First published on the National Wildlife Federation blog January 16, 2014

Images of Australian baby bats in rehabilitation, bundled up in colorful blankets and being bottle-fed are now a common sight on the Internet as heat waves become more frequent Down Under. Australia is home to four species of flying fox, some of the world’s largest fruit eating mega bats. These mega bats play a vital role in the regeneration of Australia’s forests, pollinating and dispersing the seeds of numerous native plant species.

Record high temperatures of 109F or more last week however have devastated these flying fox colonies with estimates of up to 100,000 bats killed in the heat. As the soaring temperatures continue, bat rehabilitators are struggling to cope with influx of hundreds of dehydrated and heat stressed animals as they fall from the trees all over southeastern Queensland. This however is not an isolated incident, with similar events having occurred across the country in past summers with increasing frequency over the last decade.

Why are flying foxes dying?

Although adapted to the warm Australian climate, these large mega bats have trouble regulating their body temperature when mercury starts to rise above 104F.

To help combat this, flying fox colonies naturally take up roost in trees close by rivers and water bodies, where they can access water for drinking and drenching their fur to help cool them down.  However habitat loss and urban encroachment has restricted the number suitable roost sites near water, forcing many colonies to take up roost in areas with little water close by.

Several of the flying fox species also give birth and nurse their young over the summer months. Nursing mothers naturally have an elevated body temperature at this time and have greater difficulty keeping cool when the environment heats up. Because of this, the vast majority of female bats that die from the heat are mothers with dependent young. Flying fox pups are generally less able to regulate their body temperature than adults and thus too are at high risk from extreme heat. If they don’t first die from the high temperatures, they often succumb to dehydration and starvation once they have lost their mothers.

Could this be linked to Climate Change?

Between 1994 and 2008, more than 30,000 flying foxes died in colonies across Australia from heat stress in 18 separate extreme heat events. Since then we have seen larger and seemingly more frequent fatal heat events, with 15,000 flying foxes dying in Sydney alone in 2013 and up to 100,000 across Australia in the last few days.  Climate models predict that these extreme heat events are likely to increase in frequency, intensity and duration in the coming years.

This is of great concern to scientists not only due to the increased risk of these “die off” events, but also for the long term impact it will have on the recovery of several of these already threatened species. The Grey-headed Flying fox was once considered an abundant species with numbers estimated in the many millions. Now less than 400 000 remain. As these flying foxes only have one pup a year, the loss of these mothers and pups due to extreme heat events poses a real risk to the survival of this vulnerable species and the important ecosystem services its provides.

But the bats are not alone in coping with the heat—thanks to dedicated groups like Bat Conservation and Rescue QLD who have rescued many flying foxes and will continue to help future injured wildlife. This issue just stresses the importance of taking action both on the ground for wildlife and with legislation that mitigates our impact.