How do emperor penguins manage to reach a maximum speed approaching 20 miles an hour when swimming in Antarctic waters where they have to avoid hungry leopard seals?
The secret is in the bubbles.
Scientists Roger Hughes, John Davenport and Poul Larsen discovered that the penguins use microbubbles to reduce the same friction that bedevils submarines and torpedoes.
According to National Geographic magazine:
When an emperor penguin swims through the water, it is slowed by the friction between its body and the water, keeping its maximum speed somewhere between four and nine feet a second. But in short bursts the penguin can double or even triple its speed by releasing air from its feathers in the form of tiny bubbles. These reduce the density and viscosity of the water around the penguin’s body, cutting drag and enabling the bird to reach speeds that would otherwise be impossible.
… Emperor penguins have a dense, uniform coat of feathers … air is trapped in a fine, downy mesh and released as microbubbles so tiny that they form a lubricating coat on the feather surface.
… Last year Mitsubishi announced that it had designed an air-lubrication system for supertankers. But so far no one has designed anything that can gun past a leopard seal and launch over a wall of sea ice. That’s still proprietary technology.
More photos of the penguins and their bubble technology are in the November edition of National Geographic here.