Bats “surf” storm fronts when they migrate every year, researchers write in a new analysis this month.
Published in Science, the study sheds light on a little-known phenomenon: the long-distance migration treks of nocturnal bats. Migratory bats’ routes, and the decisions that prompt them to undertake their journeys, have long been the stuff of scientific mystery.
To uncover more about bats’ migration decisions, researchers tracked 71 noctule bats out of an original 125 tagged bats over three years. “The common noctule … is a wide-ranging European insectivorous bat,” the study says. Female noctule bats migrate up to about 1,000 miles each spring to roost.
Researchers used a tiny tracking device that collected more than 1,400 daily sensor measurements during the bats’ spring migration, offering unprecedented insight into the bats’ behavior. The researchers used the remote tags and other data to assess each bat’s locations, daily body acceleration, daily activity and other behavior information, along with data on environmental conditions such as temperature and wind. They found that changes in temperature had a strong association with migratory flight, with the bats likelier to migrate before coming warm fronts. The study also revealed that noctule bats travel farther than expected on migratory nights: up to 238 miles each a night, much farther than previous estimates.
The bats tend to migrate before storm fronts, researchers write, taking flight on nights with more wind and “surfing” the air movements that accompany changes in temperature, dropping barometric pressure and better wind to time their migrations.
The researchers found that the bats were able to migrate under less ideal conditions, too, but that migrating on colder nights with less wind support forced the bats to expend more energy.
Better sensors mean more insight into bats’ once-elusive habits, the researchers say.
“We are still far from observing the complete yearly cycle of long-distance bat migration,” Edward Hurme, a postdoctoral researcher at the Max Planck Institute of Animal Behavior and the University of Konstanz and the study’s first author, said in a news release. “The behavior is still a black box, but at least we have a tool that has shed some light.”