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A bat with a GPS tag on its back. Photo: Teague O'Mara/Southeastern Louisiana University

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."

Go deeper

Scoop: Leaked HHS docs spotlight Biden's child migrant dilemma

A group of undocumented immigrants walk toward a Customs and Border Patrol station after being apprehended. Photo: Sergio Flores/The Washington Post via Getty Images

Fresh internal documents from the Department of Health and Human Services show how quickly the number of child migrants crossing the border is overwhelming the administration's stretched resources.

Driving the news: In the week ending March 1, the Border Patrol referred to HHS custody an average of 321 children per day, according to documents obtained by Axios. That's up from a weekly average of 203 in late January and early February — and just 47 per day during the first week of January.

Ben Geman, author of Generate
36 mins ago - Energy & Environment

Mounting emissions data paints bleak picture on Paris climate goals

Illustration: Aïda Amer/Axios

Researchers keep finding new ways to reveal that nations are together showing very few signs of getting on track to meet the Paris Agreement's goals.

One big question: That's whether a spate of recent analyses to that effect, and scientific reports coming later this year, will move the needle on meaningful new policies (not just targets).

Dion Rabouin, author of Markets
3 hours ago - Economy & Business

How the tech stock selloff is hurting average Americans

Expand chart
Data: FactSet; Chart: Axios Visuals

Investors holding the ultra-popular Nasdaq 100 and S&P 500 index funds have been hard hit over the last two weeks as tech shares have been roiled by rising U.S. Treasury yields.

Why it matters: Even though the economy is growing and many U.S. stocks are performing well, most investors are seeing their wealth decline because major indexes no longer reflect the overall economy or even a broad swath of public companies — they reflect the performance of a few of the country's biggest companies.