Pekapeka in the Night: A Bat’s-Eye View on Conservation Efforts.

Tarryn Wyman is a Tonkin + Taylor Ecologist based in our Wellington office and had the pleasure of recently assisting the Department of Conservation with their long-tailed bat monitoring programme.

The programme monitors the population size and survival rate of long-tailed bats in relation to long-term predator control in the Eglinton Valley, Fiordland.

Bats or pekapeka are New Zealand’s only native land mammals. Bats were once common in Aotearoa but have disappeared from many areas due to habitat loss and predation from rats, possums, stoats, and feral cats. Pekapeka roost together and rear their young in hollow trees, where they are especially vulnerable to attack. Long-tailed bats have the highest threat ranking of “Nationally Critical”.

We caught up with Tarryn to get her insights into her volunteering experience with the Department of Conservation and the progress being made with bat conservation.

Tell us a bit about the programme. What is the Department of Conservation trying to achieve?

The goal of the programme is to monitor bat populations in the Eglinton Valley in response to predator control. The aim of the monitoring is to capture bats in traps as they emerge from roosts at nightfall to record their unique band number, or, if they have not been captured before, attach a band. This is called the ‘mark-recapture’ method. Annual survival is estimated from the number of banded individuals detected year by year.

In order to capture bats, we use harp traps; specialist bat traps made of vertical strings, which aren’t detected by a bat’s echolocation. The bat bumps into the strings and gently drops into a catch bag. This is when the band number and other information is recorded, and the bats are released to continue with their night.

How do you locate a roost?

Because long-tailed bats usually change roosts each night, we initially need to capture a lactating female and attach a tiny transmitter. The following morning, she is radio-tracked to determine the location of the maternity roost. The harp trap can then be set up outside the roost entrance to capture the bats as they emerge at dusk. They are assessed for their band numbers, sex, age, weight, and forearm length before being released. The next day, transmitted females are tracked to a new roost; a new trap is set up; and the process repeats.

What methods are being used to control pests that threaten pekapeka? And how are pekepeka faring in response?

Pests have been controlled in the Eglinton Valley in Fiordland since the late 1990s. A mix of traps and poison bait stations help keep pest numbers down. Aerial 1080 drops are also used to combat rat plagues during beech masting – years when the beech trees produce seeds that provide lots of food for rats and mice whose populations then boom.

Predator control is being successful, however. Prior to 2000, the long-tailed bat population at Eglinton was declining by 5 percent every year but that has been reversed and is now growing by 5 percent.

Knowing that you’re contributing and seeing the growth of a native species like pekapeka must feel very rewarding.

It is immensely rewarding, and it was a privilege to take part in this programme, gaining hands-on skills with pekapeka and working in such a breathtaking environment. As Ecologists, we are passionate about protecting our native species and it was incredibly fulfilling to be on the ground contributing to this work looking after our native bats.