High river flows have boosted insect breeding and now more bats are being found in the South Australian Riverland.
They are not the large fruit bats that are native to east coast Australia, but smaller insect-loving bats with a plentiful food supply.
Biologist Chris Grant explained the rise.
"Because the bats species we have around here are all insectivorous, the recent increases in insect numbers is beneficial for bats because it means at the moment they will have an abundant supply of food," he said.
"Bats like a lot of things breed in spring and if conditions are good they will breed right though spring and summer.
"A high food abundance makes it easier for the young which increases the survival rate."
He said it would be impossible to accurately count the rise in the region's bat numbers.
"The only way we can monitor bat numbers is in the case of cave-dwelling bats, but most of the bats up this way are tree-roosting or living in sheds or anywhere," he said.
"It's likely that there's been a really good breeding season for bats this year which is good because bats are one of the big parts of the ecosystem that control insect numbers, especially the insects at night."
Mr Grant said many people might not have noticed the population rise.
"They're very difficult to see and the calls of most of the species are inaudible," he said.
"They don't seem to be too choosy about what they eat - anything flying around seems to be fair game from mosquito size right up to large moths and beetles."