Thousands of flying foxes have died in a recent heatwave that affected south-east Australia. This event represents the largest mass mortality for flying foxes since the 2019-2020 Black Summer season.
Impact of Extreme Temperatures
Extreme temperatures led to deaths across camps in South Australia, Victoria, and New South Wales. Grey-headed flying foxes, a species listed as vulnerable under federal environmental laws, were the most impacted.
Volunteers from the Fly by Night Bat Clinic in Melbourne observed thousands of deceased bats at Brimbank park and hundreds more at camps in Yarra Bend and Tatura. Wildlife volunteers provided assistance, rescuing dozens of pups found clinging to dead mothers. These orphaned pups face risks of heat stress, starvation, or predation if not located.
Estimates indicate that at least 1,000 to 2,000 flying foxes died in South Australia, thousands in Victoria, and up to 1,000 in New South Wales.
Expert Observations
Professor Justin Welbergen, a flying fox expert at Western Sydney University, stated that temperatures exceeding 42 degrees Celsius are known to cause significant mortality in flying foxes. He identified the recent loss of life as the most substantial mass mortality event since 2019-2020.
During the Black Summer, over 72,000 flying foxes perished across eight extreme heat events. A heatwave in 2018 resulted in the deaths of 23,000 endangered spectacled flying foxes in Queensland, which constituted one-third of their population at that time.
Last week, Adelaide recorded temperatures of 43C on consecutive days, while Melbourne and Sydney experienced temperatures above 42C on their hottest days. Regional areas reported maximums in the mid-to-high 40s.
Professor Welbergen noted that the heat caused a "double-whammy" effect, directly stressing animals and hindering their ability to find food due to difficulty flying and reduced availability of nectar from eucalyptus flowers. Mothers and pups were particularly affected, potentially impacting population recovery.
Dr. Wayne Boardman, a wildlife veterinarian and researcher at the University of Adelaide, described the initial signs of distress in flying foxes, including wing fanning, moving down trees, panting, and attempting to dip into rivers. However, temperatures above 42C make survival physiologically difficult.
Public Advice and Broader Implications
The public is advised not to attempt rescuing sick, injured, or orphaned bats themselves but to contact their nearest wildlife organization.
Lisa Palma, Chief Executive of Wildlife Victoria, confirmed that the organization increased its emergency response capacity and deployed its veterinary service to a critical flying fox colony. She stated that such heat events can be catastrophic for native wildlife, as they are vulnerable to dehydration, disorientation, burns, and blindness.
Professor Welbergen commented that flying foxes serve as indicators of environmental conditions, much like "canaries in the coal mine," highlighting the impact of increasing frequency and intensity of hot days and heatwaves on other wildlife. The rescue and care efforts place a significant burden on volunteers and under-resourced veterinary services, with no national wildlife rescue strategy in place.