A student holds a hoary bat she found injured in Pincher Creek's turbine fields. ((CBC))

Alberta researchers have found a simple way to drastically reduce bat deaths at a wind farm in Pincher Creek.

Slowing the speed of the turbines at night during peak bat migratory periods reduces fatalities by 60 per cent, according to a joint study by the University of Calgary and power company TransAlta published in the Journal of Wildlife Management.

The researchers looked at the Summerview Wind Farm near Pincher Creek, where 500 to 600 bats die every year, compared with the 30 bats usually killed annually at wind farms in the province.

Robert Barclay, a professor of biological sciences at the University of Calgary, said the bats died after hitting turbines that could spin as fast as 200 kms an hour.

The air conditions created by those spinning blades also killed the bats, he said.

"They get caught in the low pressure area around the blade and it causes damage to their lungs and they die as a consequence of that."

The condition, known as barotrauma, affects bats more than birds because bat lungs are balloon-like and can over-expand, bursting surrounding capillaries.

Experiment during migration season

As an experiment, TransAlta slowed the blades down at night during the bat's peak migratory season, from August to September, and found it reduced bat deaths by 60 per cent. Fewer bats hit the blades and the slower speed reduced the intensity of the low pressure pockets, causing fewer lung collapse.

TransAlta is making the change permanent, said spokesman Jason Edworthy.

"We're now moving to that being the new operational mode," he said.

The University of Calgary researchers will now continue their work on finding out what is attracting the bats to the turbines in the first place in the hope of reducing the mortality rate even further.

Preserving the bat population is crucial because a single bat can eat thousands of insects a night, said Barclay.

"Pest species of crops and forests for example. Species of insects that directly influence humans [such as] mosquitoes and other biting sorts of flies."