Chew cards show decrease in predators in Miramar
May 11, 2019
A chew card study on the Miramar peninsula shows trapping efforts are successfully reducing predators.
The study is part of a Wellington-wide initiative by Predator Free Wellington, a partnership between Greater Wellington Regional and Wellington City Council, the NEXT Foundation, and local iwi. The initiative aims to reduce predators and increase native species on the peninsula.
Miramar was chosen as a testing ground for its isolated location and the barrier of the airport between the peninsula and greater Wellington.
Pieces of corflute, injected with peanut butter and aniseed lure to attract animals, were left out for three nights and collected for analysis on March 22. The chew marks on each card were then analysed to estimate animal populations in the area.
Regional council team leader, Philippa Crisp, said this would be the last chew card study, as the project would move into the eradication phase in July with an onslaught of bait stations intended for the peninsula.
Fewer cards than last year (259 instead of 281) were put out, as Wellington Airport did not agree to take part. Crisp said it likely wouldn’t have changed the results anyway, as in the past no chews were recorded on the runway.
Ninety-five percent of cards were recovered this year, with 13 cards not returned or mislabelled.
A report said that “trapping groups have been effective in lowering rat numbers, especially in the suburbs”. Rat presence had reduced in Miramar’s urban area since last year (18 cards down to four), but rat-chews in the native bush areas went up, increasing from nine cards in 2018 to 12. this year.
According to the report, rat chews had decreased by six per cent, appearing on 29 out of 281 (12%), down from 17% last year. The highest proportion of rat-chewed cards were found on the coast where around 45% of the cards had rat chews.
Image supplied by Greater Wellington Regional CouncilMice left the greatest number of chews, found on 87 of the 259 cards (36%), and hedgehog chews were consistent with previous years, found on 30% of cards.
Only one mustelid (stoat or weasel) chew was recorded, down from six cards in 2017 and two in 2018.
Predator Free Miramar front man, Dan Henry, was cautious of celebrating too soon, as “the greatest use of these studies is a snapshot, year on year”, to show a trend in predator populations rather than a definitive count.
Henry’s organisation provided locals with box-and-trap sets to place in their gardens and in native bush areas, with the aim of lowering predator populations.
The weather last summer had been mild and provided abundant food, and he said an increase in rats would not have been surprising. This would explain the increase in rat chews in native bush areas, he said.
According to Henry, locals were already noticing an increase in native birds and birdsong before the chew card survey.
He said the group had recently been inundated with requests from locals for more traps, which was the really exciting part. “The results are awesome, but it won’t stop what we’re doing.”