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When Asian elephants feel the need for speed, they do not just walk fast. They do something else that defies easy description.

“It is certainly more than just walking,” says John Hutchinson of Stanford University in California. “It may be running, but I want to be cautious.”

To study the fast motion of elephants, Hutchinson and his colleagues in the US and Thailand performed intricate biomechanical video analysis of Asian elephants. The work may overturn the long held belief that elephants do not run, and could also give insights into the movements of other large animals, including dinosaurs.

Robert Full, of University of California, Berkeley, says the work is important. “We know very little about the biomechanics of large animals,” he says. “Here’s a hint there’s definitely something unusual going on. I can’t wait to see the next study.”

Hutchinson believes the work may even be useful in the clinic one day. For their size, elephants have fairly small muscles, he says, which would make them analogous to an obese humans or people with weak or paralysed muscles. “Understanding how elephants move so quickly could lead to new strategies to help some patients exercise or move about,” he says.

Going aerial

When many quadrupeds reach their top speed, all their limbs leave the ground during part of their gait. So one definition of the transition between walking and running is when the footfall pattern becomes partially “aerial”. A biomechanical definition of running requires a gait where the centre of gravity of an animal moves up and down in a pogo stick-like motion.

Hutchinson’s team videotaped 42 healthy, active animals whose joints had been painted with white dots, to make their movements easier to follow. To encourage the elephants acceleration, the researchers cheered the animals on, gave them food rewards, had them race their trainer or put a friendly elephant at the finish line.

You can see a pachyderm in motion here. (0.7Mb .mov file)

The results were surprising in a number of ways. The elephants’ top sustained speed of 25 kilometres per hour (16 mph) is fast enough, in theory, to launch the animals into an aerial gate. But the animals always kept three feet on the ground and used the same four-step gait as when they were walking slowly.

However video analysis of the hip joint hinted that elephants do run, in a biomechanical sense. The hind limb appeared to move downwards in the middle of the stride and then upwards, a characteristic of running. That would have settled the question, except that analysis of the shoulder spot showed it moved upwards and then downwards – the biomechanical signature of walking.

Groucho gait

While that makes an elephant gait very unusual, Hutchinson speculates that it is a variation of the “Groucho gait”, named after the crouched stride of the comic actor Groucho Marx.

Avoiding an aerial phase could be important for a large animal, says Hutchinson: “They wouldn’t have to endure the shock of leaving the ground and falling back down.”

The only definitive test is to measure the force an elephant exerts on the ground at different speeds, to directly measure the extra force a running, pogo stick-like motion should create.

Hutchinson and his colleagues are now designing an appropriate force platform. “The ones we have would break if an elephant moving at even moderate speed stepped on them,” he notes.

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