A single ferret has ravaged a breeding colony of protected sea birds in the Catlins, just south of Dunedin.
The predator slaughtered 16 out of the 21 tītī chicks at the Irahuka/Long Point colony.
Forest and Bird has been monitoring the breeding colony since early December when the adults laid the eggs.
They had been progressing well, until Otago Projects Manager Francesca Cunninghame went to do a routine check.
"To find a few chicks lying on the surface dead with bite marks around their necks was very grim.
"It was upsetting because the birds were all in really good condition and only a few weeks from fledging," Cunninghame says.
"To us, it's a stark reminder of the reality of the kind of challenges that we face here in conservation in New Zealand and the sort of impact that these introduced mammals can have."
Tītī, also know as the sooty shearwater or muttonbird, are in decline.
Forest and Bird says the discovery has been heart breaking.
"This is a project that we've invested in, but also you know, has all the heart and soul and blood and sweat and tears of our volunteers and what we've been doing is for six months, we've been carefully babysitting and helping these chicks get to a point where they very nearly fledged and to have one single ferret on one day come through and wipe out essentially three quarters of those chicks is pretty gut wrenching for the team," Chief Executive Nicola Toki says.
While volunteer-maintained traps hold the line against predators, Toki says they won't win the fight.
"Trapping is a fantastic tool, but the problem with trapping is that it's passive, it relies on the animal going into that trap, so you're only catching the animals who are willing to do so which means for the trap shy individuals or the sneaky ones, the ones who aren't encountering traps, we need much more investment in a much greater suite of tools in the tool box.
"You've seen the serial killer that was the ferret this week and so we need to understand how they operate and why and therefore target our resources accordingly and if we do that and we're strategic about it, we're confident that we can make more of a difference than some volunteers holding the line as best they can."
Predator Free 2050
Forest and Bird say it's a supporter of Predator Free 2050, but if it's to be achieved, significantly more resources need to be invested in it.
"We need to invest strategically, and we need it to hurry up, we're out there doing our very best in some pretty tough conditions and the team down south are testament to that but we need to see faster, bigger, stronger, now," Toki says.
"It might surprise New Zealanders to understand that currently we only have sustained pest control over 10%, or thereabouts, of our public conservation lands on any year in New Zealand and so you know if we want to be 10% predator free by 2050 then we should say so, but if we want to achieve that ambitious goal, then we should pull out all the stops, we do the same for things like the America's Cup, there's no reason why we can't do it for this."
The Department of Conservation's Director of Predator Free 2050 Brent Beaven acknowledges predator behaviour, and how predators respond to traps is a challenging area.
He says there's already some investment going into new technologies.
"That includes better lures, new lures that will attract these animals in, different multi species traps, multi kill traps that'll reset and reset and reset so you don't have to be there so often.
"Across New Zealand, there's about $300m a year invested into Predator Free 2050, if we can harness that and focus that on the right areas, then I think we're on a really good step forward."
In the science space alone, there's over $50m a year going into animal behaviour.
"Looking at the behaviour of survivors so the ones that always get away or avoiding traps, how do we get those, what's different about them how do we make that effective," Beaven says.
"Another interesting space is genomic mapping - we map the genomes of most of these predators now and that often opens up new opportunities, you know everything's encoded by genetics or even behaviour so understanding why do animals react certain ways is often encoded in their genes so by understanding that we open up a whole lot of new possibilities around control."
A call for more action, to rid our islands of predators, in the next 30 years.