In a study published in the journal Science, researchers published new insights into the long-distance migration habits of common noctule bats (Nyctalus noctula), one of only four bat species in Europe known for their extensive migrations. The study, led by biologist Dr. Edward Hurme at the Max Planck Institute for Animal Behavior, revealed that these bats harness warm storm fronts to conserve energy during their lengthy journeys.
Over three spring seasons, the research team marked 71 female common noctule bats with ultra-light intelligent transmitters weighing only one gram—approximately five percent of the bats' total body weight—using temporary surgical glue. These transmitters, developed by scientists at the Max Planck Institute, allowed the researchers to track the bats' movements and collect data on environmental conditions. According to Agencia SINC, the sensors registered over 1,400 measurements daily, including the bats' activity levels and environmental data such as temperature, air pressure, and wind speed, providing an unprecedented level of detail about the bats' migration patterns.
The findings showed that the tagged bats traveled up to 1,116 kilometers in 46 days, with single-night flights reaching approximately 400 kilometers after evening foraging. As reported by Spektrum der Wissenschaft, the bats generally flew northeast at speeds of about 13 to 14 meters per second, challenging previous assumptions about their migratory capabilities. The migration routes were more diverse than previously thought, with bats moving throughout the landscape without a single migratory corridor.
A behavior pattern observed was that, at certain times, many bats would suddenly set off on long-distance flights—a phenomenon explained by meteorological changes. Researchers detected a surprising pattern: "On certain nights, we saw an explosion of departures that looked like fireworks of bats," said Edward Hurme, according to Agencia SINC. Further analysis revealed that the bats behaved like surfers, using warm storm fronts to fly with less energy expenditure.
According to NPR, the bats timed their springtime departure to coincide with warm fronts that precede storms. These winds tend to blow in the general northeasterly direction of the bats' migration, giving them a lift. "We found that a lot of bats are actually migrating before storms come through," said Hurme. "They were riding storm fronts, using the support of warm tailwinds," he added, according to discoverwildlife.com.
Unlike birds, which often fly thousands of kilometers without pause, bats alternate their migratory flights with frequent stops, likely due to their need to feed continuously. "Unlike migratory birds, bats don’t gain weight in preparation for migration. They need to refuel every night, so their migration has a hopping pattern rather than a straight shot," explained Dina Dechmann, according to Nauka w Polsce. This behavior underscores the challenges bats face during migration and their reliance on favorable environmental conditions.
By integrating weather data, including wind speed, wind direction, and temperature, the researchers determined how environmental conditions affected migration timing. They found that bats migrate during higher temperature peaks with lower air pressure at their departure location. As reported by Agencia SINC, this suggests that absolute temperature is a trigger for many bats to migrate. The ability to harness storm winds and warm air currents allows the bats to conserve energy, which is particularly important given the challenges they face during migration.
Waiting too long to migrate can cause bats to expend more energy, especially if they miss seasonal storm fronts. For pregnant female bats, delaying departure means carrying a heavier baby belly, adding to the challenges they face during migration. Collisions with wind turbines kill many bats, and migrating bats are threatened by various forms of human activity.
One result of the study could be a change in practice at wind farms, including turning off turbines at night when bats are flying and during periods when squadrons of migrating bats are likely passing through an area just before a storm. "Understanding when and where bats migrate could help researchers construct bat migration forecasts," reported NPR.
"We have a long way to go, but hopefully we can start moving towards a better system of being able to predict exactly when and where bats should be migrating," added Hurme.
The article was written with the assistance of a news analysis system.