Forty percent of kea in South Island study killed by predators

Wednesday, 30 June 2021

DOC is conducting a study to find out why kea are dying faster on the South Island’s east coast than the west.

Stoats and feral cats are destroying Canterbury’s kea population, with 40 per cent of a monitored population butchered by predators last year.

Department of Conservation (DOC) staff are now two years into a five-year study – aimed at shedding light on why kea populations are declining faster on the eastern side of the Southern Alps than on the west, to improve predator management.

Kea, a taonga species for Ngāi Tahu, are found throughout South Island mountains and forests and are in decline where threats from predators are not managed.

They are considered nationally endangered, and DOC estimates between 3000 and 7000 birds remain.

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Researchers have monitored 45 kea between Arthur’s Pass and Lewis Pass east of the main divide since 2019 as part of the study. The birds are tracked by radio transmitters and any that died were retrieved to determine the cause.

A flock of kea spotted by DOC ranger Ian Cox in the Kahurangi National Park. (Video first published in February 2018)

DOC science advisor Josh Kemp said results from the first two years showed a sharp increase in monitored kea being preyed upon in the years after the massive beech mast (seeding) in 2019.

“Just six per cent of the monitored kea were killed by predators in 2019, but this jumped to 40 per cent in 2020, most of which were eaten by stoats and feral cats.

“This is the first time we’ve recorded such a large proportion of radio tagged adult kea, both males and females, being killed.”

Kemp said kea were strong flyers, but spent most of their time on the ground foraging for food and roosting, which is why they were so vulnerable to predators.

This research was providing valuable evidence about threats to kea east of the main divide, he said, which would inform future predator control strategies.

DOC controls predators over about 40 per cent of kea habitat on public conservation land through its Tiakina Ngā Manu programme.

Analysis of the dead kea showed stoats and feral cats killed 13 birds. Stoats were responsible for about half of those deaths and cats the other half.

DOC is concerned about the number of kea deaths in the study last year.

Kemp said a survival rate of just 60 per cent of adult kea was very unhealthy for the population.

Kea survival estimates for previous studies in western South Island areas were mostly above 90 per cent.

The sharp increase in predation of the study kea coincided with the crash of mouse populations in eastern valleys the year after the beech mast, which may have contributed to stoats taking larger prey, he said.

Most of the kea tracked in the study lived in areas where predators are not currently controlled.

However, Kemp said two birds were killed in the Hawdon Valley in Arthur’s Pass National Park, where predator control targeted rats and stoats to protect critically-endangered orange-fronted parakeet.

There are now plans to start trapping feral cats in this area.

Anecdotal reports showed feral cat numbers had been increasing in the study area over the past five years, Kemp said.

The eastern kea study will continue until 2023.