In a discovery that challenges what we know about animal migration, scientists have found that bats are using storm fronts as natural highways across Europe, traveling up to 400 kilometers in a single night—shattering previous distance records for the species.
The findings, published in Science, reveal how these nocturnal mammals exploit weather patterns to conserve energy during their epic journeys, using sophisticated strategies previously observed only in birds.
Lighting Up the Night Sky
Using innovative tracking technology, researchers observed what they describe as “bat fireworks”—mass departures of bats triggered by specific weather conditions. “On certain nights, we saw an explosion of departures,” explains Edward Hurme, the study’s lead author and a postdoctoral researcher at the Max Planck Institute of Animal Behavior. “We needed to figure out what all these bats were responding to on those particular nights.”
The answer lay in the weather patterns. The bats were departing just before incoming storms, taking advantage of warm tailwinds to reduce their energy expenditure during flight.
A Technological Breakthrough
The research team tracked 71 common noctule bats using ultra-lightweight sensors that communicated “like cell phones” across Europe. “The tags communicate with us from wherever the bats are because they have coverage across Europe much like a cell phone network,” explains senior author Timm Wild, who led the development of the ICARUS-TinyFoxBatt tag.
“The sensor data are amazing!” says Hurme. “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.”
Breaking Travel Records
The study revealed that these bats can cover far greater distances than previously known, with some individuals traveling nearly 400 kilometers in a single night. However, unlike birds, which can store fat for long journeys, bats need frequent refueling stops.
“Unlike migratory birds, bats don’t gain weight in preparation for migration,” explains senior author Dina Dechmann. “They need to refuel every night, so their migration has a hopping pattern rather than a straight shot.”
Surprising Route Variety
The research also revealed unexpected variability in migration routes. “There is no migration corridor,” notes Dechmann. “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.”
Conservation Implications
The findings could have significant implications for bat conservation, particularly regarding wind turbines, which pose a major threat to migrating bats. Understanding migration patterns and timing could help prevent fatal collisions.
“Before this study, we didn’t know what triggered bats to start migrating,” Hurme explains. “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.”
While this research marks a significant breakthrough, scientists estimate they’ve only observed a portion of the bats’ total migration, which may span around 1,600 kilometers. “We are still far from observing the complete yearly cycle of long-distance bat migration,” notes Hurme. “The behavior is still a black box, but at least we have a tool that has shed some light.”
The research was conducted by scientists at the Max Planck Institute of Animal Behavior and published in the journal Science on January 3, 2025.