Record-Breaking Number of Flying Foxes Die in Mass Mortality Event Triggered by Heat Wave in Australia

A record-breaking number of flying foxes died during Australia’s weekend heat wave, according to multiple sources.

Wildlife Information, Rescue and Education Service’s (WIRES) Storm Stanford told the Australian Broadcasting Corporation (ABC) that the animal deaths are Illawarra’s largest mass casualty event on record. Illawarra is a coastal region in New South Wales.

Five hundred flying foxes, also known as fruit bats, were found dead in Brooks Creek on Jan. 10, and 170 in Figtree, per the outlet.

Dead flying foxes are being reported across the state of New South Wales. At Wolli Creek, Stanford said, “at least 40 animals died, but a lot of that camp you can’t get to, so that’s just a sample.” More dead bats, she said, are being found at Windsor, Parramatta, Campbelltown, and other areas of the state.

The Australian government has already declared flying foxes a vulnerable species in the country because their populations are declining due to habitat loss and human interference. The recent mass mortality event is attributable to the area’s recent heat wave, during which temperatures exceeded 100°F.

Stanford noted that the animal deaths were somewhat expected because the bats lack sweat glands, which prevent them from efficiently regulating their body temperature when they become too hot.

Marcus Burgess of Brooks Creek reflected on the recent deaths in Illawarra, saying, “We previously counted 1,500 bats out there, so with this event … [it’s] potentially a third of the population that has been killed this time, unfortunately.”

WIRES has been caring for vulnerable animals by searching for sick infants. 

“There were 23 babies at the Dapto camp that evening … and a few more the next day,” volunteer Rebecca Daly said, adding that the discovery and removal of the dead bats was “distressing.”

Stanford added that the number of flying fox deaths could grow due to the heat wave affecting the animal’s food sources. The bats could also face long-term health issues that can lead to death, such as renal failure. 

A solution, Stanford suggested, is to install sprinkler systems near the affected areas. “There’s recently been some work published that has indicated that sprinklers are very functional; they reduce deaths and are worthwhile,” she said.

The Guardian reported that hundreds of flying foxes died in the heat wave, with the deceased numbering around 2,000 bats in South Australia, and more in Victoria and New South Wales. 

Tamsyn Hogarth, director of the Fly by Night bat clinic, said that volunteers have been rescuing baby bats found holding onto their dead mothers. 

“These orphans will slowly die of heat stress, starvation, or predation if they aren’t found,” she said. 

Many of the affected flying foxes were reported to be babies or mothers, which will pose a challenge for the population’s future. 

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Hogarth has an ongoing GoFundMe to support the rescue of flying bats, particularly orphaned young.

In an update on Jan. 12, she wrote, “During this heat crisis, entire colonies were left without official on-site support, and it has largely fallen to volunteers to monitor camps, respond where possible, and deal with the aftermath.”

“In some locations, conditions deteriorated rapidly, leading to mass mortality and a surge in orphaned pups as mothers succumbed to heat stress,” Hogarth added.