Breakthrough in bat recovery project at Pelorus Bridge

Wednesday, 23 March 2016

After hundreds of volunteer hours trapping and countless nights spent at the Pelorus Bridge, the capture of two critically endangered long-tailed bats is a breakthrough for those who have been working to protect them from extinction.

The excitement was palpable as those involved with the Te Hoiere Bat Recovery Project gathered at in the carpark of the Pelorus Bridge Scenic Reserve, between Nelson and Marlborough on Tuesday to glimpse the small bats, some seeing them up close for the first time. 

Conservation efforts to protect the the critically endangered New Zealand long-tailed bat have been carried out by hardworking volunteers for the last five years, but little has been known about their population at Pelorus as they have evaded capture. 

Studies in Fiordland, Geraldine and Maruia have shown that the species were declining at a rate of around 5 per cent each year which could lead to extinction within 50 years.

Bat surveys officer Dr Brian Lloyd said two bats, an adult male and female, were caught on the third evening he had spent surveying the area this summer as part of the Forest and Bird bat recovery project.

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The small and fluffy flying insectivores were photographed, weighed and banded before being released.

'Over the last few years I have been surveying all around the top of the South Island to find out where the bats are,' Lloyd said.  'Pelorus Bridge and across to the Rai Valley seems to be a major centre for bats in this area.'

Lloyd spent last summer surveying the population of long-tailed bats on D'Urville Island and discovered that they were living in pine tree plantations and using forestry roads to catch insects while in flight.

'The forestry is ideal for the bats because you have tracks through big forests and the bats zoom along the tracks and that is a spot where I can actually catch them,' he said. 

Curious as to whether the bats in Pelorus were doing the same thing, he put bat detectors in forestry blocks in the Tinline Valley, near Pelorus Bridge, and discovered they were living there as he thought. 

Bats use high frequency calls known as echolocation to navigate and identify their surroundings and bat detectors are used to pick up these calls and monitor their movements. 

Lloyd said they had no reason to suspect population decline was any different at the Pelorus Bridge but said further research would show if the population was increasing or decreasing.

'At the moment, we have absolutely no idea if whether we had half a dozen bats just going around and around or whether we have got hundreds,' he said.

Last October, more than $113,000 was granted to the bat recovery project at Pelorus Bridge from the Department of Conservation's community conservation partnership fund in an effort to learn more about bats in the region.

Lloyd said now they knew it was possible to catch bats at Pelorus, the next stage was to apply for funding to radio-tag the bats in order to find out more about where they were roosting in order to target protection around their nesting areas, study them and work out the population size. 

The bat recovery project began in 2011 and Forest and Bird volunteer Julie McLintock said in the first year, they spent 20 nights during summer trying to catch some of the bats to tag and release them so they could learn more about the population but were unsuccessful. 

'We watched six of them, flying around this mist net and none of them getting caught and that was the biggest disappointment of all,' she said.

Having spent so many hours listening to the bats at Pelorus and setting nets up in the hope of capturing them she was thrilled with the recent success. 

An extensive trapping program led and maintained by volunteers over a 200 hectare block had made a huge difference in the last five years, knocking back the numbers of possums, rats and stoats.

Volunteer trapping coordinator Jenny Easton said there were eight trap lines in the area with 30 to 40 traps on each, checked by a team of volunteers every week. She had worked to extend the trap lines as more volunteers came on board with the project.

Nelson Management Ltd supported the Forest and Bird project by providing access to their forests for survey work and chief operations officer David Robinson said they were delighted by the news that long-tailed bats had been found in the forest near Pelorus Bridge.

'We know from our colleagues in the central North Island that bats feed and roost within pine plantations,' he said.

'It's been reasonably well-known that there is a bat population around the Pelorus Bridge area, but these findings are exciting for all the people who have been working on this project.'

He said the company were committed to supporting the conservation of endangered flora and fauna and hoped the results of Forest and Bird's work could be incorporated into management initiatives for endangered species.

The Pelorus Bat Recovery Project are in need of volunteers to check the trap lines, anyone interested can contact Jenny Easton at jennym.easton@gmail.com

New Zealand long-tailed bat facts

- Long-tailed bats are chestnut brown, with small ears and a long pointed tail membrane. They weigh 8 to 12 grams, are up to 60 millimetres in length and have a wingspan of up to 300 millimetres.

- The long-tailed bat population at the Pelorus Bridge scenic reserve is the largest in the Nelson Marlborough region.

- Long-tailed bats are forest dwelling and during daytime they shelter in the cavities of large old trees

- Travelling at up to 60 km an hour, they can cover a range of as much as 100 square kilometres.

-  Flying over forest edges, lakes and slow moving rivers, they catch insects using their extended tail membrane to scoop up their prey. 

- Females only give birth to one pup a year.

- Long-tailed bats usually live for more than 20 years.

Source: Forest & Bird