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  • Writer's pictureIan

Micro bats

Updated: Feb 13, 2022

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

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

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

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.

They can be found north of Sydney to Queensland border and west to the Pilliga.

They are considered vulnerable in NSW.


Gould’s wattled bat

(Chalinolobus gouldii) All About Bats - Goulds Wattled Bat

These bats are widely distributed throughout the continent. They also feed on insects. They are larger than the other microbats growing to around 70 mm long with an average mass is 14gms.

They live in caves in colonies up to 200.


Hoary wattled bat, Broad-nosed bat

(Chalinolobus nigrogriseus)

The Hoary wattled bat is generally found in northern and east coastal regions in NSW, north of Port Macquarie.

They are vulnerable in NSW.

They are about 45-55mm for head and body long less than the little finger

They roost in tree hollows and rock fissures. They feed off insects, flying below the canopy where the understory is less dense.


Large-footed myotis, Fishing bat

(Myotis macropus)

The Large-footed myotis or fishing bat is another vesper bat. It uses its extra large feet to fish for aquatic prey in water, grabbing the prey from the water and transferring to its mouth.

This bat is vulnerable in NSW. It weighs up to 15gms. Its large foot is around 8mm long. They live in small colonies of 10-15 usually roosting in caves near water.

They are distributed along northern and eastern Australia to southern Victoria within about 100km of the coast.


Little bentwing bat

(Miniopterus australis)

The little bentwing bat is another vesper bat. It is distributed along the east coast and is considered vulnerable in NSW

It is a small bat with a body length of only 45mm.

It roosts in caves and forms colonies sometimes with other bats like Common bentwing-bats. Females will form maternity colonies sometimes with other bats like Eastern bentwing-bats. It feeds on small insects beneath the canopy of densely vegetated habitats.


White-striped free-tail (mastiff) bat

(Austronomus australis) - previously Tadarida australis

The white-striped free-tail bat is one of the few micro bats whose echolocation is audible to the human ear making a 'ting ting ting' sound.

These bats average a weight of 37g. They fly high above the ground in search of moths grasshoppers and other insects.

They are tree dwelling bats. They are usually solitary but have been known to form small colonies of 10 but the females can forms large maternity colonies.

They are widely distributed across the continent except for the north.


Links


Updated 23 April 2021

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