Friends of Grasslands & microbats

A fascinating evening talking all things (micro) bat with Michael Pennay, from NSW National Parks and Wildlife Service, and Friends of Grasslands - FOG. Many thanks for organising, Margaret and Andrew

Four 'harp traps' were set up for the previous night so the group was able to look at these amazing small flying mammals at first hand.

Australia has around 60 species of microbats, most feeding on insects (in large numbers).

Bat trapping at Wandiyali - Friday 17 March 2023

Margaret Ning & Andrew Zelnik

Edited: Michael Pennay

Setting the scene

 “On the evening immediately prior to our bat activity, three of us joined bat expert, Michael Pennay who works for NSW National Parks and Wildlife Service to identify optimal places in which to set up harp traps for our bat activity the following evening. We were on the environmental gem of Wandiyali, near Googong, with its owner Carolyn. The privately owned property contains some lovely grassy woodland which was superbly appropriate for our proposed activity, and four harp traps were duly assembled.

The following morning Michael, accompanied by Carolyn, gathered the bats that were trapped overnight, and dismantled three of the traps. Throughout Friday, those bats slept safely in torpor through the day as usual snug in a bag carefully looked after by Michael.

Come Friday evening…...

At 7pm, 15 of us assembled in the fading light of a lovely grassy woodland area of Wandiyali, and Michael immediately started sharing his bat knowledge. 

Bats can live more than 30 years, they only have one young at a time, although some can have twins.
We walked the short distance to the remaining harp trap, and Michael explained how it works.

The information flow continued: bats don’t carry any fat, they go into torpor when it’s too cold or windy. There used to be a split between ‘mega’ and ‘micro’ bat species, but this doesn’t hold up any more. Some bat species call out of their mouths and others out of their noses. The range for carnivorous ghost bats is limited these days to northern Australia but it used to be in central Australia. Another species the Large -footed Myotis has huge toes with which to catch aquatic prey, which are utilised on big open water sources, like the Queanbeyan River, where they can get a good run. They scoop up their prey, hold it in their toes, and eat while on the wing.

It is possible to catch ghost bats in harp nets. Most Australian bat species live in tree hollows. The entrances they utilise can be tiny, and preferably only head size, in order to keep out predators. Not all bats can ‘hold’ tracking transmitters used to study their movements and behaviour. The latter weigh a quarter of a gram, which is a big percentage of the bat’s body weight.

 Michael introduced us to the first of the two bat species trapped overnight in the harp traps. It was a Little Forest Bat (Vespadelus vulturnus)(right) which is really tiny, and contender for the smallest mammal in Australia. A fully grown adult is one tenth the weight of a mouse or about that of  a10c coin.

Bats have really thin bones, and have to be handled very very delicately. Somehow Michael handled the bat, while at the same time exerting no pressure.

Bat viruses….. There are two known bad viruses in Australia affecting both big and small bats, including the Australian Bat Lyssavirus and Hendra virus.  The Lyssavirus is related to rabies and makes the bats sick, it is virtually 100% fatal to mammals it infects. The Hendra virus doesn’t seem to affect the bats at all but can spread to people through an intermediary host (horses) where it can make both horses and humans very sick and sometimes is fatal. Although we don’t have rabies in Australia, Michael is vaccinated against it, which also prevents lyssavirus infection. But Michael assured us that a feisty wild bat is less likely to be a danger to us, as bat trappers and observers. More at risk are wildlife carers who help bats which may be ill or injured. Gloves are essential attire.
Bats do not seem to be put off by the noise and movement of people walking around underneath them.

The second of our captured bat species was a Large Forest Bat (Vespadelus darlingtoni)(left), which weighs about seven grams (around weight of a $2 coin). Both our captured bat species had wingless bat flies on them, which do not seem to bother them, but maybe indicates that they are from a bigger colony. Most of of the wingless bat flies (Diptera: Nycteribiidae and Streblidae) specific to individual bat species, and the bat flies themselves have specific microparasites and microorganisms that only occur on their species.

 The main predators of bats are birds like currawongs, kookaburras, tawny frogmouths, and  snakes and goannas. Bats are normally taken from their roost sites, or sometimes when they are too late or early and are caught out of the roost in the light.  Gould's wattled bat (Chalinolobus gouldii) and its cousin the Chocolate Wattled bat (Chalinolobus morio) sometimes leave the roost earlier in the evening, especially in Autumn , and can be seen against the twilight, but most species usually wait until complete darkness to avoid bird predators.

Before departing on an evening’s hunting, bats need to warm up to enable them to fly. Michael was able to demonstrate this as he released the species he had trapped the night before, just before 8pm. He held one in his hand, listened to it ultrasonic ‘cheep' on a bat detector and off it flew. Undaunted by its brief experience in captivity, one began chasing some food straight away!

Michael told us about other bat species, including the eastern bent wing bat that roosts in caves. Apparently they don’t seem to mind the cold in winter and sometimes seek it out to help them sleep (hibernate) better. Some species of bats have been recorded flying up to 4.5km above ground level.

After the captured bats were released, we were provided with acoustic detectors, with which to walk down a track and see what we could hear. We added a White striped mastiff bat (Austronomus australis) to our list. To finish off the evening, we then dismantled the final harp trap. Even while packing up the final trap, Michael was still imparting info, although we did not feel we were on overload as it had been such a casual relaxed evening.”