Wind power is an essential component in the fight against climate change, reducing the need for high-emission fossil fuels. But wind turbines, often placed in areas of open countryside, pose a threat to wildlife. And this threat isn’t put to bed when the lights go out – a new study highlights how bats and turbines have too much in common.
The study looked specifically at noctule bats (Nyctalus noctula) in northeast Germany, a region known for its agriculture and wind power production. Recent developments in GPS tracking technology have led to the availability of GPS devices compact enough to be fitted to small animals like the noctule bat. Wearing their GPS backpacks, the bats could be tracked and their movements understood.
A shared environment
Noctule bats make up the majority of bat deaths in Germany. By tracking the bats via their GPS backpacks, the study showed that they preferred to fly and forage in open areas above grassland and water – a characteristic trait of this open-space forager. This leaves wind turbines, often erected in areas of open grassland, dangerously placed within the bats’ foraging areas. Furthermore, the bats regularly flew at the height at which the turbines operate, putting them in danger from the rotary blades.
Females were most at risk. They had varied flight paths, and also flew for longer and travelled greater distances than the male noctules. Their varied behaviour may be due to females searching for alternative roosts, social partners and other feeding areas. Females were often seen very close to turbines, frequently foraging nearby, especially in the early summer months.
“One explanation considers the fact that bats make their homes in trees. In early summer, having just finished raising their pups, the female bats take off looking for new homes and hunting grounds. Conceivably, the bats mistake the wind farm constructions for large dead trees, ideal for serving as bat homes,” said one of the authors, Christian Voigt.
Alternatively the turbines, which are often surrounded by insects, could be a beacon of food to the female bats.
Males, on the other hand, rarely crossed or foraged near wind turbines. The researchers even found some evidence that they actively avoided them, making large detours. Although male juveniles, who have yet to establish set foraging routes, were more at risk.
“These male bats had no reason to venture out. They had already established their quarters earlier in the year,” explained Voigt.
Wind turbines pose the deadly threat of collision with their fast moving blades, but they can also disrupt habitats. If bats begin to avoid turbine sites, as seen in the male noctules in this study, there is the potential that feeding grounds can be separated from roosting sites.
Changes for wind turbines
“Wind farms already carry the green stamp of renewable energy production,” said Voigt. “As a consequence, the operators feel that they made a sufficient contribution to environmental protection.” But Voigt disagrees and believes there is still work to be done.
During the summer months, when the bats are most active, changes could be made to protect the flying mammals from harm. This could be as simple as reducing the turbine speeds or stopping them during key periods. It’s estimated that without such mitigations, every year in Germany up to 250,000 bats could die at the turbines’ blades.
Roeleke, M., Blohm, T., Kramer-Schadt, S., Yovel, Y., & Voigt, C. C. (2016). Habitat use of bats in relation to wind turbines revealed by GPS tracking. Scientific Reports, 6. 10.1038/srep28961
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