A devastating heatwave that scorched south-east Australia last week has claimed the lives of thousands of flying foxes, marking the most significant mass mortality event for the species since the catastrophic Black Summer of 2019-20.
A Scorching Toll on Vulnerable Colonies
Extreme temperatures, which saw consecutive days above 42°C in Adelaide and peaks in the mid-to-high 40s across suburbs and regional areas, proved fatal for flying fox colonies across three states. Grey-headed flying foxes, a species listed as vulnerable under national environment laws, were the worst affected.
Wildlife volunteers and researchers are still counting the dead, with initial estimates suggesting at least 1,000 to 2,000 deaths in South Australia, thousands in Victoria, and up to 1,000 in New South Wales. Tamsyn Hogarth, director of the Fly by Night Bat Clinic in Melbourne, described scenes of devastation at Brimbank Park, where volunteers discovered thousands of deceased bats.
"We also found countless adults who couldn’t withstand the heat in areas of the colonies that were hotter - like trees with less foliage and shade coverage, and the baking hot clay of the riverbank," Hogarth said. Rescuers worked tirelessly to save dozens of orphaned pups found clinging to their dead mothers, who would otherwise face a slow death from heat stress, starvation, or predation.
Experts Describe a 'Biblical' Scale and a Climate Warning
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." He confirmed this event as the most significant since the Black Summer, during which over 72,000 flying foxes died in eight separate extreme heat events.
The heat has a "double-whammy" effect, Welbergen noted. It places the animals under direct physiological stress while also impairing their ability to forage by making flight more difficult and reducing nectar availability in eucalyptus flowers. The loss disproportionately affects mothers and pups, making population recovery even harder.
Dr Wayne Boardman, a wildlife veterinarian at the University of Adelaide, described the bats' distress signals: "They fan their wings, they start to move down the trees, they pant a bit, some try to fly to dip in the river." However, beyond 42°C, survival becomes physiologically very difficult due to dehydration and heat stroke.
Volunteers at Breaking Point and a National Strategy Void
The crisis has placed immense strain on wildlife rescue networks. Lisa Palma, CEO of Wildlife Victoria, said 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 stated.
Professor Welbergen emphasised that flying foxes act as "canaries in the coal mine," their highly visible deaths in urban roosts signalling the hidden toll extreme heat takes on other wildlife as global heating intensifies.
Tamsyn Hogarth highlighted the systemic challenges: "We’ve been hit with a terrible season for orphaned pups. We were already at breaking point... now our worst fears have been realised." The burden falls heavily on volunteers and an under-resourced veterinary sector, with no national wildlife rescue strategy in place.
Authorities strongly advise the public never to attempt to rescue sick, injured, or orphaned bats themselves due to the risk of disease and injury, and instead to contact their nearest licensed wildlife organisation immediately.
