Soaring temperatures sent more than 5,000 dead bats falling to the ground in New South Wales, Australia.
Flying fox bat carcasses littered streets in the town of Casino after the temperature hit 44 degrees Celsius.
Some residents mounted a last-ditch effort to save the remaining bats by hosing them down with water.
A clear-up operation has been launched to remove the decomposing remains by the local council before the stench becomes over-powering.
Photographer Dee Hartin captured the mass deaths. She told Huffington Post UK: "What I saw when I got there was beyond belief. There were hundreds of them all over the ground everywhere I looked.
"They were not only on the ground dead but hanging in the trees dead as well. I saw many young ones around three-four months old clinging to their dead mothers or hanging in the trees next to them.
"It was a horrific sight and I was distressed to see such a massive loss of life."
Almost 100 orphaned baby bats aged between two and four weeks have so far been found, with some still suckling at their dead mothers. Many of the pups are being cared for by Wires animal rescue service.
"Extreme heat caused the death of thousands of Flying Foxes in the Casino camp," Wires said in a statement.
"Thousands of Flying Foxes died, dropping to the ground, killed by the extreme heat, low humidity, and lack of shade. Female Flying Foxes have young this time of the year and hundreds of babies were clinging to their dead mothers on the ground.
"Each of these orphans had to be assessed, hydrated and taken care of individually; you can imagine the enormous task of literally hundreds coming in at the same time," said Wires.
Wildlife careers are now working around the clock to try to save them, with hundreds more are expected to be brought in. Authorities are urging people to leave the rescue mission to trained professionals due to risk of infection from bites or scratches.
Richmond Valley Council manager John Walker said: "Some areas along the riverbank are inaccessible and the stench from the rotting carcasses will be quite unbearable for some time yet.
"People should avoid the area and not try to help living bats themselves as they could bite and scratch and some carry the lyssavirus."
Bat Conservation and Rescue Society president Katrina Faulkes-Leng told the Courier Mail that bats are badly affected by extreme heat: "Once it hits a certain temperature inside the colony, bats start to suffer heat stress. If we can get into colonies then and spray with water, we can stop the stress becoming heat stroke, which kills them.
"That's what happened to the colonies that crashed — it went beyond the point where we could save them. So we can only take off the live young that are still attached to their mothers on the ground."
Now there are fears the dead bats could spread diseases and spark a public emergency. Bats have been blamed in other countries for spreading conditions such as Ebola and even HIV.
Casino official John Walker told the Australia Telegraph: "People should avoid the area and not try to help living bats themselves as they could bite and scratch and some carry the lyssavirus.
"Some areas along the riverbank are inaccessible and the stench from the rotting carcasses will be quite unbearable for some time yet."
The incident in Casino is just the latest example of bats dying in huge numbers due to Australia's hot weather. In January, 100,000 of them fell from the sky in Queensland.