Predators ranked in ‘fear’ experiment which could help save native birds.

What happens when you lock one of New Zealand's most hated predators up with two other notorious killers?

You get one scared stoat.

Researchers can now show just how afraid the stoat - the killer of thousands of young kiwi each year - is of its larger counterparts in the wilderness, the cat and the ferret.

An experiment by the University of Auckland and Landcare Research used hidden cameras to simulate a forest environment and found that in a hierarchy of fear, cats and ferrets ruled and the meek stoat rated a lowly third.

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What was a fascinating insight into animal behaviour could also prove important in understanding how the predators might be best dealt with in pest control efforts to save our cherished native birds, said the author of the just-published study.

Patrick Garvey, a doctoral candidate at the university's School of Biological Sciences, filmed 16 captive wild stoats over successive nights and recorded how they responded when a ferret or cat was present.

On the first night, the furry subjects were given the large pen to themselves to get used to the surrounds, before either cats or ferrets were introduced to the arena in cages.

The caged feral cat or ferret was placed on one side of the area and an empty cage was set up on the other, with food placed near the caged animal and the empty cage.

Near the caged cat or ferret, stoats showed increased vigilance while feeding, including standing on hind legs, and most left the "risky" area very quickly.

Only when all the food in the safe area had been consumed did they dare venture into the risky area, keeping a wary eye on the caged predator.

As well, the cat watched the stoat continuously within the arena and at one point tried to attack from within its cage.

Mr Garvey said that although there had been similar studies overseas on such predators as wolves, finding that top predators controlled the distribution and numbers of those below it, the effect hadn't been documented in pests here. "When we are getting rid of predators from our forests, we have to think carefully about the consequences of targeting cats or ferrets because that might allow stoats to thrive, which would be very bad news for our native birds and young kiwi in particular."

The best way to manage the three predators, he said, was to target all of them simultaneously.