Southern bent-wing bat: good things come in small (bat) packages

Name: Southern bent-wing bat (Miniopterus orianae bassanii)

Size: Average length approximately 5 cm (including head and body), average weight 15g

Diet: Flying insects, especially moths

Habitat/range: Southwest Victoria and southeast South Australia

Conservation status: Critically endangered

Superpower: Mass insect muncher! Each night, colonies collectively gobble hundreds of kilos of flying insects, such as moths and mosquitoes.

The southern bent-wing bat was Australia’s Mammal of the Year for 2022!

The Southern bent-wing bat is a placental mammal like you and me – plus amazing adaptations for flight, with their wing membranes stretching across their elongated fingers. All this in a tiny 15-gram package. That’s the same weight as a 50-cent coin!

They can see, but they also use echolocation to hunt and navigate by sound – which is helpful when you’re catching flying insects at night. These abilities also enable the bats to spend their days up to hundreds of metres underground in caves in complete darkness, where the temperatures are often mild and relatively stable all year round.

Southern bent-wing bats regularly use ‘torpor’ to drop their body temperature and metabolic rate to save energy. And when a female becomes pregnant in autumn, she delays the implantation of the fertilised egg and the subsequent development of the embryo until spring, when the above-ground temperatures are warmer and there are more insects around.

Photograph of a southern bent-winged bat flying on a black background
A diminutive Southern bent-wing bat. Credit: Steve Bourne via Wikimedia Commons.

This species is highly social and knows a thing or two about working together. Populations are centred on just three ‘maternity’ caves within a restricted geographical range, where the bats give birth and raise their young.

By congregating in large numbers at one of their key maternity caves at Naracoorte Caves World Heritage Area, they can transform the conditions in the maternity chamber of the cave, making it more humid and up to 12 degrees warmer. These changes are thought to help with the development of the young – much like a humidicrib for human babies.

At night, mothers leave their pups clustered on the cave ceiling in a ‘creche’ while they go out to hunt for moths, including agricultural pests. The bats can fly more than 70 kilometres in just a few hours.

When the mother returns from foraging, she knows exactly which pup is hers among the hundreds of others. What’s more, she will continue to nurse until the pup is the same size as she is, or even heavier. This is presumably to give the young the best possible chance of survival as they become independent and need to find food for themselves.

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Southern bent-wing bat populations rely on individuals having very high survival rates, because females only have one pup a year. One female was recaptured in the wild when she was at least 22 years old and she was still breeding!

But drought, widespread loss of foraging habitat, and disturbance or loss of caves are among several threats to this species. Our best available data suggests that if current survival rates continue, the total population could decline by up to a further 97% over the next few decades.

Urgent action is needed to reduce extinction risk of this critically endangered species and ensure its survival. A National Recovery Team has already formed to help conserve the Southern bent-winged bat. However, a huge factor contributing to conservation success is public awareness and support. Can we rally behind the Southern bent-winged bat to give it the spotlight and conservation action it deserves?

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