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Microbats under the microscope

Microbats are often not seen or heard, but there are thousands of them in the Mallee bush and when habitat like the Hattah Lakes are in good health, they can thrive.

Published: 11 March 2022

You very rarely see them as they make no audible noise, are tiny, and active only during the warmer months at night.    

Microbats are the most common and diverse mammal group in the Mallee bush and the floodplains.   

The Mallee Catchment Management Authority (CMA) team, through The Living Murray joint initiative, is working with The Arthur Rylah Institute to undertake a Before After Control Impact study to measure bat activity levels and species richness to gauge their response to water for the environment.  

The study commenced in 2020–21 at the Hattah Lakes Icon Site when only one lake contained water, Lake Kramen, providing the 'before' conditions. Autumn and spring watering events allowed 18 lakes to receive water for the environment during 2021 with bat monitoring occurring over the summer period, providing the 'after' conditions.  

With all 18 of the lakes receiving water for the environment, an abundance of flora and bug populations was created, perfect for the microbat.  

The Mallee CMA aims to identify the microbat species inhabiting the Hattah Lakes system and quantify the change in diversity and activity of microbats around wetlands following the delivery of water for the environment. This includes addressing the questions:  

  • Is there a difference in microbat species richness and activity before and after environmental water delivery? 
  • Is there a difference in microbat species richness and activity between lakes? 
  • What microbat species are inhabiting the Hattah Lakes Icon Site? 

The study involves capturing microbats during the evening using mist nets and harp traps. This allows scientists to record information including species, size and gender. 

There is little known about microbats in the Mallee region in comparison to other animals and bat species generally have different calls to the same species in a different region. The researhers will record the bat calls and continue to develop the Hattah Lakes call library so they can be identified by their calls in the future. 

Many microbats are insectivorous, meaning they eat insects, and they can catch up to 500 insects an hour and eat up to half their body weight each night.  

Microbats do make sounds but at a frequency outside of the human ear’s hearing range.  As these bats are nocturnal and do not have the best eyesight, they use echolocation for flying around at night and hunting insects.  

Microbats create sound waves in the bat’s voice box and are emitted from the mouth or the nostrils. The echo that comes back to the bat indicates how far away the object is, as well as its size and texture, and if it’s moving. 

This echolocation is similar to how whales and dolphins emit sound waves underwater.  

Many bat species are sensitive to habitat changes and other kinds of disturbance, and microbat populations around the world have been in decline for several decades.   

Bats rely heavily on the floodplain for insect prey, drinking water and hollow‐bearing tree for roosting. The density and health of trees on and around the floodplain benefit from environmental watering, with the flow on impact providing significant benefits for the animals that rely on them. 

The Mallee CMA will be publishing the results of the study and used to inform future water for the environment planning. 

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