More than 2,000 native flying foxes have perished due to heat stress in eastern Victoria after Friday’s extreme heatwave pushed temperatures into the mid-40s.

The Victorian government launched an emergency response over the weekend after dead and injured grey-headed flying fox colonies were found in Bairnsdale and Maffra in eastern Victoria.

Staff from the Department of Environment, Land, Water and Planning, Victoria police and local councils, along with wildlife officers and veterinarians, conducted emergency assessments and triage of injured and heat-stressed animals.

The department said on Monday that, despite the intervention, 1,513 flying foxes had died in a section of the Mitchell River walking track in Bairnsdale. About 30 animals had been taken into care by wildlife shelters and carers.

The figure represents more than a third of the population at the Bairnsdale site, based on the most recent count of animals in December, which recorded 4,030 individuals at that site.

The Bairnsdale grey-headed flying fox colony has been monitored since 2002, with monthly population surveys since 2008. The population peaked at 60,000 individuals in May 2014.

Numbers have fluctuated since that time and range from zero to 20,000 individuals depending on the time of year, the department said.

The department is still confirming that a further 963 flying foxes from a colony outside Maffra have perished.

“Heat stress events are natural and flying foxes have evolved to deal with temperatures in excess of 40C for short periods,” a spokeswoman said. “However, they are not equipped to deal with prolonged temperatures in excess of 40C, especially when the heat is accompanied by low humidity and hot drying winds, as was experienced on 25 January.”



She said the department would continue to monitor both sites over the coming days.

DELWP spokesman Peter Simpson told the ABC on Monday the deaths were unprecedented in eastern Victoria.

The mass deaths follow a similar event in Queensland in November, where an extreme heatwave caused the deaths of thousands of spectacled flying foxes.

Evan Quartermain, head of programs at Humane Society International – which has been pushing for increased protections for native flying fox species – said deaths of animals in Victoria were “disturbing”.

“That thousands of grey-headed flying foxes are dying so horrifically at the southernmost point of their range is extremely disturbing, especially so soon after spectacled flying foxes met the same fate in Cairns late last year,” he said.

“It’s becoming clear that nowhere is safe from the heat for Australia’s bats. Their habitat has been destroyed to the point that they simply can’t find appropriate shelter when temperatures rise.

“This agony is the result of years of government ignorance and inaction, and it’s beyond unacceptable that the flying foxes are without a recovery plan nearly 20 years after they were recognised as a threatened species.”