PARIS, Nov 28: Scorching heatwaves linked to climate change have caused thousands of Australian bats to drop dead after flapping their wings in a desperate bid to cool off, according to a study published Wednesday.

On one day alone in 2002, up to six percent of the flying foxes in a nine colonies in New South Wales died when temperatures hit 42 degrees Celsius, according to the study.

Most alarming, said the biologists, was the mortality rate among young bats, as high as 50 per cent.

“The effects of temperature extremes on flying foxes highlight complex implications of climate change for behaviour, demography and species survival,” says the study, published by the Royal Society, Britain’s de-facto academy of sciences.

The fruit-eating, winged mammals play a critical role in local ecosystems, helping to pollinate wild and cultivated crops and disperse seeds, the researchers point out. Besides an increase in extreme weather, flying foxes, are also threatened by human encroachment of their habitat. They are often killed outright as pests.

The two species most affected by heatwaves, Pteropus alecto and Pteropus poliocephalus, are listed as “vulnerable” on the New South Wales Threatened Species Conservation Act, adopted in 1995.

The UN’s climate change panel said in an authoritative report on global warming this year that rising average temperatures have already begun to provoke more intense and more frequent heatwaves.

Humans are subject to the effects of such extremes as well: 15,000 deaths were attributed to a month-long hot spell in 2003 in France alone, the panel said.

On January 12, 2002, in the middle of the Australian summer, the scientists observed how the bats — hanging from exposed canopy trees — reacted to the heat.

First the animals sought shade and began “wing fanning” to cool themselves, they reported. Within a couple of hours the flying foxes were panting, and soon they were drooling saliva.

Finally, “individuals began falling from the trees ... and died within 10-20 minutes,” the study found. The researchers estimate that over 30,000 flying foxes have died due to heatwaves since 1994 during 19 similar events.—AFP