• Ian

Micro bats

Updated: Feb 13

Bats can be divided into two main groups, micro bats and mega bats.

Mega bats, like flying foxes, are the bats we often see flying off to feed at dusk or hear them feeding on blossoms or fruit at night. They are relatively large, thus the mega in mega bat.


Micro bats are much more illusive. They are small, some only as big as your little finger and mostly roost in caves or sometimes behind bark out of sight.


Nearly all micro bats can't be heard by humans as they use high frequency sound, outside our hearing range, to navigate and catch prey at night somewhat like a radar. They create the sound and listen for the echo off things. This is called echolocation. You will notice the extra large ears of these animals used to pick up these bounced ultra high frequency sounds they emitted.


You can see these bats in the last light, flying through the air catching insects. We even managed to get a photo of one that roosted in a shed, which we believe to be the Scotorepens orion.


Micro bats tend to feed in particular environments which they are best adapted to. Some will feed above the forest canopy, others below the canopy or some even go fishing over water using their large feet to grab water insects or small fish.


Microbats often form colonies when roosting during the day. Many bats will be described as roosting in caves but where caves are not common they will roost in tree hollows.


They are mammals and so feed their young on milk. The females can form maternity colonies where young are raised in colonies of sometimes thousands of young huddling together for warmth while their mothers feed.


Bat Detector

Since micro bats are difficult to see at night and we can't hear most of them they are difficult to identify. The echolocation sounds however do distinguish between species, each with its own distinct high frequency sound patterns. A bat detector can record these high frequency sounds. Some detectors allow these sounds to be exported and can be viewed as a graph which can then be cross checked against a database of graphs for each of these bats.

If you are interested in the graphs and more on bat identification check this link.

Many thanks to Dr Dave Sharpe for the bat detector and setting up and analyzing the results from the device. Dave put out the device in the late evening and through the night where it listens to the ultra sounds from the bats and records them for later analysis.

The bat detector range is limited so the recordings only detect bats relatively close to the device.

Dave has been able to identify nine micro bats recorded in this single session. It is likely that other bats, like the one photographed but not in these recordings, are also present.


Istari Micro bats

These micro bats have been identified by photo or bat detector and include a little information on each of them. There are some excellent websites with a lot more information. Our favourite is All about Bats of Southern Queensland which contains all the bats so far found. There are more links at the end.


Broad nosed bat

(possibly Scotorepens orion)

http://www.allaboutbats.org.au/eastern-broad-nosed-bat/

We are unsure of this bat as it has only been photographed. We have not got a recording making it difficult to identify. This micro bat usually lives in tree hollows but this bat was found in our shed, roosting in an old coat.

It is distributed along the east coast of Australia. It is a medium sized bat.


East-coast freetail bat

(Mormopterus norfolkensis) - All About Bats - East Coast Freetail bat https://www.allaboutbats.org.au/east-coast-freetail-bat/

The East-coast freetail bat is found east of the Great Dividing Range from north of Brisbane to the southern NSW border. They feed on insects above the trees and along the edges of forests. They roost in tree hollows and sometimes in human constructions.

They are considered vulnerable in NSW.

It is a tiny bat weighing up to 10gms and big enough to hold in a few fingers.


Eastern bentwing bat

(Miniopterus orianae oceanensis) - All About Bats - Eastern Bentwing Bat

https://www.allaboutbats.org.au/eastern-bent-wing-bat/

The Eastern bentwing bat roosts in tree hollows or caves or similar refuges, including human constructions. They are considered vulnerable in NSW. They feed on insects like flies and cockroaches.

Females sometimes form large maternity colonies.

The head and body length is 10–11 cm.

They roost in small colonies.


Eastern cave bat

(Vespadelus troughtoni) - All About Bats - Eastern Cave Bat

https://www.allaboutbats.org.au/eastern-cave-bat/

https://australian.museum/learn/animals/bats/eastern-cave-bat/

The Eastern cave bat, not surprisingly tends to roost in caves. They are a vesper bat which

They feed on insects catching their prey in the membrane behind their legs and passing it to the mouth.

Maternity colonies can reach over 200 adults. The colony is set up by the pregnant females who give birth around the same time and keep the young warm in these colonies feeding the young milk like other mammals. The colony will eventually disband when the young leave the colony.