Search Results For Fiordland Bat Diaries

With two species of native bat living in Fiordland local rangers undertake monitoring in order to protect and learn more about these special little critters. They are on the hunt for a new short-tailed bat colony in the remote Murchison Mountains. In part three we join the team on their second trip after having been rained out.

To say it rained would be a bit of an understatement. Lakes Te Anau and Manapouri are drowning picnic tables by the dozen and the South Island has been cut in half by flooding. We are delayed returning by a week, but with the promise of some fine days it is time to head back in. One benefit of steep sided rivers is that while the Ettrick Burn rapidly turns into a torrent it also quickly drains and by evening we can safely cross the river joined together.

River Crossing.
📷: Warren Simpson

Radio tracking from the helicopter on the way in proved unsuccessful in locating our transmitted bats but on our way to another evening of mist-netting we pick up the signal from one, TX10, and find our first known roost tree. It’s too dark to do any more at this tree but this evening’s mist netting turns up exactly what we are after, an obviously pregnant female who gets a transmitter too, TX30.

Transmitted short-tail bat ready to go.
📷: Warren Simpson

Now that we have found a roost tree it’s time to lug our tree climbing and recording equipment up valley, that’s three 20kg packs back through the river, over the windfall and an hour and half up the track. Of course when we get to the roost tree TX10 is no longer there. We follow the signal back across the river and up the hill to her new roost tree, but it sounds like she is somewhere at the top and our bat sense tells us she is probably solitary – not worth the effort of climbing. Time to dump the gear back on the track and head home for another day. Our spirits are lifted watching a family of whio/blue duck on a rafting trip down stream, five juveniles escorted safely through the rapids by mum and dad. Masters of the eddy they make kayakers look like amateurs.

Whio Family.
📷: Warren Simpson

A new day, a new bat. TX30’s signal is located in a tree up valley, now we are onto something. We climb trees on static ropes, these go from the end we climb on up and over a sturdy fork or limb before heading down to the ground on the other side where they are tied off on another tree. How does the rope get there you say? With a slingshot and fishing line! We fire a sinker up and over the desired fork, fishing line trailing behind. As the fishing line isn’t strong enough to pull the rope we use cord as the middle man, it’s an endless series of winding and unwinding. Safety checks all done it’s time for one of the team to head up and try and find the roost hole.

Setting up for tree climbing – pinging a tree.
📷: Dave Hansford

There’s a split in the tree half a metre long and no more than 5cm wide, I can smell the musky sweet odour which is distinctly short tailed bat, and it squeaks. These are the signs of a communal roost, this is what we have been looking for. Quietly as possible so as to not disturb them we set up a video camera and data logger, their cables run down the trunk of the tree so we can get the data and change batteries without having to climb the tree all the time. Technology is an amazing thing – once it took car batteries to power this gear, now we use lithium ion.

Setting up the video camera.
📷: Warren Simpson

With rain on the way, another transmitter on for safe keeping and the roost camera remaining to do the important work it’s home time again. The first night’s footage of the communal roost shows 207 bats emerging for a night of foraging. This gives us our first minimum number of short tailed bats in the valley. It’s too early to tell how many more might be around, we don’t even know if we have found the main roost tree yet but it’s a start.

Bat antics at the Ettrick Burn communal roost.
📷: DOC

Follow the team in part four to see how the bat count goes.

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.

Removing a short-tailed bat form a mist net.
📷: Warren Simpson

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.

Sometimes you can cross a river.
📷: Warren Simpson

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.

Sometimes you can’t.
📷: Warren Simpson

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.

Walking home at dawn.
📷: Warren Simpson

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.

Catch of the day – the ruru.
📷: Linda Kilduff

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.

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.

The Murchison Mountains.
📷: DOC

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.

Time to set up – the first load of equipment.
📷: Warren Simpson DOC

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.

Preparing the way home.
📷: Warren Simpson DOC

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.

Setting up a bat mist-net.
📷: Warren Simpson DOC

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.

Success! A short-tailed bat in the net.
📷: Warren Simpson DOC

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