Fast-moving elephants run like Groucho
Speedy Asian elephants may not look like they are running, but they can, researchers say.
The massive mammals can reach speeds of up to 25 kilometres per hour, but their four feet never leave the ground at the same time the hallmark of running.
"We do find evidence that elephants run in a sense," said John Hutchinson of Stanford University's department of mechanical engineering.
"They don't leave the ground, which is the classical definition, but they do seem to bounce, which is the biomechanical definition," he added in a statement.
Researchers had thought elephants were capable of walking, ambling or trotting, but not running.
To study the motion, Hutchinson and his colleagues videotaped 42 healthy adult elephants racing along a 30-metre track in Thailand. The study appears in Thursday's issue of the journal Nature.
Over 188 trials, the elephants generally maintained an even speed over the track. Thirty-two animals reached top speeds of over four metres per second. Of these, 20 went faster than five metres per second and three reached speeds of up to 6.8 metres per second or 25 kilometres per hour.
Biomechanics called the elephants' stiff-limbed gait "Groucho running" after the bent walking style of the cigar-smoking, mustachioed comedian Groucho Marx.
When the elephants speed up, their limbs contract and bounce back like a spring. Other animals, including running birds like chickens and emus, also have limbs that stretch without forcing all feet off the ground at once.
The researchers hope their findings will provide insights into how large animals and obese people overcome physical factors that limit their movement.
To confirm if the motion measurements fit the biomechanical definition for running, the researchers are building a prototype platform to measure the force an elephant exerts on the ground at different speeds.