Science-- there's something for everyone

Sunday, February 14, 2010

Walk like a charging elephant

One of the things I love about science is the variety of questions it can answer. It’s really amazing how varied people’s interests are, and how creative they can be in finding answers. For example, Norman Heglund, from the Universit√© Catholique de Louvain, Belgium, wondered whether charging elephants were truly running, or just speed walking.

Walking and running are actually two very different motions. Although both gaits convert potential energy stored in tendons and muscles into kinetic energy that moves the animal forward, the two movement patterns are quite dissimilar. Running animals use the stored energy to bounce forward like a pogo stick, whereas walking animals regain that stored energy by swinging their legs like a pendulum. Think of the bouncing, flexing backbone of a running dog, versus the more level backbone of the same dog when walking. Previous experiments by John Hutchinson of the Royal Veterinary College of London, indicated that elephants do not run at higher speeds but in fact simply walk faster.

Heglund wanted to test this hypothesis. Not having access to elephants in Belgium, he traveled to the Thai Elephant Conservation Centre in Lampang, Thailand, where he and his colleagues built a giant force-measuring platform. This eight meter long racetrack was made of one meter square force plates over a reinforced concrete foundation. Thirty-four elephants of assorted ages and weights were encouraged to cross the platform at speeds ranging from strolling to racing.

So, were the elephants running or walking when reaching top speeds? A little of both, it turns out. Although the elephants’ kinetic and potential energy plots resembled those of running animals, their centers of mass remained level during the first part of the stride, but bounced during the second part. It seemed as though the elephants were running with their front legs but walking with their hind legs.

Despite this, the researchers found that elephants are highly efficient movers, using 1/3 the energy of most other animals. Elephants achieve this efficiency by having a high step frequency and maintaining at least two feet on the ground at all times, limiting the bouncing motion most animals experience at high speeds.