Flying foxes die in their thousands in worst mass-mortality event since Australia’s black summer | Wildlife

Thousands of flying foxes died in the heatwave that ravaged southeast Australia last week, the largest mass mortality event for flying foxes since the Black Summer.

Extreme temperatures led to deaths in camps in South Australia, Victoria and New South Wales. Grey-headed flying foxes, listed as vulnerable under federal environmental laws, were hardest hit.

Tamsyn Hogarth, director of Melbourne’s Fly by Night Bat Clinic, said volunteers had seen thousands of dead bats at Brimbank Park and hundreds more at Yarra Bend and Tatura camps.

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Wildlife volunteers did what they could to help, she said, rescuing dozens of babies found clinging to their dead mothers. “These orphans will slowly die from heat stress, starvation or predation if they are not found.

“We also found countless adults that couldn’t withstand the heat in areas of the colonies that were warmer – like trees with less foliage and less shade cover, and the burning clay of the river banks.”

Despite the efforts of dedicated volunteers, thousands of people died in the heat. Researchers were still counting the deaths, estimating at least 1,000 to 2,000 flying foxes had died in South Australia, thousands in Victoria and up to 1,000 in New South Wales.

“Temperatures above 42 degrees are known to cause mortality in flying foxes, sometimes on biblical scales,” said Professor Justin Welbergen, a flying fox expert at Western Sydney University.

The loss of life during last week’s heatwave was “the most significant mass mortality event” since 2019-20, he said.

More than 72,000 flying foxes died during eight separate extreme heat events during the Black Summer. In 2018, a deadly heatwave wiped out 23,000 endangered flying foxes in Queensland, a third of their population at the time.

Last week, Australia’s worst heatwave in years saw temperatures in Adelaide reach 43C on consecutive days and exceed 42C on the hottest days in Melbourne and Sydney, with suburbs and regional areas recording highs between 40C and 40C.

The heat had a dual effect, Welbergen said, putting the animals under direct stress and hindering their ability to find food, making flight more difficult and reducing the availability of nectar from eucalyptus flowers.

Mothers and puppies were most affected, making it more difficult for populations to rebound.

Dr Wayne Boardman, a wildlife veterinarian and flying fox researcher at the University of Adelaide, said the flying foxes initially showed signs of distress.

“They spread their wings, they start to come down the trees, they pant a little, some try to fly to bathe in the river.”

But above 42°C, dehydration and heatstroke make it “physiologically very difficult for animals to survive”.

Members of the public have been advised never to attempt to rescue sick, injured or orphaned bats themselves, but instead to contact their nearest wildlife organisation.

Wildlife Victoria chief executive Lisa Palma said the organization had increased its emergency response capacity to deal with a surge in cases, deploying its roving veterinary service to a nationally critically important flying fox colony.

“Heat events like this can be catastrophic for native wildlife. Unlike us, our native animals cannot escape the heat and are very vulnerable to dehydration, disorientation, burns and even blindness.”

Welbergen said fruit bats were not the only wildlife affected by the extreme heat, but their deaths were often more visible, with the animals roosting in trees in large numbers, often in urban centers.

Flying foxes are like “canaries in the coal mine,” he said, providing an indication of what is happening to other animals as global warming increases the frequency and intensity of hot days and heat waves.

The work of rescuing and caring for wildlife affected by extreme weather has placed a heavy burden on volunteers and an underfunded veterinary sector, without a national wildlife rescue strategy. “We were hit with a terrible season for orphaned puppies. We were already at breaking point and dreading what the hot weather would bring – now our worst fears have come true.” Hogarth said.