White-striped free-tailed bat: spectacular sonar in a party-sized package

Name: White-striped free-tailed bat (Austronomus australis) 

Size: Bodies can be up to 10cm long, with a 40cm wingspan. Weighs 36g.

Diet: Flying insects, including moths and mosquitoes.

Habitat/range: Central and southern mainland Australia.

Conservation status: IUCN Least Concern.

Superpower/fun fact: This bat’s echolocation allows it to ‘see’ in the dark further than any other Australian bat.

Ting-ting… ting-ting… That’s the sound of the white-striped free-tailed bat searching for insects in the night sky. 

White-striped free-tailed bats are a small species of bat which can be seen, and heard, across most of mainland Australia. With striking, and rather fashionable, white stripes of fur just under their wings, it is hard to mistake this bat for any other. The species is made even more unique by its distinctive echolocation calls, as one of the few microbat species which emit calls within the human hearing range. These calls are emitted at a lower frequency than any other native bat species, allowing them to travel greater distances than the calls of other bat species.

Audio recording of navigational calls. Image is a spectrogram of navigational calls visualised in Kaleidoscope Pro. Credit: Harry Rust

Why is this? It’s because lower frequency sounds travel further. You will have heard evidence of this if you have ever driven past a concert or music festival and noticed that you can hear the sound of the bass first, then as you get closer, you can hear the other instruments.

The bat calls bounce off the surface of anything they come into contact with, creating echoes which the white-striped free-tailed bat can use to navigate and locate prey in the night, allowing the bat to discern the shape, size, and even texture of prey insects from great distances, even in complete darkness.

The bat will often eat half its bodyweight’s of flying insects in a single night making this species hugely beneficial for farmers,  reducing the amount of pest insects eating agricultural crops. This bat also provides the great benefit of reducing mosquito populations, something all Australians can be thankful for!

During the day, this bat gets cozy, sleeping in the old tree hollows and under loose bark, usually roosting amongst hundreds of other bat-friends and family in its colony. These species are picky tenants however, usually moving to a new house every ten days, exploring new regions with new insects to snack on. When these bats find a treehouse that is particularly luxurious, they set up a maternity roost, where they give birth and raise their young. This usually happens around Mid-December to late January. Each bat-mum has one pup every year.

Deforestation, and clearance of native vegetation is displacing the white-striped free-tailed bat. Building bat-boxes can help provide homes for these bats and raise awareness of their presence in our backyards across the country, however, man-made roosts cannot compare to natural tree hollows which can take decades to form naturally, so it is of great importance that we take care of our old-growth trees!

---

Voting for Australian Mammal of the Year 2023 is now open!

More information about the voting process can be found here.