By: Annie Huang

On a sunny day at the Atlanta Zoo in Georgia in 2020, an African bush elephant named Kelly reached out for a snack. However, her actions revealed something strange. The skin on top of her trunk stretched more than the skin underneath. High-speed cameras caught this on video. Andrew Schulz, a mechanical engineer at Georgia Tech in Atlanta told reporters, “But that didn’t make any sense.”

This was not the first time people made some findings about trunks, such as how elephants use them to move air, liquids, as well as solid objects. Therefore, scientists had to do further investigating to figure out. They had assumed that the skin on elephant trunks largely stretch the same way all over.

Schulz gathered up data about a male elephant, Msholo. He sent them to colleagues and asked them for a second opinion about the data. “Oh yeah, your data is wrong,” he remembers them saying. But follow-up experiments would show otherwise.

Studies involved stretching pieces of elephant skin in the lab, and they also showed the same strange phenomenon. The skin on the top and bottom of the trunk were totally different. “Talk about a great day as a scientist! That’s when we really started to believe that what we were saying was true,” Schulz said.

Scientists discovered that the tough upper skin on an elephant’s trunk crumples into creases like the folded skin of a shar pei puppy. However, the skin on the underside is only lightly wrinkled. The team shared its findings on August 2nd in the Proceedings of the National Academy of Sciences. Schulz and his colleagues have found that the bunched upper skin is about 15 percent stretchier than the lower bottom parts of the skin.

The team also observed that the trunk extends like a telescope so the tip stretches out first, followed later by the sections closer to the elephant’s head.

Scientists have studied elephant trunks for a long time. The skin on those trunks has largely been overlooked, Lucia Beccai says, a soft-robot developer who works at the Italian Institute of Technology in Genoa. She wasn’t involved in the elephant research; however she is interested in using knowledge about animals to build better robots. Artificial skin is often modeled after human skin, Beccai says. Researchers could learn a lot from other animals, though. Understanding how Kelly’s and Msholo’s folds and wrinkles stretch is “surely information that will improve the design of soft robots,” she says.

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