Although scientists knew that some bats could reach heights of over 1,600 meters (or approximately one mile) above the ground during flight, they didn’t understand how they managed to do it without the benefit of thermals that aren’t typically available to them during their nighttime forays. Now, researchers reporting in the journal Current Biology on February 4th have uncovered the bats’ secret to high-flying.
It turns out that the European free-tailed bats they studied — powerful fliers that the researchers documented sometimes reaching speeds of up to 135 kilometers (84 miles) per hour in self-powered flight — do depend on orographic uplift that happens when air is pushed up over rising terrain to help them fly high, just as birds do during the day. But, because that’s harder to find during the cooler night, they have to rely on just the right sort of areas to reach those high altitudes.
“We show that wind and topography can predict areas of the landscape able to support high-altitude ascents, and that bats use these locations to reach high altitudes while reducing airspeeds,” explains Teague O’Mara, of Southeastern Louisiana University and the Max Planck Institute of Animal Behavior. “Bats then integrate wind conditions to guide high-altitude ascents, deftly exploiting vertical wind energy in the nocturnal landscape.”
To make these discoveries, O’Mara and colleagues fitted the free-tailed bats with high-resolution GPS loggers that recorded their location in three-dimensional space every 30 seconds, tracking them for up to three days during the approximately six-hour night. The data show that bats emerge just after sunset and fly constantly throughout the night before returning to roost.