Deadly wind farms give bats “the bends”, study says 

Bats suffer from an airborne version of the diver’s condition known as “the bends” when they fly too near wind turbines, experts have claimed.

Concern for the welfare of the creatures has already prompted dozens of challenges to schemes in the Westcountry.

The RSPB lodged an objection against Somerset’s first multi-turbine wind farm at West Huntspill – which is was eventually dismissed by the Secretary of State but is now subject to a High Court appeal by developers Ecotricity.

The bird charity claimed it was in a “flight path” for birds and bats which could hit the rotor blades.

Now Queen’s University Belfast has unearthed another potential problem, namely that pressure from the turbine blades causes a similar condition as that experienced by divers when the surface too quickly.

Conservationists have warned that the bodies of bats are frequently seen around the bases of turbines, but it was previously assumed they had flown into the blades.

Dr Richard Holland claims that bats suffer from “barotrauma” when the approach the structures which can pop their lungs from inside their bodies.

He said energy companies should consider turning off turbines when bats are migrating.

“We know that bats must be “seeing” the turbines, but it seems that the air pressure patterns around working turbines give the bats what’s akin to the bends.

“It’s most common in migratory species, with around 300,000 bats affected every year in Europe alone. You just find bats dead at the bottom of these turbines. One option is to reduce turbine activity during times of peak migration.”

The team at Queen’s University also found that bats use polarised light to navigate as well as echo-location.

Greater mouse-eared bats were shown to react to the way the sun’s light is scattered in the atmosphere at sunset in order to calibrate their internal magnetic compass, in a study published in the journal Nature Communications.

Researchers said a huge number of animals including bees, dung beetles and fish use this system as a form of compass, but bats are the first mammals to do so. They said they remained baffled as to how bats achieve this feat.

The finding adds to a growing list of systems used by bats to navigate including echolocation or sonar, the sun, stars and the Earth’s magnetic field, as well as smells and sight.

Stefan Greif of Queen’s University, lead author of the study, said: “Every night through the spring, summer and autumn, bats leave their roosts in caves, trees and buildings to search for insect prey.

“They might range hundreds of kilometres in a night, but return to their roosts before sunrise to avoid predators. But, until now, how they achieved such feats of navigation wasn’t clear.”

“Most people are familiar with bats using echolocation to get around. But that only works up to about 50 metres (164ft), so we knew they had to be using another of their senses for longer-range navigation.”

In the experiment, scientists showed 70 adult, female mouse-eared bats one of two different types of polarisation patterns at sunset.

They then released them in Bulgaria around 20 to 25 kilometres (12-15 miles) from their home roost in the early hours of the morning, when no polarisation was visible.

The bats that had been shown a shifted pattern of polarised light headed off in a direction at right angles from those that had not.