There were once three species of bat in New Zealand: one, the greater short-tailed bat, became extinct in the mid-1960s and there are only two left - the lesser short tailed bat and the long-tailed bat.
Debs Martin has been leading an effort to save the critically endangered long-tailed bat in Pelorus Sounds for nearly a decade now. She’s been the regional manager for Forest & Bird in the top of the South Island since 2004.
The bat is being driven to the brink of extinction, she says.
“The long-tailed variety are the most endangered and it’s mainly because of two things: one is habitat loss with the felling of our large forests particularly through the 1800s and early 1900s and more recently it’s predation from stoats, rats, possums but also cats and wasps; we’re increasingly worried about their impact on bats too.”
Wasps compete for food in the beech forests where these bats often live, she says.
“They need to fatten up during autumn and in autumn, with wasps throughout a lot of our beech forests they will consume all the honey dew, but then they’ll also consume most of the insects that are in the forest as well, so there’s the deprivation of food source.”
She says there is also some evidence that wasps will sting and eat the bats.
“These are small creatures, they live in the trees and they would be very vulnerable to wasps in the way that insects are.
“Wasps consume baby birds in the nest … wasps are voracious feeders throughout our beech forests.”
She says getting on top of predation is the number one priority.
“They’re going into a decline at a rate of potentially 70 percent over the next while.”
But to get a real sense of the bat population in the area, they have to trap the tiny creatures when they’re flying around at dusk.
“We have to catch the bats, put a small radio transmitter on them and using that locate their bat roosts. Once we’ve located where the bat roosts are we can start to do population counts.”
Once the bats are out and about they can range quite freely she says.
“Their ranges can be up to 100 square kilometres, they fly at about 60 kms an hour, they come out at dusk, they’ll often have a drink and a feast on the insects coming out and then they will range around their territory looking food and social opportunities before coming back to bed in the early hours of the morning.”
Trapping them is quite a skill, she says. they use harp traps placed on popular bat “fly ways.” The harp-shaped trap has two wires running down it which the bat flies into and then slides into a net.
New Zealand’s long-tailed bats are tree-dwellers preferring to roost in hollows in beech trees; but have also adapted to some extent.
“What bats are looking for is a place to rest during the day time that is going to be stable … constant in temperature and not get too hot and not get too cold.
“In places like Geraldine bats have been known to tuck into the limestone cliffs and have adapted to trees like willows and poplars, in fact a couple of female roost trees in Geraldine were about to be sold for firewood before they discovered them in these big old poplars.”