Elephants’ trunks are so wrinkly to help them stretch out and reach further – and the distribution of the wrinkles helps the animals pick up objects dexterously.
When an elephant reaches out to grasp an object with its trunk, extra wrinkles in the skin on top of the trunk allow it to stretch more than the skin of the underside. This makes the trunk curl over at the tip, which helps the animal pick up objects as small as a blade of grass. “It’s really miraculous what they’re able to do,” says at the Georgia Institute of Technology in Atlanta.
Elephants’ trunks are highly muscular and have no bones. It has long been assumed that trunk extension happens simply by virtue of the appendage elongating and its diameter shrinking, in a similar way to what happens with octopus arms, says Schulz. But trunk biomechanics haven’t previously been investigated in detail.
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His team has now studied trunk extension by coaxing two African elephants, one male and one female, to reach for treats such as apples sitting on a table in front of a barred section of their enclosure at Zoo Atlanta. The team also studied the trunk of an elephant that had previously died.
The group found that the female elephant could increase the length of her trunk by 20 per cent to reach for the treats, while the male did so by 13 per cent. In both sexes, the topside of the trunk had more wrinkles, and this meant it stretched out by about 15 per cent more than the underside, which contributed to the tip curving over.
The findings may help roboticists trying to develop machines with soft or liquid-based body parts, says Schulz. “Most hydrolic limbs are like a fluid-filled balloon – no one’s ever thinking about what’s on the outside of the balloon material,” he says. “In order to have these complex movements, you need these structures on the outside to help you internally.”
PNAS
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