They're small, they're cunning and they're killing our native birds.
Stoats were first introduced to New Zealand in the late 19th century to control rabbits and quickly had a devastating effect on bird life.
Photo: 123RF
Now rangers in one of Auckland's regional parks say the pests are getting smart to age-old trapping techniques, so they have had to get creative.
Over the last year Shakespear Regional Park, on the tip of the Whangaparāoa Peninsula, has faced one particularly problematic invasion.
It began with a single female stoat, who through methods unknown, was able to trespass into the sanctuary.
"One of the things is, we can never really tell with any pest incursion where the point of entry is," said senior ranger Matt Maitland.
"But yeah, they find where they want to use the landscape and we just have to pick up on that and go 'right, where do you want to take us? We'll come to you'."
Pest invasions were not new for the park, but the latest one had been a real headache, made worse because the female stoat had given birth.
And as sector ranger Emma Whitton explained, the stoat and her offspring were not falling for the stock standard trapping technique of rabbit meat and fresh eggs.
There had been some interaction with additional tools the rangers had put out, like double set Fenn traps and run-though boxes laced with stoat bedding.
"So we had interest, but the problem is that you get the interest but you don't actually get the animal to go into the kill trap," she said.
"So it's getting that extra step into the actual trap itself which has been the challenge."
Shakespear Regional Park. Photo: PIXABAY
Other methods and tools to catch and kill the stoats had included poison and camera technology.
Despite the highly intelligent nature of the stoat family, there had been some trapping success with five caught so far.
One operation in May was executed with military like precision, supported by a sniffer dog which discovered a den on neighbouring Defence Force land.
A stoat had made its home in a rubbish tip, filled with planks of wood and metal sheets.
"So we were able to exploit that by placing these long wooden traps into the woodpile itself," said Whitton.
After watching her for a couple of weeks, the rangers moved to set up traps at the den entrance, catching her.
Eighteen hours later that same trap, covered in her scent, was redeployed against the stoat's brother, and a week later it was used again to catch another.
Both Maitland and Whitton still believed the original stoat was on the loose, but they were not giving up the fight.
Maitland said the health of bird-life in the park depended on safety, with the park home to bellbird, kākāriki and the North Island tīeke.
"Those tīeke have actually been impacted by the stoat here, we have far fewer of them than we did this time last year and it's quite possible that if we don't sort this out in a hurry we'll see a local extinction."