New study may provide clues to how birds began to fly

October 19, 2018, Lund University
ubenton's bat. Credit: Jens Rydell

For the first time, researchers have measured what is known as the ground effect of flying animals—and it turns out that they save a lot more energy by flying close to the ground than previously believed. The study from Lund University in Sweden supports one of the theories on how birds began to fly.

"Our measurements show that the ground effect saves animals twice as much as models have suggested.", says Christoffer Johansson, biologist at Lund University.

For the first time, Christoffer Johansson, together with colleagues Anders Hedenström at Lund University and Lasse Jakobsen at the University of Southern Denmark, have successfully managed to measure the ground effect when Daubenton's bats fly in a wind tunnel.

In short, the ground effect means that a , ground or water, acts as an aerodynamic mirror that increases the air pressure under the wings—it costs less to generate lift. The ground effect is achieved within one wingspan of the surface, and the effect decreases exponentially with distance to the surface. An even surface, e.g. a calm lake where bats and birds catch insects or drink while they fly, provides optimal conditions. The new study also shows that animals use even less energy if they flap their wings rather than gliding near the ground.

Although the study was performed on bats, it has implications for birds and insects. One theory of how animals developed the art of flying is that they threw themselves between branches and trees. Another theory is that flying began on the ground. By running and jumping, proto-wings could have allowed the animals to run faster and jump higher and eventually flight evolved, a theory commonly known as the "ground up" theory. The corresponding theory behind today's flying insects is that they moved on the water surface and eventually evolved wings as a means of propelling themselves across the surface.

"This is obviously speculation, but if flapping animals save more energy than we previously believed by flying close to the ground, then the ground up theory becomes more probable, i.e. that the began to fly by first running and jumping on the ground with flapping precursors to wings.", says Christoffer Johansson.

The results are published in the journal Current Biology.

Explore further: Small birds have more efficient wing strokes than bats

More information: L. Christoffer Johansson et al, Flight in Ground Effect Dramatically Reduces Aerodynamic Costs in Bats, Current Biology (2018). DOI: 10.1016/j.cub.2018.09.011

Related Stories

Small birds have more efficient wing strokes than bats

February 5, 2018

Small birds are more energy-efficient than bats when flying. Researchers previously believed this was due to air resistance created by the bats' ears. However, biologists at Lund University in Sweden have now discovered another ...

Flapping protective wings increase lift

May 29, 2012

New research from Lund University in Sweden reveals the value of carrying two layers of wings around. The researchers studied dung beetles and the way their protective forewings actually function. These wings do not only ...

Bats' flight technique could lead to better drones

May 4, 2016

Long-eared bats are assisted in flight by their ears and body, according to a study by researchers at Lund University in Sweden. The recent findings improve researchers' understanding of the bats' flying technique and could ...

Winging it: How do bats out-maneuver their prey?

July 5, 2017

Bats catch food 'on the wing' without touching the ground, but how do they do it? A new study by Per Henningsson at Lund University, Sweden is the first of its kind to analyse the aerodynamics of bats performing manoeuvers ...

Engineers study hovering bats and hummingbirds in Costa Rica

September 26, 2018

Each sunrise in Las Cruces, Costa Rica, River Ingersoll's field team trekked into the jungle to put the finishing touches on nearly invisible nets. A graduate student in the lab of David Lentink, assistant professor of mechanical ...

Recommended for you

Space-inspired speed breeding for crop improvement

November 16, 2018

Technology first used by NASA to grow plants extra-terrestrially is fast tracking improvements in a range of crops. Scientists at John Innes Centre and the University of Queensland have improved the technique, known as speed ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.