16 May 2015
Two rare white kiwi chicks are among seven kiwis killed by an "evil" predator at Pukaha Mt Bruce National Wildlife Centre.
The three chicks and four adult birds died since March in the unfenced, 942-hectare reserve north of Masterton in a spike attributed to a "rogue ferret causing havoc", centre manager Helen Tickner said.
"It's desperately sad but we're an unfenced reserve and sadly, losses like this happen."
While all seven were North Island brown kiwi, two were born with pure white feathers because of a rare, recessive gene passed on by a breeding pair transferred with 28 other kiwi to the centre from Little Barrier Island in 2010.
The two killed, and three others born since 2011, are the only white kiwi known to have hatched in a reserve, although more may exist in the wild.
"Any kiwi loss is terrible but these [white chicks] are special to Pukaha and they didn't last their first month," said Tickner.
It had been a particularly bad year for predation, not just at Pukaha but around the country. Prior to the latest deaths kiwi were sporadically killed at Pukaha, but the most recent was the end of last year. The last similar spike there was in 2010, when nine died in one month, with a ferret again the culprit.
Some ferrets became skilled at avoiding the centre's extensive, Department of Conservation-run trapping network. "They're not stupid... I think the term I'd use is evil," Tickner said.
The trapping programme would be intensified and new trap types, placements, baits and other variations tried, she said. Rats, stoats, ferrets, feral cats and other predators were being caught constantly but the system would never be impregnable. Even expensively-fenced reserves such as Zealandia occasionally suffered predation, she said. "We feel sick about this, but it is a battle, and we feel confident we're doing all we can to try and stop this."
Wildlife veterinarian at Massey University's Wildbase Hospital Brett Gartrell said white kiwi were no more vulnerable than brown to predators, despite their white plumage shining at night, because predators relied mainly on all kiwis' very strong, distinctive smell to pinpoint them before they could see them.
All kiwi were at extreme risk from introduced predators, against which they had not had time to evolve any defence mechanisms, he said. "Young kiwis are dying at an incredible rate... white kiwis are just a colour variation of the regular North Island brown kiwi, and they're important, special birds that need protection."
Individual predators sometimes became "trap-smart" and, when they ranged into a bird-rich area such as Pukaha, big spikes in mortality happened.
