North Island long-tailed bat thriving in Taranaki

The North Island long tailed bat. Photo/ Supplied.

What's smaller than a mouse, weighs just 8-10 grams, and flies at 60kmh?

It's the North Island long-tailed bat, a little animal that along with its South Island cousin, is New Zealand's only land mammal.

It's officially classified as "nationally critical", with latest estimates forecasting numbers to be declining at a rate of 90 per cent over the next three generations – and a generation is considered to be 12 years.

This is the highest threat level for native species before extinction in New Zealand, and it puts the miniature bat in the same threat tier as iconic bird species such as the kākapo.

That's the bad news. But the good news is that a new survey in East Taranaki hill country has shown that not only are the long-tailed bats resident in the area, but thanks to extensive predator control their population may be increasing.

What was known as the Purangi Fauna Survey was conducted in early March by Coromandel-based Red Admiral Ecology for the East Taranaki Environment Trust, which administers Experience Purangi, a 13,000ha ecological area east of Inglewood.

A total of 21 automated bat detector units were deployed alongside the Waitara River and connecting gullies between March 3 and 8. They were fixed to shrubs and trees about 1.5 metres above the ground, and set to run from prior to sunset through to just after sunrise each night.

High frequency echo-location pulses emitted by the native bats were detected by the units. The results were encouraging, with bat activity detected by all the stations within 15 minutes of sunset.

"This indicated that this critically endangered species is resident within the Experience Purangi area," says Paddy Stewart of Red Admiral Ecology in his survey report.

"The timing of bat activity soon after sunset indicates that the bats were most likely roosting in the upper reaches of the survey area," he says.

Trust chair Karen Schumacher says the survey results are good news.

"The North Island long-tailed bats have previously been detected at Purangi during field studies by students from Kaimata School and Inglewood High School, and now this latest survey confirms everything," she says.

"Experience Purangi has been undertaking extensive predator control for several years now in a big effort to grow the resident population of North Island western brown kiwi. That is proving highly successful – and it is now obvious that the same predator control operations are also helping grow the resident populations of the little native bat."

The Purangi Fauna Survey also conducted a count of kiwi numbers by setting up 14 observer listening stations, with observers completing up to three, two-hour listening sessions.

There was good news from that survey, too – a total of 24 listening sessions detected the calls of at least 53 male kiwi, well up on the 47 males detected from 42 sessions in 2017. And this was despite the fact that the latest survey was completed six weeks earlier than the 2017 effort, which means it is likely the birds would not have been as vocally active this year as they were three years ago.

"This is continued good news for the project, as adult survivorship has been an issue for other Western kiwi populations," says Paddy Stewart.