Fiordland Bat Diaries: The Ettrick Burn Part 2

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 after they have caught their very first short-tailed bat in the remote Murchison Mountains.

Having caught the first Murchison Mountains short-tailed bat the next step is to attach a transmitter to it so that we can radio track it to its roost. Bat transmitters are necessarily small, just 0.6 of a gram so as to not be over burdensome to a 15 gram bat. Larger animal species can have transmitters that last for a year or more, allowing rangers to constantly track the same individuals for long periods of time, but a transmitter that weighs less than a gram has a battery life of only a few weeks. This also means that bat transmitters are attached temporarily with glue rather than a more permanent set up such as a backpack harness on a takahē.

Trialing new techniques on a rare species can lead to great improvements or they can fail terribly. Glue is imperfect and across the country rangers have the same problem of bat transmitters falling off anytime between 3 days and 3 weeks once attached, it’s an unpredictable lottery. The quest for a magic glue that will remain firmly attached for 3 weeks without harming the bats has long been sought-after. Our team has a new type of glue to try, one that has been used on bats in Europe with good reviews. Our first bat has its transmitter attached this way. The following day we radio track it and find the glue has failed, the transmitter lays dropped on the forest floor. Back to the drawing board on the glue front, and back to mist-netting bats for us.

We are in Fiordland, well known for its rain, especially this spring. Rain is a problem for us in many ways, we can not handle bats with wet hands in fear of getting moisture close to their skin and giving them hyperthermia. When it’s pouring with rain they don’t bother flying anyway and then there is the river. It rains for two days. When it stops enough to try catching again the river is still unsafe to cross so we head to our mist net site set up closer to home on our side of the river. Alas we still have wet feet due to the side streams, it is definitely a wet boot trip.

Not all bats are created equal (sorry boys) and by 2am we have only caught two males. The breeding females of both long-tailed and short-tailed bats roost in colonial maternal roosts, allowing for far easier and more reliable monitoring, these are what we are after. Males sometimes visit these roosts but spend most of their time sleeping in solitary roosts rather than leading us to the mother lode. By 2am our feet have turned to ice blocks so we return to camp, have a hot drink and game of cards to wake up before returning to the mist net site. Dawn arrives slowly through the trees, our count remains at two males, it’s time to head home.

By now we can cross the river to the other side and set up a new net site further up valley. And it’s jackpot time with 11 bats caught in little over an hour. We put two transmitters on females (with our old glue). But despite the 11 bats caught it’s a ruru/morepork that steals the show for the evening flying into our mist net in the dark. Ruru are the natural predators of our native bats and are seemingly attracted to their noise. Our squeaking to attract the bats also draws them in and they have been a constant companion at all out net sites. This is the first to fly into our net though and we can’t help but enjoy in the opportunity to see one up close up and marvel at it.

With more rain coming in, it’s time to fly home and have a shower. Our two transmitted bats will have to wait until next time.

Follow the team to see how they get on in the third post and follow the series here.