How bats ride storms to migrate hundreds of miles

New tracking technology reveals how female bats conserve energy by riding storm fronts during their long spring migrations.

Millions of bats form a snake-like swarm as they emerge from Deer Cave each evening in Gunung Mulu National Park on Borneo Island. Photo by Tristan Savatier/Getty Images

By Laila Azzahra and Widya Putri

A bat no bigger than your hand embarks on an extraordinary journey each spring, traveling up to 700 miles to reach warmer birthing grounds. While scientists have long known about these migrations, they lacked insights into how these small mammals complete such arduous trips. With the help of innovative tracking technology and some surgical glue, researchers have unraveled the mystery.

The mouse-sized common noctule, a bat species found in Europe, North Africa, and Asia, exhibits remarkable migratory behavior. Female noctules, weighing only about an ounce, leave their winter roosts each spring to give birth in distant locations before returning with their pups in the fall. Males, in contrast, tend to stay close to their winter habitats.

Until recently, scientists understood the locations of these roosts and birthing grounds, particularly in Germany and Switzerland. However, details about the timing, speed, and energy-saving strategies of these migrations remained elusive.

New research from the Max Planck Institute of Animal Behavior has revealed a fascinating strategy employed by these bats. Guided by seasonal temperature changes, the noctules wait for approaching storm fronts and use the wind currents to conserve energy during their migrations.

“You would have never expected the fact that they can ride the storms,” said Dina Dechmann, a behavioral ecologist at the Max Planck Institute. “It was super-surprising for us.”

Bats are typically “flapping fliers,” meaning they rely on sustained wingbeats rather than gliding. This led scientists to believe that they couldn’t utilize environmental energy sources like wind currents. However, the study showed that pregnant female bats take advantage of storm winds, reducing the physical strain of their journey.

“This idea that they can somehow use energy from the environment to save energy during flying is quite new for bats,” Dechmann added.

To uncover these insights, researchers developed tiny, lightweight sensors weighing just one gram. These sensors were designed to measure the bats’ acceleration and ambient temperature. Using surgical glue, scientists attached the sensors to the bats, enabling them to transmit real-time data every minute through a wireless network powered by the French tech firm Sigfox.

This innovative tracking system allowed researchers to monitor the bats’ movements and correlate their migration patterns with meteorological data. The study found that the bats typically embarked on their two- to three-day journeys during storm fronts, which provided favorable winds for their northward migration to regions such as northern Germany, Poland, and the Czech Republic.

The findings, published in the journal Science, provide critical information about the habits of these elusive creatures, which could play a key role in their conservation. Bats are vital for controlling insect populations, including mosquitoes, but their numbers are under threat.

In Germany alone, an estimated 100,000 bats are killed annually by rotating wind-turbine blades. Understanding the timing and routes of bat migrations could help mitigate these deaths. For example, utility companies could temporarily shut off turbines during peak migration periods, minimizing harm to bat populations.

Winifred Frick, chief scientist at Bat Conservation International, emphasized the significance of this research. “We’ve been really limited in what we can learn about bat migration by the size of the tags that we could put on them,” she said. “This new system is pretty innovative and really opens up the ability to understand how bats are moving across the landscape.”

Fijian monkey-faced bat. Photo by Avalon/Getty Images

The insights gained from this study highlight the adaptability and resilience of bats, even as they face increasing environmental challenges. By conserving energy during migration, female bats increase their chances of successfully reaching their birthing grounds and raising their young.

Furthermore, the research underscores the importance of leveraging technology to study and protect wildlife. Small, efficient tracking devices like those used in this study could revolutionize the way scientists monitor other migratory species.

As climate change continues to alter weather patterns, understanding the relationship between bats and their environment becomes even more critical. Migratory behaviors like those observed in common noctules may shift in response to changing conditions, necessitating ongoing research and adaptive conservation strategies.

For now, the discovery that bats ride storm winds represents a significant step forward in our understanding of these remarkable creatures. By combining cutting-edge technology with ecological research, scientists are uncovering new ways to protect bats and the ecosystems they support.

The next time a spring storm rolls in, consider the tiny travelers riding the winds above—an awe-inspiring reminder of nature’s ingenuity.