Australian research illuminates the effect of streetlights on microbats

Artificial lighting affects Australian microbats in vastly different ways, sending one species flying for cover, while another forages among the attracted insects, according to new research.

Researcher Rani Davis from the University of Queensland placed acoustic detectors in ten bushland and parkland areas across the capital, Brisbane, recording the echolocation calls of two species of microbats – the White-striped free-tailed bat (Austronomus australis), and the Little bent-wing bat (Miniopterus australis) – at increasing distances from artificially lit pathways.

Using the acoustic detectors, Davis was able to identify which species were present and how their flight activity changed according to increasing distance from streetlights.

M. Australis a. Australis spectrogram rani davis
Spectrogram showing the difference in echolocation calls of A. Australis and M. Australis / Credit: Rani Davis

Her study is the first to investigate how the activities of different Australian insectivorous bats change based on distance from artificial lighting.

Austronomus australis. Credit australian museum 1
White-striped free-tailed bat / Credit: Australian Museum

Davis was surprised to find the responses of the two species almost completely at odds.

While the Little bent-wing bat steered clear of the lit areas, and was much less active even up to 50m away from the light source.

The activity of the White-striped freetail was largely unaffected. Davis expects this is because the species can fly fast enough to catch the insects attracted to the lights, and still manage to evade predators, such as owls.

Artificial lighting affects many nocturnal and light-sensitive animals, by fragmenting the environment in a similar way that structural features like roads and fences can, Davis says.

She hopes the work will inform streetlight design in Australia to better protect urban wildlife, like microbats.

Miniopterus australis. Credit australian museum
Little bent-wing bat / Credit: Australian Museum

“In urban areas flooded with streetlights, light-sensitive species may experience limited ability to move across the landscape, which could lead to their populations becoming stressed,” she says.

In Europe and the UK, best practice guidelines on bat-sensitive lighting provide information on assessing, designing and selecting technologies to minimise these effects.

Davis presented her research at the Ecological Society of Australia Conference 2023 on Wednesday.

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