A devastating heatwave that scorched south-east Australia last week has resulted in the deaths of thousands of flying foxes, marking the most significant mass mortality event for the species since the catastrophic Black Summer of 2019-20.
A Catastrophic Toll on Vulnerable Species
Extreme temperatures, which saw consecutive days above 42°C in Adelaide and peaked in the mid-to-high 40s across suburbs and regional areas, proved fatal for colonies across South Australia, Victoria, and New South Wales. The grey-headed flying fox, a species listed as vulnerable under federal environment laws, was the most severely affected.
Volunteers from the Fly by Night Bat Clinic in Melbourne discovered a harrowing scene. Thousands of dead bats were found at Brimbank Park, with hundreds more casualties recorded at camps in Yarra Bend and Tatura. The clinic's director, Tamsyn Hogarth, described rescuing dozens of orphaned pups found clinging to their dead mothers. "These orphans will slowly die of heat stress, starvation or predation if they aren’t found," she said.
Researchers are still counting the losses, with initial estimates suggesting:
- At least 1,000 to 2,000 deaths in South Australia.
- Several thousand in Victoria.
- Up to 1,000 in New South Wales.
Why Flying Foxes Are So Vulnerable
Professor Justin Welbergen, a flying fox expert at Western Sydney University, explained that temperatures exceeding 42°C are known to cause mortality "sometimes at biblical scales." The heat has a "double-whammy" effect, directly stressing the animals while also impairing their ability to forage by making flight difficult and reducing nectar availability from eucalyptus flowers.
Dr Wayne Boardman, a wildlife veterinarian at the University of Adelaide, noted the animals' distress signals before succumbing. "They fan their wings, they start to move down the trees, they pant a bit, some try to fly to dip in the river," he said. However, beyond 42°C, dehydration and heat stroke make it "physiologically very difficult for animals to survive."
Mothers and pups were disproportionately affected, a factor that will hinder population recovery. This event echoes previous tragedies, including an extreme heatwave in 2018 that wiped out 23,000 spectacled flying foxes in Queensland.
A Warning Sign and a Strain on Rescuers
Professor Welbergen emphasised that flying foxes act as "canaries in the coal mine," providing a visible indicator of the plight of other wildlife as climate change increases the frequency and intensity of heatwaves. The animals' tendency to roost in large, visible urban colonies makes their deaths particularly conspicuous.
The crisis has placed immense pressure on wildlife rescue networks. Lisa Palma, CEO of Wildlife Victoria, stated the organisation boosted its emergency capacity, deploying a travelling veterinary service to a nationally critical colony. "Heat events like this can be catastrophic for native wildlife. Unlike us, our native animals can’t escape the heat," she said.
The burden falls heavily on volunteers and an under-resourced veterinary sector. Tamsyn Hogarth summed up the desperate situation: "We were already at breaking point and dreading what the hot weather would bring - now our worst fears have been realised." The public is urged never to attempt to rescue bats themselves due to disease risks, but to contact professional wildlife organisations immediately.
