Unsteady Feet : To keep an elephant off balance, bring out an enormous blindfold.

For a 7,600-pound Asian elephant, putting one foot in front of the other can be a high-stakes proposition. A tumble can result in grievous injury. '' The bigger you are, the harder you fall,'' said John Hutchinson, with the Royal Veterinary College in Britain.

But scientists knew little about how elephants maintain their stability as they lumber along. A new study suggests that visual feedback helps elephants time their strides.

All it took were trained animals, a set of blindfolds and a willingness to nudge one of the planet's largest land mammals ever so slightly off balance.

[ The elephants, guided by their handlers, had zero risk of actually falling, said Dr.Hutchinson, a co-author of the study.]

Studies have shown that visual feedback helps humans fine-tune their steps. 

But it was not clear whether the same principle would be true for elephants. To test the importance of vision, the scientists investigated what happened when when they took it away.

Dr. Hutchinson and his colleague Max Kurz, a neuroscientist in Nebraska, set off to a California facility that trained elephants for movies, commercials and other types of entertainment.

The scientists attached a GPS tracker to each of four elephants' torsos and an accelerometer to the back right foot of all four elephants.

The accelerometer would produce a signal each time a foot hit the ground, allowing the researchers to track the time of a single stride.

When the elephants could see, the time of their strides was relatively consistent. But the blindfolds seemed to make the timings of their strides more erratic. 

The finding suggested that when the elephants could not see, they had more trouble calibrating the timing of their steps. [ Emily Anthes ]


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