PARRAMATTA'S colony of grey-headed flying foxes was depleted by the extreme January heat, with rescued pups now in the care of WIRES volunteers.
The volunteers saw the animals drop to the ground from trees at Parramatta Park, suffering heat exhaustion and severe dehydration, on January 18, when temperatures hit 46 degrees.
Adult flying foxes had scooped water from nearby ponds and tried to drip water into the mouths of their young in an effort to save their lives.
About 2000 of the flying foxes died in Parramatta and other Sydney suburbs.
Volunteer Storm Stanford said about 99 per cent of the animals that died were juveniles.
"We're losing a significant proportion of the next breeding generation," he said.
Last month 520 flying foxes were rescued in NSW.
Only 18 were rescued over the same period last year.