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Pachyderm propulsion surprises scientists

thailand2006-mocap-elephant5.jpgElephants move differently to all other quadruped animals, with all four limbs being used for both braking and propulsion.

Other four-legged animals use their rear legs for propulsion and their front legs for braking. Elephants, by contrast, have adopted a “four wheel drive” approach, says John Hutchinson, of the Royal Veterinary College in London.

“We have developed some new techniques for looking at animal movement that may change the way that we view the locomotion of other animals. Regardless, we have shown that elephant legs function in very strange and probably unique ways,” says Hutchinson (press release).

“We even overturned some of our own previous ideas about elephants, which is always initially disheartening but ultimately exhilarating for a scientist.”

Hutchinson has previously used his pachyderm platform to see whether elephants can actually run, concluding that at high speeds their front legs may walk but their back legs trot.

Now, using a combination of special platform to measure the force exerted by six pachyderms running and high speed video cameras to watch them doing the running, Hutchinson and colleagues monitored movement and worked out the ‘effective mechanical advantage’ of elephants at different speeds (EMA). EMA is basically the leverage of each limb and large animals increase their EMA by straightening their limbs.

Hutchinson found that elephant EMA was only a third of the expected value, and it decreased sharply as they increased their speed. This means their limbs have less leverage, especially at high speeds, and makes running less efficient.

“Thus, their locomotor repertoire is broader than might be expected from conventional hypotheses regarding size-related constraints,” the authors write in PNAS. “This increases the possibility that other giant tetrapods, such as sauropod dinosaurs, likewise might have been more than stiff-legged walkers, or that locomotor diversity in the past might have been greater than the present might suggest.”

Stately sauropods galumphing like elephants? Someone needs to update Jurassic Park…

Image: elephant with painted on spots to assist motion capture / RVC


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