A recent period of extreme heat and associated bushfires across south-east Australia has resulted in significant wildlife mortality, particularly among flying fox populations. Thousands of grey-headed flying foxes have died in what is described as the largest mass mortality event for the species since the 2019-2020 Black Summer. The events have also impacted other native species, affected farm animals, and strained wildlife rescue services across Victoria and other affected states.
Impact on Flying Fox Populations
Thousands of flying foxes perished during a recent heatwave affecting south-east Australia. This event represents the most substantial mass mortality for flying foxes since the 2019-2020 Black Summer season, when over 72,000 flying foxes died across eight extreme heat events. Grey-headed flying foxes, listed as vulnerable under federal environmental laws, were the most impacted species.
Deaths were observed across camps in South Australia, Victoria, and New South Wales. 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. In Victoria, concentrations of bat deaths were reported in areas including Echuca, Tatura, and Numurkah in the state's north-east, as well as the Yarra Bend Park colony in Melbourne, where an estimated 1,000 baby flying foxes died within a week. Tamsyn Hogarth of Fly By Night, a volunteer organization, reported a ratio of three deceased flying foxes for every live baby flying fox found.
Professor Justin Welbergen, a flying fox expert at Western Sydney University, stated that temperatures exceeding 42 degrees Celsius are known to cause significant mortality. Dr. Wayne Boardman, a wildlife veterinarian at the University of Adelaide, noted initial signs of distress in flying foxes, including wing fanning, moving down trees, panting, and attempting to dip into rivers, but described survival above 42C as physiologically difficult. Professor Welbergen also reported that the heat directly stressed animals and hindered 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.
Broader Wildlife Effects and Bushfire Impacts
In addition to the heatwave's direct effects, bushfires in Victoria impacted over 400,000 hectares. The Victoria Department of Energy, Environment and Climate Action (DEECA) deployed teams to locate injured wildlife in fire-affected areas statewide. Other species impacted by the combined effects of heat and fire included koalas, kangaroos, wallabies, possums, and native birds. Heat-stressed animals also exhibited increased incidents such as vehicle collisions, entanglements, and other injuries.
Individual accounts illustrate the challenges faced by animal care providers. Kathy Munslow, who operates an animal sanctuary near Gobur, Victoria, evacuated ahead of an approaching bushfire, leaving approximately 75 rescued farm animals. Upon returning, her home was undamaged, but a shed and significant portions of her land were burned, with one cow requiring euthanasia. Robyn Coy, owner of Tarcombe Wildlife Shelter, escaped a fire in Longwood, Victoria, with a dog, three joeys, and a deer, taking refuge in a dam as her shelter was consumed. A fundraising campaign organized by Ellie Stubbs to assist Ms. Coy raised over $344,000.
Temperatures and Historical Context
The recent heatwave saw Adelaide record 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.
Previous extreme heat events have also resulted in significant flying fox mortality. A heatwave in 2018 led to the deaths of 23,000 endangered spectacled flying foxes in Queensland, representing one-third of their population at that time.
Volunteer and Emergency Response
Wildlife Victoria reported a record increase in public calls during the recent high temperatures, with calls increasing from an average of 350-400 per day in January to 1,135 on January 9. Lisa Palma, CEO of Wildlife Victoria, stated that the organization increased its emergency response capacity and deployed its veterinary service to critical flying fox colonies. Volunteer teams provide guidance or refer callers to specialist services. While initial calls focused on heat-stressed animals, the priority has shifted to wildlife with burns following the bushfires. High call volumes are anticipated to continue.
The public is advised not to attempt rescuing sick, injured, or orphaned bats themselves but to contact their nearest wildlife organization. Wildlife volunteers, such as those from the Fly by Night Bat Clinic in Melbourne, provided assistance by rescuing dozens of pups found clinging to dead mothers. These orphaned pups are at risk of heat stress, starvation, or predation if not located.
Professor Welbergen noted that rescue and care efforts place a significant burden on volunteers and under-resourced veterinary services, with no national wildlife rescue strategy currently in place. He also commented that flying foxes serve as indicators of environmental conditions, highlighting the impact of increasing frequency and intensity of hot days and heatwaves on other wildlife.