By ANNE BESTON and MEG COLLINS
A tasty new morsel is proving effective in the war on the stoat.
Freeze-dried rats are being used to bait fen traps in the Department of Conservation's mainland island project in the northern part of the Urewera Ranges.
The discovery comes after department staff found a high percentage of digested rat in the stomach of stoats.
Te Urewera Mainland Island project manager Pete Shaw said initial trials using rats as bait failed because they turned mouldy after just a couple of days. He then hit on the idea of freeze-drying them.
Mr Shaw said the rats come back from the factory "dry and crunchy" and last up to six weeks in the trap before going mouldy.
Initial figures in trials over the past six months are impressive. Since February, 57 stoats have been caught over a 1300ha block, 50 of those using freeze-dried rat.
"We reckon we're on to something," he said.
Fen traps are baited with two of the rats and the stoat is killed when it enters the wire tunnel and triggers the trap's jaws by stepping on a treadle.
The stoat is public enemy number one for some of New Zealand's most endangered birds, including kiwi, kokako and the dotterel.
A department technical officer, Andrew Glazer, said the dried rats were also proving effective against feral cats in the Ureweras.
The mainland island in the ranges was established five years ago and covers 50,000ha. It contains some of the most robust populations of native birds in the North Island, including kiwi, kokako, kaka, kereru and bush robin.
Mr Shaw said: "The dawn chorus here now is deafening in spring and summer."
Nationally, up to 95 per cent of kiwi chicks are killed before adulthood, half of them by stoats.
Mr Glazer said the trial would be widened over the next few months to experiment with freeze-dried rats as bait in traps near dotterel breeding grounds.
Stoats succumb to rat attack
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