Science

Penguins Rocket Through The Water Aboard Supercavitating Bubble Jets

Turns out not being eaten by a leopard seal is excellent motivation. It’s what spurred penguins to develop an ingenious method of cutting down their drag by wrapping themselves in a shawl of bubbles.

When being hunted by a leopard seal in the water, penguins will attempt to escape by hurling themselves out of the water and onto land or ice. To get the necessary speed, and put some distance between itself and the pursuing seal, the penguin will emit a cloud of bubbles, like those above. This veil of air greatly diminishes the penguin’s drag and helps it rapidly accelerate — like a shot of subsurface Nitro — towards safety. Some species can launch themselves as high as 3m above the surface and land unscathed on a rocky shore.

The fascinating aspect is that the bubbles aren’t being exhaled by the penguins as previously thought; they’re being shaken free from the bird’s feathers. John Davenport, a Professor at University College Cork, along with a grad student made the surprising discovery and recently published their findings in the Marine Ecology Progress Series journal. As the BBC explains,

They raise their feathers to fill their plumage with air, then dive underwater. As the birds descend, the water pressure increases, decreasing the volume of the trapped air. At a depth of 15-20 metres, for example, the air volume has shrunk by up to 75%. The birds now depress their feathers, locking them around the new, reduced air volume.

When the need arises, penguins will simply aim for the surface and let loose the bubbles. “Because the feathers are very complex, the pores through which the air emerges are very small so the bubbles are initially tiny. They coat the outer feather surface,” said John Davenport, a Professor at University College Cork.

Militaries have been attempting to duplicate this biological process since the Soviets designed rocket torpedoes in the 1960s. Even now, the US Navy is dabbling with bubble veils for its future submarines. However, none of those systems compare the the efficiency and elegance of millions of years of evolution. [Marine Ecology Progress Series via BBC via DVice]


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