Saving New Zealand's critically endangered long-tailed bats

Friday, 18 October 2019

They're not much bigger than your thumb and they only come out to forage at night.

'Cryptic' and critically endangered, with the same status as kākapo, the behaviour of New Zealand's long-tailed bat, or pekapeka, makes counting and protecting them a real challenge.

However, their numbers are now in the hundreds rather than thousands.

There are small colonies of usually less than 20 bats around the North Island and in the north and south of the South Island. But along the east coast of the South Island, the only place you will see them is in South Canterbury, particularly Geraldine, where they fly out from their roosts in totara and matai trees in Talbot Forest.

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There are also colonies in Peel Forest, in the gorges of the Orari, Waihi, Te Moana, Kakahu and Opihi rivers, and in limestone areas around Hanging Rock.

The long-tailed and lesser short-tailed bat are New Zealand's only two remaining species of land mammal. A third – the greater short-tailed bat – is presumed extinct, not having been seen since 1967.

The level of public interest in the bats is rising, with efforts under way to protect them from predators and ensure no further loss of their preferred native tree roosts.

The bats only weigh up to 11 grams, can fly at up to 60kmh and emit a low-frequency call some people can hear.

Department of Conservation principal science adviser ecosystems, Colin O'Donnell, told Stuff pekapeka were in 'a lot of strife'.

DOC had earlier monitored the South Canterbury bats for five years and found their numbers were dropping at nine per cent a year, making extinction within a decade a possibility.

'They'd be becoming extinct if we didn't do something about them. That gives us a good incentive.

'We can get local estimates of their numbers but we can't really say how many there are, They are incredibly cryptic, they're about the size of your thumb and fly around in the dark.'

It was not known how long the bats lived, but the oldest one they had monitored was 25.

Tiny radio transmitters attached to healthy bats helped track them back to their roosts.

Pekapeka preferred to roost in old, thick trees that heated up during the day and reached their maximum temperature at night. The young could then stay warm while their mother hunted in the dark, he said.

However, South Canterbury bats were now being found in poplars, willows and cabbage trees, which were poorly insulated, putting the young bats at risk.

DOC's Geraldine biodiversity ranger, Damien Bromwich​, told Stuff the most important recent efforts had been in advocacy, in publicly promoting the bats and in predator control.

In one project, aluminium bands had been put around native trees where bats were roosting. The smoothness of the metal meant possums, cats, ferrets and other mustelids could not get a grip to climb the tree to the roosts.

'It's probably too soon to tell if there is a big change, it's basically a five-year programme of monitoring, which is just starting this year.'

Public interest in the bats was rising, he said.

'We've done a couple of night-time safaris, explaining about the bats. But we could only take 50 when 150-plus wanted to go.'

There were colonies in Talbot Forest, Te Ngawai and at Kakahu-Hanging Rock, and the bats were likely to feature in next month's Geraldine Festival.

O'Donnell was optimistic for the bats' future.

'One [southern Fiordland] colony was down to 24 breeding females, but it's now up to 140-150.

'It shows we can make a difference.'