Concern for bats halts poison plans

A Department of Conservation poisoning operation to control pests, due to take place in the Nelson Lakes National Park, is being halted in response to concern by a Nelson scientist that the rat poison diphacinone could also kill rare short-tailed bats that might inhabit the area.

Brian Lloyd, Bat Surveys field officer contracted to Forest and Bird, said New Zealand's only native land mammal, the bat, was at risk from poisons used to control pest species.

He is to head an extensive survey of bats in the Top of the South this summer thanks to a $54,984 grant from the Lottery Environment and Heritage Fund.

Of two bat species found in New Zealand, the long and short-tailed bat, he said it was the more vulnerable short-tailed bat that could eat the poison bait, given that these bats eat a wide range of invertebrates, browse in leaf litter and have been found dead from poison baits before.

Following advice from Dr Lloyd, Forest and Bird representative Debs Martin has been working closely with DOC to find the best way to reduce rat populations, which are a threat to both birds and bats.

She said while Forest and Bird "supports the responsible and appropriate use of toxins to deal with animal pests" in this case the organisation would assist a DOC survey to establish if short-tailed bats were present in the area first.

DOC Nelson Lakes Area manager Alison Rothschild confirmed that DOC had reconsidered the use of diphacinone in the area after talks with Forest and Bird and would be carrying out a short-tailed bat survey in November, the time when any bats present would come out of hibernation.

"We want to do the best for native wildlife," she said.

Ms Rothschild believed the chance of finding short-tailed bats was low because of their rarity.

DOC would consider using diphacinone next spring instead, with specially modified bait stations, she said.

Dr Lloyd, who worked for DOC for more than 20 years before becoming an independent consultant 18 months ago, said DOC needed to be "very careful" where poison baits were used.

He cited a case where more than 100 short-tail bats were killed at just one roost from diphacinone poisoning, adding that cyanide and 1080 could also kill short-tailed bats. He said the last short-tailed bat found in the Leslie River catchment in the Kahurangi National Park was found dead on a cyanide bait.

"Short-tail bats are seen internationally as a very important species because of their uniqueness 60 million years separates them in evolutionary terms from other bats.

"If they became extinct there would be a global uproar," he said.

Dr Lloyd said despite bats being the country's only native mammal, very little research had been done on these elusive nocturnal animals.

Dr Lloyd led an introductory survey last summer, which pinpointed some areas that long-tailed bats inhabit, including the Aorere Valley, Golden Bay, the Pelorus catchment, the Skeet (a tributary of the Motueka River) and the St Arnaud area.

New state-of-the-art bat detectors, which pick up bats' high frequency echo location calls, will provide further information on their habitats.

The new Lottery funded study will focus on the Pelorus catchment, where trained volunteers will catch and attach radio tags to bats to locate the bats' roosting areas, in an attempt to assess bat populations.

- © Fairfax NZ News