Record Number Of Native Pekapeka Bats Counted At Marlborough's Pelorus Bridge

Thursday, 27 March 2025, 9:16 pm
Article: Maia Hart - Local Democracy Reporter

Record high numbers of long-tailed bats have been captured and tracked during an annual count of the vulnerable mammal in the Pelorus area, Marlborough.

Nick Eade, who helped with Forest & Bird's Te Hoiere Bat Recovery Project, said wile the numbers are encouraging, it's probably too early to draw any conclusions as to why they're increasing.

Eade said it could be down to more intensive predator control, or perhaps they were just getting better at tracking the bats.

After all, the pekapeka tou-roa were not easy to catch, and doing so required working through the night.

Now in its seventh year, a total of 380 bat captures were recorded across two key sites at the Pelorus Bridge Scenic Reserve and Rai Valley, between Blenheim and Nelson, in the 2024-25 summer season.

"The idea is that towards the end of the season, you'd be almost catching what we call recaptures, and very few new bats, and then you know you've got most of them," Eade said.

A team of four, and a few volunteers, worked through the summer months to track the bats.

At Pelorus Bridge, 205 captures were made of 122 individual bats, with 79 newly banded, and 43 recaptured from previous seasons.

This was an increase on last season's 86 individual bats, which could have been down to the discovery of a second group of bats in the area.

In Rai Valley, 175 captures were recorded, with 80 individual bats identified. Of those, 54 were newly banded and 26 recaptured. The number of known bats there nearly doubled from 45 to 80.

"Ideally, you just keep catching and catching until you have no new bats at all," Eade said.

"If you do that every year for a period of time, you can start working out survival rates and whether the population's declining or increasing.

"That is what we would like to do, but it takes a long time to get that baseline data to get enough numbers so that you know you're just re-catching the same bats.

"We're still not at that point, but we're getting close."

Eade thought it was only the third season the bats were being caught in high numbers.

"Certainly, this season we had a good go at it and we got quite good numbers, it was encouraging.

"Once we've caught a few we can put a little radio transmitter on its back, so we glue them on.

"A bat only weighs 9 to 12 grams, so they're only tiny, like a little mouse. So, the transmitters are tiny too."

An aerial was then used to track the bat. The transmitter would also eventually fall off.

"When they go to bed in the morning, we track them at dawn and find out where they've gone, so which tree they've gone into."

This identified "roost" holes, where the bats, mostly females and pups, were found in groups over the summer when they were breeding.

"In the afternoon we'd be setting up a roost trap, and then in the evening we'd come back at dusk when they come out and they fall into our trap, hopefully."

The bats were bagged, so they could be weighed, measured and banded.

"And maybe sticking a radio transmitter on some of them and seeing if they're male and female, and seeing if they're juveniles or adults.

"If you do have a roost, that's a big day, because you do your dawn tracking, you might go back to bed for a few hours, then you do the afternoon set up and then you spend the night out with the roost. You might get to bed at, say, 2am and then someone's got to get up at 5am to go dawn tracking again."

During winter, the bats would hibernate. Eade said they did not know exactly where or how far they went.

"So they are quite vulnerable to predation."

New automatic traps to catch predators helped, she said.

"That's been a real game changer and we're still fundraising to try and get more of those traps at Pelorus."

That long-term predator control would help in the long run.

"If we're pretty sure they're improving and we know the predator control is good, we can be fairly confident that they'll be a self-sustaining population."

Protection of the pekapeka began nearly two decades ago, with bat monitoring added in 2018.

The recovery project secured a boost in 2018 from the Te Hoiere Project, in which the Marlborough District Council was a partner, and the government's Jobs for Nature programme.

LDR is local body journalism co-funded by RNZ and NZ On Air.

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