Bats use storm fronts for energy-efficient migration

Bats use storm fronts for energy-efficient migration
by Robert Schreiber
Berlin, Germany (SPX) Jan 06, 2025

While birds dominate the skies as long-distance travelers, some bats also undertake remarkable continental migrations spanning thousands of kilometers across North America, Europe, and Africa. However, the elusive nature of this behavior has kept it largely unexplored - until now. Researchers from the Max Planck Institute of Animal Behavior (MPI-AB) have unveiled key insights into bat migration by tracking 71 common noctule bats on their spring journeys across Europe. The study, published in Science, reveals that bats leverage warm storm fronts to conserve energy and extend their range.

"The sensor data are amazing!" said Edward Hurme, postdoctoral researcher at MPI-AB and the Cluster of Excellence Collective Behaviour at the University of Konstanz. "We don't just see the path that bats took, we also see what they experienced in the environment as they migrated. It's this context that gives us insight into the crucial decisions that bats made during their costly and dangerous journeys."

Using innovative sensor technology, the team tracked noctules over portions of their 1,600-kilometer migrations. The tracking devices, developed by MPI-AB engineers, weighed just five percent of a bat's body mass. These tiny tags recorded environmental conditions and activity levels and transmitted data via a novel long-range network similar to a cellular system. Senior author Timm Wild, who led the development of the ICARUS-TinyFoxBatt tag, explained, "The tags communicate with us from wherever the bats are because they have coverage across Europe much like a cell phone network."

The research focused on female noctules, as they are more migratory than males. Tagged bats, captured and released in Switzerland, provided data over three years. The findings revealed a surprising lack of a unified migration corridor, with bats moving across a diverse landscape in a general northeast direction. "We had assumed that bats were following a unified path, but we now see they are moving all over the landscape in a general northeast direction," said senior author Dina Dechmann.

Further analysis showed noctules breaking the species' migration distance record, covering nearly 400 kilometers in a single night. Unlike birds, which bulk up before migration, bats rely on nightly feeding stops, leading to a "hopping" migration pattern. "Unlike migratory birds, bats don't gain weight in preparation for migration," Dechmann noted. "They need to refuel every night."

A pivotal discovery emerged when researchers identified weather patterns triggering mass departures. Bats initiated migration on nights with falling air pressure and rising temperatures - conditions preceding storms. These warm tailwinds reduced the bats' energy expenditure during flight. "It was known that birds use wind support during migration, and now we see that bats do too," said Hurme.

Beyond biological insights, these findings carry significant implications for conservation. Migratory bats face threats from human activities, particularly collisions with wind turbines. Understanding the timing and routes of bat migrations could help mitigate these risks. "Before this study, we didn't know what triggered bats to start migrating," Hurme explained. "More studies like this will pave the way for a system to forecast bat migration. We can be stewards of bats, helping wind farms to turn off their turbines on nights when bats are streaming through."

This study highlights the potential for technological advancements to unravel the mysteries of bat migration and inform strategies for protecting these remarkable creatures.

Research Report:Bats surf storm fronts during spring migration