The bat that can surf winds a mile high

European free-tailed bats can surf uplifting winds to fly a mile high.

Why it matters: The small mammals can achieve such heights — and high speeds sometimes of up to 84 mph — without expending a large amount of energy. Harnessing those principles could help to improve drones and other high-speed, low-energy modes of flight.

Background: Researchers had detected bats high in the sky before, but it wasn't clear to them how the bats managed to fly there.

• Unlike herons or eagles whose wings structure allows them to soar, bats' hands — with skin stretched out over their fingers — are their wings, says Teague O'Mara, who studies bats at Southeastern Louisiana University.

What they found: O'Mara and his colleagues put GPS trackers on the backs of eight European free-tailed bats (Tadarida teniotis) to track their location. They then combined that data with topography, wind and weather models to see when and where the bats were flying with and against the wind.

• If wind is traveling across a landscape and hits a mountain or hill, it pushes the wind straight up.
• They saw that the bats were able to repeatedly find and ride those winds, sometimes nearly a mile up in just 20 minutes. The bats would then descend and rise again on a rollercoaster-like path, the researchers report today in the journal Current Biology.
• "That’s super incredible," says O'Mara, in part because they don't have the long-distance visibility that birds flying during the day do and instead navigate mainly on echolocation, which has a range of about 50 meters (164 feet).
• The findings suggest the bats have some type of mental map of the terrain, says O'Mara.
• How bats create that map is an open question.

The big picture: "There are so many different ways animals fly that we are still discovering parts about it," says O'Mara. "Things that we thought weren't possible appear in our faces. There is such an enormous amount of variation in life."