Four wild takahē deaths have been linked to a stoat seen on trail cameras in Greenstone Valley near Queenstown, the Department of Conservation (Doc) says.
Doc warned more of the endangered birds could be killed if the predator remained on the loose.
However, the department said it had stepped up monitoring and trapping at the wild takahē site after the deaths.
Ngāi Tahu and Doc first released takahē on Ngāi Tahu tribal property Greenstone Station about 18 months ago to establish a new wild population.
Doc takahē recovery operations manager Deidre Vercoe said in a statement the predation was not unexpected but the apparent cluster of deaths over a five-week period was being taken very seriously as it showed even one stoat could do a lot of damage.
"DNA analysis and necropsy results point to a stoat, and we have since spotted a likely culprit multiple times on a camera in the area," she said.
"A fifth takahē with an unknown cause of death could also have been a victim.
"Stoats can be extremely trap shy and take some time to catch, so more takahē deaths could become a reality."
Takahē monitoring had been increased, extra traps had been installed, a stoat detection dog was on site, baited trail cameras were in use and the existing trapping network was being rebaited more often.
"Until New Zealand is predator free, any new wild site for takahē will have a level of predation threat.
"This is the reality our native birds face daily on the mainland," she said.
"Current predator control tools make a big difference to species’ survival, but this scenario highlights the challenges.
"Thankfully, the overall takahē population is increasing, so, with the support of our Treaty partner, we can continue to take bold steps to learn more about new wild sites that could support takahē to thrive."
A population of 20-30 takahē had been living in the Greenstone for more than 18 months and the health and productivity of the birds had exceeded expectations, with two active breeding seasons indicating the Greenstone Valley was a promising wild site, the statement said.
The total number of takahē nationwide is more than 500 and more homes are needed for the growing population.
More than half live at wild sites where stoats are present. — APL
