Heatshock

Abstract

[Extract] Justin Welbergen will never forget the day he watched hundreds of animals die. It was January zooz and he was observing a colony of flying foxes in northern New South Wales, Australia. The temperature had just peaked at 43 °C when the bats started behaving oddly. They usually just dozed or squabbled noisily in the treetops, but this day was different.

"They were really distressed," says Welbergen, who was studying the social behaviour of flying foxes for his PhD at the University of Cambridge. "They were fanning themselves and panting frantically. Some were licking their wrists to cool down. And then suddenly they began falling from the trees it was raining flying foxes. If they weren't dead when they hit the ground they died soon after. Others expired in the trees. It was gruesome."

On that single afternoon, some 2000 bats died in the colony Welbergen was studying, and thousands more perished in colonies nearby. All told, around 30,000 flying foxes have died in Australia during heatwaves since 1994, with juveniles and adult females the hardest hit (Proceedings of the Royal Society B, vol 275, p 419). Welbergen called his experience "an awful epiphany. I thought the bats could cope with the heat. I was wrong."

What Welbergen witnessed could be a harbinger of an increasingly dangerous world in which rare weather events such as heatwaves, deluges, droughts and storms become much more common. These extreme events could have a severe impact on wildlife and ecosystems, possibly even driving some species to extinction.