The mystery of why 80,000 bats a year are being killed by turbines may finally have been solved.

Scientists believe that they are attracted to the red lights which shine out to prevent aircraft from hitting wind farms.

Previously it was thought that bats turn off their sonar when high up because they do not expect anything to be blocking their path.

But a new study by the Leibniz Institute for Zoo and Wildlife Research, in Berlin, Germany, found European pipistrelle bats are drawn to red lights.

Researchers say turbine operators should install on-demand lighting which only turns on if an plane approaches.

“Bats are at a higher collision risk at wind power stations during their autumn migration,” explains Oliver Lindecke, co-author of the study.

“Our study indicates that the use of red light signals could have fatal consequences for them as this appears to attract them to operating wind turbines.

“Technological solutions already available could help. Existing light signals could easily be replaced by bat friendly alternatives, or context-dependent illumination could be deployed which is only activated if planes or helicopters are approaching a wind power plant.”