While the odd waddle of penguins may appear ungainly and often amusing, it actually helps the birds to conserve energy, according to a new study by University of Colorado at Boulder and University of California, Berkeley researchers.
The study, authored by UC Berkeley biology graduate student Timothy Griffin and CU-Boulder Associate Professor Rodger Kram (a former faculty member at UC Berkeley) showed the issue is not in penguin waddling, but in their short legs.
"In terms of walking locomotion, penguin waddling takes twice as much energy as other animals of their size," said Kram, now an associate professor in the kinesiology and applied physiology department at CU-Boulder. "Prior to our study, people assumed that penguin walking was expensive because the side-to-side waddling wasted energy, and that their muscles had to do a lot of work.
"What we found was that waddling does not require much muscular input. The real reason for their high cost of walking is their short legs."
The broader evolutionary picture, however, likely reveals the primary reason penguins became such notorious waddlers, said Kram. "They don聮t walk that much except for their migrations," he said. "Most of their lives are spent in the ocean, on the ice and (standing) in cold weather. If they had long legs, that would be good for walking but bad for swimming and standing in the cold."
A paper on the subject by Griffin and Kram is being published in the Dec. 21 issue of Nature, one of the world聮s premier weekly science journals.
Kram used the analogy of a hypothetical animal triathlon. "Penguins would be very good competitors," he said. "Their swimming is superior, they toboggan along smooth ice patches using their wings like Nordic skiers use ski poles, but they are not good walkers. Few humans triathletes are great in all three sports, so it聮s a compromise."
Kram and Griffin -- Kram聮s former graduate student at UC Berkeley -- used San Diego聮s Sea World "Penguin Encounter" exhibit to conduct their experiments on Emperor penguins. They filmed and analyzed the Emperor penguins waddling across an instrumented platform to measure the side-to-side and fore-and-aft forces the birds exerted while walking, as well as the vertical forces supporting their weight.
"Our hunch was that if penguins were trying to move forward, but were expending energy rocking side-to-side with this awkward, roly-poly, back-and-forth movement, then it聮s got to be wasted energy," said Kram. "But what we found is that they are inefficient because of their short legs and big feet, and waddling is a means to cut their losses."
According to Griffin, "Our knowledge gained from penguins provides novel insight into the gait mechanics of humans with increased lateral movements, such as pregnant women or obese individuals. This information may lead to improved understanding, evaluation and treatment of individuals with gait disabilities."
Penguin photos from a color video are available on the web at: . To obtain video footage, contact Robert Sanders in the UC Berkeley media relations office at (510) 643-6998 or Hal Parham at San Diego Sea World, (619) 226-3982.