Palmerston North scientists said stoats or ferrets killed 29 birds found with lethal wounds along the beach Doctors Point near Dunedin this week.
Department of Conservation conservation services manager in Dunedin David Agnew said autopsies by Wildbase (Institute of Veterinary Animal and Biomedical Sciences, Palmerston North) concluded the penguins were killed by mustelid jaws.
"It shows these mammalian pests are hardwired to kill our wildlife for food or sport," Agnew said.
The killing was also a demonstration of the devastation even a single stoat or ferret can cause to native wildlife, he said.
He predicted the deaths would have a serious impact on the little blue population.
"It's going to take many years for the population to recover from this rampant attack—quite likely from just one stoat or ferret."
"At this time of year penguins are particularly vulnerable as they are raising chicks. We've lost these birds plus any offspring they would have added to the population in years to come."
The Dunedin City Council's dog control team and DOC rangers had installed a motion-sensitive camera in place to try and record the killer, Agnew said.
"DOC staff have also placed traps along the stretch of coastline to protect surviving birds."
Doctors Point was a popular dog-walking beach, he said.
"We ask the community to be particularly careful to protect the remaining birds by keeping their pets under control and reporting any predator sightings."
Agnew said the dead penguins were discovered last Saturday by a member of the public who called the DOC Hotline (0800 362 468).
"More dead birds were found in subsequent visits to the area by DOC rangers and the council's dog control team."