Thousands of heat-stressed bats are dropping from trees and creating a health hazard in far north Queensland, as a record-breaking heatwave blasts the region.
About 3500 flying foxes are estimated to have perished since the furnace-like conditions began on Sunday.
However, Trish Wimberley of the Australian Bat Clinic says that's a conservative estimate, with thousands more likely to perish before the heatwave ends.
"When you have temperatures 40 degrees and over, especially for the consecutive days, you will start losing bats," she told AAP on Wednesday.
"They can't sustain an internal temperature over 40 degrees exactly like humans can't - they just drop out of the trees dead and dying."
Ms Wimberley said one Cairns bat colony sustained an 80 per cent death toll and four others had also "crashed".
Volunteers picked up 1000 dead bats at the colony but managed to save about 300, she said.
Colonies at Townsville and Ingham have also crashed, Ms Wimberley said.
"All (volunteers are) seeing is hundreds and hundreds of dead bats of a species that is critically endangered, it's heartbreaking."
Ms Wimberley said during an extreme heat event in 2010, 50,000 flying foxes died in just two days.
Health authorities have warned residents not to handle the bats after a spike in bites and scratches.
About 15 per cent of the bat population carries the potentially deadly Australian bat lyssavirus.
"ABLV is an infection like rabies, which can be transmitted through a bat bite or scratch, or possibly through exposure of the eyes, nose or mouth to bat saliva," Doctor Richard Gair, director of Tropical Public Health Services said.
Dead or distressed bats will be collected by trained wildlife workers.
