This week I am working on some fossil penguin bones from South Africa, and was reminded of the antics of Black-footed Penguins I have seen in zoos. Like most penguin species, they are surprisingly good jumpers, and this ability is subject to active research by marine biologists.If you have ever watched penguins swimming at eye level through glass walls at an aquarium, you may have noticed bubbles streaming from their feathers. It’s great fun to observe these birds zipping past like living Alka-Seltzer tablets. However, there is a point behind the bubbles, and a new study shows that releasing air at the right time helps penguins launch themselves out of the water.
Air has lower viscosity than water, so adding a layer of air around an object can help it cut through the sea more efficiently. Engineers have even applied this concept to make speedier torpedoes. Scientists studying film of diving penguins found that Emperor Penguins store air in their plumage, which gets compressed as they dive. Moving from deep water to shallow water lowers the pressure on the air, just like when one takes the cap off a bottle of soda. As the penguins near the surface, they are able to shift their feathers so as to release the air, which escapes in bubble form. This creates a smooth layer over much of the penguins plumage, which cuts down on friction and drag, allowing the penguin to build up a serious speed. An Emperor Penguin can reach velocities of up to 3 meters per second as it jumps out of the sea onto land. This may seem like fun and games, but when a bird needs to emerge from a hole in a thick sheet of ice or make it up a steep cliff, high speeds are critical. Check out some leaping penguins in action:
You can also read the original scientific article for free here.
Reference:Davenport, J., R.N. Hughes, M. Shorten and P. S. Larsen. 2011. Drag reduction by air release promotes fast ascent in jumping emperor penguins—a novel hypothesis. Marine Ecology Progress Series 430: 171-182.