausage bait targeting stoats is shaping up to be a valuable tool for protecting kiwi and other native wildlife, after impressive results in field trials.

DoC has been working with pest-control developer Connovation to develop and register a ready-made bait containing the toxin PAPP (para-aminopropiophenone), to which stoats are especially susceptible.

Stoats are relentless killers of native birds, bats and other wildlife, and the key cause of kiwi population decline on the mainland.

They are on the target list for removal in New Zealand’s Predator Free 2050 programme.

For over nine years, DoC principal science adviser Elaine Murphy has led the PAPP sausage bait development.

She said the recent field trials were very successful.

“Over the past three years, we’ve carried out two hand-laid trials and two aerial trials using PAPP sausage baits in the Borland Valley in Fiordland National Park, which regularly has high stoat numbers but few rats – all the trials were very successful."

Murphy said stoat detection was reduced by more than 95% in the treatment areas following the hand-laid bait application, and no stoats were detected in the treatment areas after the two aerial trials.

“This is an amazing result considering we only used one bait per 4-8ha in the hand-laid trials and one bait per hectare in the aerial trials.”

The first two trials involved hand-laying baits over about 1000ha in the forest.

A prefeed of non-toxic baits to prime the stoats was followed by two rounds of PAPP bait, a week apart.

The later aerial trials covered 2000-4800ha with one non-toxic prefeed and a single application of PAPP bait.

Stoats were monitored before and after the operations and in non-treatment areas using trail cameras and tracking tunnels.

DoC said current stoat control methods were limited to labour-intensive trapping and aerial 1080 predator control operations that relied on stoats eating poisoned rodents.

Murphy said new tools were needed to target stoats in environments with few rodents, and when they invade pest-free islands.

“It’s taken many years to develop and test this sausage bait, but it’s now showing great promise,” she said.

“New tools like this are key to achieving Predator Free 2050 and supporting native wildlife to thrive.”

A stoat taking non-toxic sausage bait in Borland Valley, Fiordland National Park. Photo / Department of Conservation

DoC will apply to register the PAPP sausage bait for stoats with the Environmental Protection Authority and the Ministry for Primary Industries once research is complete later this year.

An application will also be made for another sausage bait containing small amounts of the toxin 1080 (sodium fluoroacetate), which has been extensively trialled over the past few years, targeting feral cats, mustelids and hedgehogs.

Carnivores such as stoats are particularly sensitive to PAPP. Photo / Department of Conservation

DoC also plans field trials with a higher dosage of PAPP sausage bait for feral cats and ferrets after earlier trials showed promise.

PAPP was registered for use in New Zealand for stoats and feral cats in a paste form in 2011, but its use has been limited because it needs to be inserted into handmade, minced-meat baits, which is impractical.

Carnivores such as stoats are particularly sensitive to PAPP, but most birds and other mammals are less so.

DoC said the potential risk to native birds from PAPP baits was considered very limited due to very low application rates in the environment and general low susceptibility.