Researchers find penguins’ waddling makes sense
Published 9:00 pm Tuesday, December 19, 2000
By MICHELLE LOCKE
Associated Press
BERKELEY, Calif. – It may not be graceful, but the penguin’s waddle makes perfect sense to scientists, who found that the bird’s side-to-side gait conserves energy.
University of California researchers found that the gait works like a pendulum, with energy stored at the end of each swing for the bird’s next step.
“Our findings indicate that walking is expensive for penguins not because of their waddling, but because they have such short legs that require their leg muscles to generate force very quickly when they walk,” said Timothy Griffin, a UC Berkeley graduate student in integrative biology.
The findings by Griffin and Rodger Kram, a former assistant professor of integrative biology at UC Berkeley now at the University of Colorado, Boulder, were reported this week in the journal Nature.
Kram and Griffin decided to study penguins because they seem to be doing everything wrong. An earlier study showed penguins were burning twice as many calories when walking as other animals of similar size.
But researchers found the problem was the penguins’ legs, not their jerky side-to-side movements. The Emperor penguins studied at San Diego’s Sea World, for instance, were at least 3 feet tall but had legs only about 10 inches long.
Penguins burn about the same amount of calories as animals with similar leg lengths, Griffin said.
The researchers coaxed penguins across a force platform – “kind of a fancy bathroom scale,” says Griffin – with bits of fish.
Using scale measurements and videos, the scientists measured the side-to-side and fore-and-aft forces the penguins exert while walking, as well as the vertical forces supporting their weight. The five penguins studied had a walking speed of about 1.5 feet per second.
The percentage of energy retained during two steps is called the recovery rate. Humans have a recovery rate of about 65 percent. The penguins studied by Griffin and Kram had an impressive recovery rate of up to 80 percent.
The findings were welcomed by Gerald Kooyman, a research professor at the Scripps Institution of Oceanography who has studied penguins for 30 years. “I think that’s a very nice explanation,” he said.
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