The animals' corpses rot quickly in the heat and councils have organised collections to stop the stench.
Since Christmas, record temperatures of up to 48C have been seen across Australia, hot on the heels of the country's hottest year on record.
Louise Saunders, president of Queensland's Bat Conservation and Rescue group, said the bats cling to trees and urinate themselves before dying in a desperate bid to reduce their body temperatures.
She added: "As they succumb, they just fall in heaps at the base of trees.
"You can have 250 or more - it's like dripping chocolate - all dying at the base of trees.
"It's an enormous animal welfare concern."
The extreme heat has also killed birds and animals.
In Winton, where the song Waltzing Matilda was written, a large number of parrots, kangaroos and emus have been found dead in the parched landscape.
- UK Independent