26 Mar 2021


A successful trial of an atmospheric cooling system for flying foxes has given hope to researchers working to prevent the vulnerable species from dying and suffering in Australia’s extreme heat.

The innovative cooling system was installed in January in Bendigo’s Rosalind Park, which is home to an important breeding colony of grey-headed flying foxes.

Jointly funded by WWF-Australia, the City of Greater Bendigo, and the Department of Land, Water, Environment and Planning, the system comprises a series of aerial sprinklers in the tree canopy that distribute rain-like droplets on extremely hot days.

In addition to keeping the flying foxes cool, the system is also designed to reduce heat stress among plants and tree ferns in the park.

The system was trialled for the first time this summer over three days from 23 - 25 January when temperatures climbed as high as 41 degrees.

Data logging devices show the temperature in the test zone dropped by up to 2 degrees and the heat stress index also dropped. No flying fox deaths were recorded.

City of Greater Bendigo’s Coordinator Heritage Gardens and Amenity Landscapes, Orrin Hogan said researchers also observed positive behaviours from the flying foxes.

“Some flying foxes were a bit startled when the system first activated, but we soon saw individuals moving closer to the sprinklers, stretching out their wings and licking water droplets,” said Mr Hogan.

There were very different scenes at Rosalind Park in the summer of 2020 when up to 220 flying foxes died from heat stress when temperatures soared past 40 degrees. It was one of a series of mass mortality events in eastern Australia caused by a record-breaking heatwave.

Flying foxes often experience fatal heat stress when temperatures eclipse 42 degrees. The threat to the species is growing, with climate change driving more extreme heat events.

“Climate change is the single greatest threat to Australia’s flying foxes and the problem is only going to get worse,” said Dr Rodney van der Ree, an ecologist at WSP Australia who is overseeing the cooling system trials.

“I often go to flying fox camps after a heat event and the scene is quite confronting. I’m meant to be an objective ecologist, but when you see thousands of dead bats lying on the ground it’s impossible to be unaffected.”

While the cooling system requires further testing, Dr van der Ree said he hoped it could be replicated at other sites to protect flying fox colonies.

WWF-Australia’s Threatened Species & Climate Adaptation Ecologist, Dr Kita Ashman said flying foxes were a polarising but important species.

“Australia has a love-hate relationship with flying foxes, but without them many of our forests and woodlands would not be the same. They help to disperse seeds and pollinate our flowering plants, so we need to think outside the box to protect them from heat events,” said Dr Ashman.

WWF-Australia shared the results of the cooling system trials in the lead up to Earth Hour 2021 to raise awareness of the impact of climate change on Australia’s biodiversity.

This year Earth Hour is encouraging people to sign up and support Australia’s switch to an economy based on renewable energy to reduce our contribution to global emissions and climate change.

“Native species like flying foxes don't have a voice. They can’t sign a petition, so we have to do what’s right for the places and animals we love by calling for stronger action on climate,” said Dr Ashman.

People can sign up to make the switch for nature this Earth Hour on Saturday 27 March at 8:30 pm local time at earthhour.org.au