The reason bats are killed by turbines: they see red

The animals are drawn to the warning lights used to keep aircraft clear of wind farms, study finds

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

Scientists believe that they are attracted to the red lights used 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, found European pipistrelle bats are drawn to red lights.

Researchers say turbine operators should install lights that only turn on if a 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 study of 29 wind farms by the University of Exeter used sniffer dogs to locate stricken bats near turbines and found 194 were killed each month.

If extrapolated to all of Britain’s wind farms, it would mean 80,000 die each year from colliding with the blades. The number increased with blade length, with some individual turbines responsible for the deaths of five bats each month. For the new experiments, researchers installed a 24ft pole near the shoreline at Pape Nature Reserve on the coastline of the Baltic Sea in Latvia, where thousands of bats migrate each summer.

A plastic board fixed to the pole was lit-up in 10-minute intervals switching between red light, white light or darkness, while ultrasonic microphones were used to record the calls of the bats to tell if they were coming near.

The pipistrelles were recorded more frequently at the site during the red light phase than during darkness.

During the white illumination phases, no increase in the number of bats passing the board was observed.

“Bats have excellent eyesight and can even detect wavelengths invisible to us,” said Christian Voigt. “Some red light sources might potentially blind and disorient them. Whether they then respond by flying towards the source of light with the highest intensity requires further research.

“It is also absolutely crucial to understand the long-term impact of increasing light pollution on populations of nocturnal animals.

“Many bat species already struggle in our current anthropogenic landscapes characterised by intensive agriculture and high densities of wind turbines.”

The research was published in the journal Ecology and Evolution.

Record numbers of pipistrelle bats came to Britain this year, including the largest roost ever seen in Britain, at Seaton Delaval Hall in Northumberland, where 61 were counted in March. But the area has many offshore wind farms, leading to fears that a number may have been harmed during migration.

80,000

The number of bats that may be killed by wind turbines every year, according to researchers’ figures