Hundreds of black fruit bats are dropping dead in the Northern Territory town of Katherine, prompting an investigation by local rangers.
Authorities have urged residents not to touch the sick bats at the risk of contracting a deadly virus.
NT Parks and Wildlife ranger Stacey Kessner said staff at the popular Nitmiluk National Park have reported piles of dead bats on the ground.
Bat carcasses have also been found at schools and underneath trees in Katherine.
"We've had quite a few call-outs to come and get the bats that are not well," Ms Kessner said.
It is unclear why the bats are dying in large numbers, though Ms Kessner suspects the cause could be starvation.
"The most likely case is there's just not enough food around," she said.
"The blossoms from eucalyptus and paperbark and grevilleas are either not enough, or they haven't blossomed yet to feed the black flying foxes."
People who touch a dying fruit bat must go to hospital immediately to be vaccinated, Ms Kessner said.
"There's a risk they carry lyssavirus, and if you are bitten or scratched, you can catch the virus," she said.
Lyssavirus can cause an illness similar to rabies, which affects the central nervous system and is usually fatal.
There have been three cases in Australia since it was first identified in 1996.
All three patients died.
They include an eight-year-old boy from Queensland, an animal carer, and a woman who was bitten on the finger while trying to remove a flying fox from a child.
Symptoms in humans include headaches, fever, unusual behaviour and confusion.
Tests are underway to see if the dying bats in Katherine are carrying the virus.
Ms Kessner urged residents to contact NT Parks instead of removing the bats themselves.
