Nav: Home

How do fish & birds hang together? Researchers find the answer is a wake with purp

January 28, 2019

Fish and birds are able to move in groups, without separating or colliding, due to a newly discovered dynamic: the followers interact with the wake left behind by the leaders. The finding offers new insights into animal locomotion and points to potential ways to harness energy from natural resources, such as rivers or wind.

"Air or water flows naturally generated during flight or swimming can prevent collisions and separations, allowing even individuals with different flapping motions to travel together," explains Joel Newbolt, a doctoral candidate in New York University's Department of Physics and the lead author of the research, which appears in the Proceedings of the National Academy of Sciences. "Notably, this phenomenon allows slower followers to keep up with faster-flapping leaders by surfing on their wake."

More broadly, the study opens possibilities for better capturing natural resources to generate energy from wind and water.

"While we currently use wind and water to help meet our energy needs, our work offers new ways to more efficiently leverage them as we seek new methods for enhancing sustainable practices," observes Leif Ristroph, one of the paper's co-authors and an assistant professor in NYU's Courant Institute of Mathematical Sciences.

It's well known that animals such as fish and birds often travel in groups, but the details of these interactions in schools and flocks are not fully understood.

In order to study the effects of flapping motions and flow interactions on the movement of members in a group, the researchers conducted a series of experiments in the Courant Institute's Applied Math Lab. Here, they designed a robotic "school" of two hydrofoils, which simulate wings and fins, that flap up and down and swim forward. The flapping motion of each foil was driven by a motor, while the forward swimming motions were free and result from the pressure of the water on the foils as they flap.

The researchers, who also included Jun Zhang, a professor at the Courant Institute, NYU's Department of Physics, and NYU Shanghai, varied the speed of the flapping motions to represent faster and slower swimmers and fliers.

The process may be viewed here: https://bit.ly/2U8fGl7 (credit: video courtesy of Joel Newbolt, NYU's Courant Institute of Mathematical Sciences).

Their results showed that a pair of foils with different flapping motions, which would swim or fly at different speeds when alone, can, in fact, move together without separating or colliding due to the interaction of the follower with the wake left behind by the leader.

Specifically, the follower "surfs" in distinct ways on the wake left by the leader. If trailing behind, the follower experiences a "push" forward by this wake; if moving too fast, however, a follower is "repelled" by the leader's wake.

"These mechanisms create a few 'sweet spots' for a follower when sitting behind a leader," observes Zhang.
-end-


New York University

Related Birds Articles:

Birds become immune to influenza
An influenza infection in birds gives a good protection against other subtypes of the virus, like a natural vaccination, according to a new study.
Even non-migratory birds use a magnetic compass
Not only migratory birds use a built-in magnetic compass to navigate correctly.
When birds of a feather poop together
Algal blooms deplete oxygen in lakes, produce toxins, and end up killing aquatic life in the lake.
Birds of a feather mob together
Dive bombing a much larger bird isn't just a courageous act by often smaller bird species to keep predators at bay.
Monitoring birds by drone
Forget delivering packages or taking aerial photographs -- drones can even count small birds!
The color of birds
New research provides insight into plumage evolution.
Migrating birds speed up in spring
It turns out being the early bird really does have its advantages.
Birds on top of the world, with nowhere to go
Climate change could make much of the Arctic unsuitable for millions of migratory birds that travel north to breed each year, according to a new international study published today in Global Change Biology.
City birds again prove to be angrier than rural birds
The researchers' observations shed light on the effects of human population expansion on wildlife.
Teaching drones about the birds and the bees
Unmanned Aerial Vehicles (UAVs) of the future will be able to visually coordinate their flight and navigation just like birds and flying insects do, without needing human input, radar or even GPS satellite navigation.

Related Birds Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Setbacks
Failure can feel lonely and final. But can we learn from failure, even reframe it, to feel more like a temporary setback? This hour, TED speakers on changing a crushing defeat into a stepping stone. Guests include entrepreneur Leticia Gasca, psychology professor Alison Ledgerwood, astronomer Phil Plait, former professional athlete Charly Haversat, and UPS training manager Jon Bowers.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".