The Goulburn Broken Catchment Management Authority is highlighting the importance of tree hollows for wildlife in its 2025 Year of the Tree Hollow community awareness campaign.
This month features the tiny microbats of the catchment which includes Gould’s Wattle bat, Gould’s Long-eared bat and the Lesser Long-eared bat.
Goulburn Broken CMA project officer, Janice Mentiplay-Smith, described microbats as amazing mammals of the air.
“Fast and feisty little microbats dart through the night sky, leaving their roosts at dusk to pursue their insect-based dinner,” Ms Mentiplay-Smith said.
“In a single night microbats can eat at least one third of their body weight, with mosquitoes featuring strongly on the menu. Multiply this by many, many thousands of microbats and it’s not difficult to see how these tiny flying mammals provide a valuable ‘pest control’ service.”
Ms Mentiplay-Smith said microbats roost in tree hollows, behind pieces of bark and in caves.
“Dead trees are vitally important for microbats as they contain plenty of hollow spaces for roosting,” she said.
“Even small dead trees with trunks of just 20-centimetres in diameter are extremely valuable as they have small hollows and cracks where microbats can squeeze into. So, it’s important we do everything we can to preserve these precious resources.”
The lack of tree hollows in the landscape means microbats must find alternative roosts such as cracks in fenceposts, storm water pipes, culverts and within house and shed roofs and walls, none of which are ideal.
Microbats are placental mammals and not marsupials - they do not have a pouch and give birth to fully developed young. Including those inhabiting the Goulburn Broken catchment, there are more than 60 species of microbat in Australia.
Microbat babies are called pups and are born in late spring and feed on their mother’s milk until mid-summer. At birth, the pups are approximately one-third the size of their mother; the equivalent of a human giving birth to an approximately 20-kilogram baby!
“These tiny mammals weigh between 3-150 grams, depending on the species. All microbats use echolocation ‘pulses’ to locate and gauge the distance between themselves and other objects, including prey,” Ms Mentiplay-Smith said.
“They emit a sound and listen for it as it bounces back. The time taken for the pulse to return indicates the location of the object. Normally a microbat emits about 10 pulses per second. When an insect is detected, these pulses increase to more than 100 per second.
“During summer and autumn when insects are plentiful, microbats fatten up in readiness for winter. Once the nights become cooler and insects disappear, microbats lower their body temperature and enter a torpor, a form of short-term ‘hibernation’. This way they can survive by drawing energy from their stored fat until spring.
“If you know the location of microbats settled into their torpor over winter, be careful not to disturb them. Emerging from torpor too soon subjects them to predation and forces them to draw on valuable fat reserves. If disturbed too many times they will deplete their stored energy and won’t live until spring.”
Read more about microbats in the Goulburn Broken CMA’s The Mammal Book, a 58-page booklet featuring beautiful photographs and informative text. The Mammal Book - GB CMA - Goulburn Broken CMA
Visit https://www.ausbats.org.au/bat-nights.html to find out about informative bat night and https://ausbats.org.au for information on how to build and install a bat box.
The Year of the Tree Hollow is supported by the Victorian Government through the Our Catchments Our Communities stewardship program.
Gould’s Wattle Bat, Gould’s Long-eared Bat and Lesser Long-eared Bat. Photos by William Terry.