Search Results For Fiordland Bat Diaries

Local rangers in Fiordland undertake short-tailed bat monitoring in order to protect and learn more about these special, little native critters. But sometimes they are not the only little critter on show…. The New Zealand bat-fly is a wingless fly that lives alongside short-tailed bats and is a creature of nightmares for some.

Bat with a few hitch hikers.
📷: DOC, Louise McLaughlin

Bats are not the only endangered species we run into doing bat work. The New Zealand bat-fly Mystacinobia zelandica is a species of wingless fly that has evolved to live alongside short tailed bats. At some point they decided hitching a ride on the back of a bat was easier than flying and so lost their wings. Unfortunately, this gives them a somewhat spider like appearance which isn’t all that endearing, the first of their un-endearing traits.

Bat-fly having a meal on the go.
📷: DOC, Warren Simpson

Bat-flies are the housekeepers/ waste disposal workers in bat land. They have a symbiotic relationship where they feed on bat guano (bat dung) and keep things clean while the bats provide a warm safe environment with ample food. Females lay their eggs in large communal nurseries in the bottom of the guano pile and tend to the growing larvae.

Bat roosting tree from below.
📷: DOC, Jamie McAulay

However, life isn’t all peachy for bat-flies as there is a constant threat of being left behind at a roost tree when the colony moves on. Every evening when the bats depart, they must make a gamble on whether to stay or leave. Leaving means hitch hiking on a bat for the evening while the bat-flies all night, and staying means feeding at the roost tree. But once the colony moves away from a tree for the final time, any remaining bat-flies will slowly die as their food supply dwindles. This makes those stranded individuals pretty desperate to find a new home and when we climb the tree to take down our monitoring equipment, they swarm out seeking our heat, coming down the climbing rope to greet us.

Masses of bat-flies at a bat roost entrance.
📷: DOC, Colin O’Donnell

For us bat-flies are a part of life while we handle bats. They crawl off their hosts and onto us – on average there are about 5 per bat hanging on (though up to 30 on one individual have been seen). And while we endeavour to re-home as many as we can back onto the bats before release, come the end of the evening there are inevitably flies crawling around on our legs, in our hair, the back of a neck. We find them days later in our beds, packs, and even in a toothbrush…

A stranded juvenile with hitch hikers.
📷: DOC, Bex Jackson

Catch the team next time on the Conservation blog to take a closer look at the mighty trees that these bats roost in.

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 four we join the team just before Christmas, catching up and reviewing the monitoring footage.

More rain, more delays, we are starting to run out of time before Christmas. But there is just enough time for one final quick trip. Back at our roost tree we change the old batteries for new ones, swap the SD card and get a download from the data logger. Two transmitters are still in there but by now we aren’t sure if they are still on our bats or have dropped into the guano pile that fills the bottom of the roost cavity. Then we are off to climb and remove the video camera from another tree we had previously set up. The footage from here had only one lone bat departing, so it’s time to give up on this tree.

Radio Tracking.
📷: Warren Simpson DOC

Back at the hut we watch hours of footage counting bats and look at what’s on the datalogger. One of the questions we have about this colony is whether they have always been here hiding away, or whether they have branched off the Eglinton colony which is 40km away, a result of that population growing due to sustained predator control. In the new year we will be undertaking our annual monitoring of the Eglinton colony where over the past 15 years almost 3000 bats have been individually tagged with microchips, the same as the ones you put in your cat or dog. If the Ettrick Burn bats had split from the Eglinton colony then chances are some of them would have microchips.

Relaxing in the evening in our little home.
📷: Warren Simpson DOC

We have hand scanned every bat caught mist netting with no tags found, but the real test will be from the datalogger. At the tree we have set up an aerial around the roost hole to scan every bat as it flies in and out. When we look at the file it too comes up negative for tags. Maybe they have always been here, hanging on. It does makes you wonder, are there other little populations hanging on out there that we don’t know about? No one has ever conducted a proper search nation wide for short tailed bats.

Antenna, data logger and camera at a roost tree.
📷: Warren Simpson DOC

Our transmitter bats turn up in couple more trees, which when climbed leads to the transmitter sounding far off in some unobtainable limb, leaving us unable to tell if these trees are communal or not.

Making our transmitters, with snacks.
📷: Warren Simpson

More videos, more rain, the river is a torrent again. The bats stay roosting in our one known communal tree, though there must be another out there somewhere. And then it’s nearly Christmas, time to pack up and head home for the last time. In the end we collected 8 nights of useable video footage, but the count is never above the initial 207. For a short tailed bat colony this is small (the Eglinton counts are between 2000-3000) but it’s something, and the population is large enough that with sustained rat control it should be able to recover. However, it is too late for rat control to deal with the 2019 mast/plague but there are plans afloat for the next beech mast.

Climbing a mighty tree.
📷: Bex Jackson DOC

We make a final trip to our old faithful tree. The equipment on the tree comes down, then the tents packed up, the hut cleaned, and another game of tetris packing the helicopter. It’s goodbye for now, we hope to be back next year and find our bats hanging on.

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.