Last week’s extraordinary heatwave in south-east Australia caused the deaths of thousands of flying foxes – the world’s largest bats. It is the largest mass mortality event for these creatures since the horrific Black Summer of 2019-2020. In South Australia, Victoria, and New South Wales, extreme heat set the stage for a truly catastrophic scenario. This unprecedented heat put the bats under severe heat stress, leading to death and massive population collapses.
In South Australia, it was volunteers who documented the heartbreaking death toll of at least 1,000-2,000 flying foxes. To say the situation in Victoria was grim would be an understatement. At least thousands of animals died because of heat stress and up to 1,000 flying foxes perished in New South Wales. While these numbers are tragic, they can’t fully convey the reality loss on such a sweeping scale serves to underscore just how dire last week’s heatwave was.
The flying-foxes were in extreme discomfort as temperatures climbed beyond 42 degrees. Wildlife Rescue volunteers counted the thousands of flying fox carcasses at Brimbank Park. They turned up hundreds more dead at roosting sites in Yarra Bend and Tatura. Even with fierce determination from rescuers and volunteers working day and night to save as many clingy, orphaned pups attached to their dead mothers — the loss was unreal.
Prof. Justin Welbergen emphasized the lethal consequences of such high temperatures on flying foxes:
“Temperatures over 42 degrees are known to cause mortality in flying foxes, sometimes at biblical scales.”
The heatwave’s severity was its historic nature, Adelaide reached temperatures of 43°C on three days in a row. Wildlife experts soon concluded these unprecedented conditions had been disastrous not just for flying-foxes but other native wildlife. Lisa Palma remarked on the vulnerability of these animals during heat events:
“Heat events like this can be catastrophic for native wildlife. Unlike us, our native animals can’t escape the heat and are highly vulnerable to dehydration, disorientation, burns and even blindness.”
Dr. Wayne Boardman described the behavior exhibited by the flying foxes under duress:
“They fan their wings, they start to move down the trees, they pant a bit, some try to fly to dip in the river.”
This mass mortality event is a troubling reminder of the historic, current, and future challenges Australian wildlife will continue to face. Yet the human and material losses leave us with memories of other true catastrophic events. During Black Summer, more than 72,000 flying foxes died in just eight individual extreme heat events. In 2018, an unusually intense heatwave affected Queensland. It had a catastrophic impact on the population of endangered Spectacled Flying Foxes, killing 23,000 individuals—almost a third of their entire population at that time.
Tamsyn Hogarth, a wildlife volunteer, expressed her concerns about the current situation:
“We’ve been hit with a terrible season for orphaned pups. We were already at breaking point and dreading what the hot weather would bring – now our worst fears have been realised.”
Flying fox mortality has an acute impact especially in built up areas where this species congregates in high densities. Their decline stands testament to the ecological crisis in these tropical paradises. Prof. Welbergen, in referring to them as “the canaries in the coal mine,” stressed their importance in helping us understand larger environmental threats.