Fiordland Bat Diaries: The Ettrick Burn Part 1

Native bats are something few New Zealander’s know exist, let alone have ever seen. With two species living in Fiordland local rangers undertake monitoring in order to protect and learn more about these special little critters. We join the team heading into the remote Murchison Mountains hunting down short tailed bats.  

It turns out that the Murchison Mountains have more hidden gems than just takahē, with an acoustic recorder picking up the sound of a southern short tailed bat (STB for short) in 2018 in the Ettrick Burn Valley. These devices are designed to be placed in the field and can “listen” for the echolocation of both long and short tailed bats as well as recording all manner of bird calls, wind, rain and river noise. Short tailed bats are notoriously hard to detect as they only emerge after dark and these recorders are the easiest way to get an idea about where they live.

Excitement reigned after the initial discovery but the questions came thick and fast — how many bats were in the valley? Was the population doing okay? Did they come from the neighbouring population 40km away? These detections made the Ettrick Burn bats only the third southern STB population known to still exist. So in the summer of 2019 with the help of some sponsorship from the “Breaksea Girl” charter boat in Fiordland, a 3 person team headed in to catch these bats and try to track down some more.

But how do you monitor an animal that is nocturnal, lives in holes up trees, weighs less than a mouse and can number in the thousands in one colony? With a truck load of equipment! Equipment to climb trees, special bat traps, infra-red video cameras and batteries, data loggers and more batteries, tents, a generator to charge the batteries, countless pieces of safety equipment, food for a week, the list goes on. So much we overflowed the helicopter.

The first task was setting up camp, we were based out of a small two bunk hut the “Log Cabin”, named after the original built by Dr Orbell in the early 1950’s but a log cabin no longer. It’s pretty small to say the least and so we were all sleeping in tents but it provided a space to cook and stay dry. With camp set up we turned to finding net sites and preparing for the night. Reflectors were stuck to markers to guide us home in the dark and likely catch sites were identified.

Trying to catch the first bats was a bit like looking for a needle in a haystack. We knew they should be roosting somewhere in the valley but had no idea where, with our net covering all of 10m long by 2m high. As bat’s echolocation picks up shapes in the dark we use a special bat mist-net to try and fool them. It’s made of thin threads of silk woven together to form a diamond pattern of air and feels like a spider web, it certainly sticks to you like one.

By 10pm it was finally getting dark enough for the bats to emerge and so we started squeaking on bird callers which attract them. At 10.05pm the first Ettrick Burn short-tailed bat flew into our net, the first of this new population.

Stay tuned to the Conservation blog to follow the team to see how they get on in the next post.