The secret behind the elephant’s trunk

If no one had ever seen an elephant and by chance the skull of an elephant appeared, scientists would probably not be able to deduce the existence of the most characteristic anatomical feature of this animal: the trunk. The facial appendage is to the elephant what the long neck is to the giraffe, its hallmark. And how he uses it to do different tasks, from ripping tree trunks apart to gently uprooting the most fragile vegetation, is a sight in itself.

How does the elephant manage to carry out such versatile jobs with its trunk?

A new study from the Georgia Institute of Technology (USA) suggests that these animals not only use their muscles to stretch their trunks, but the skins on their skin also play an important role. The article is published this week in the scientific journal ‘Proceedings of the National Academy of Sciences’ (PNAS).

Andrew Schulz, lead author of the study, and his team filmed two African savanna elephants foraging for bran and apples at Zoo Atlanta. “When people extend their tongue, a muscle-filled boneless tissue similar in composition to an elephant’s trunk, stretches evenly. We expected the same when we challenged an elephant to find food.”Schulz says.

However, things did not work out that way. “When we looked at the images from our high-speed camera and traced the movements of the tube, we were surprised. The top and bottom were not the same at all.”Schulz points out.

After watching the video, the researcher stretched tissue from a stuffed elephant to better understand skin elasticity. It was then that he discovered that the skin does not stretch evenly. The upper part of the tube is 15% more flexible than the lower part. And that asymmetric stretching is due in part to differences in the skin’s wrinkle patterns. When reaching for food or objects, the dorsal section of the trunk slides further forward.

«The flexible folds of the skin are the innovation of the elephant»says David Hu, an adviser to Schulz and a professor at the Woodruff School and the School of Biological Sciences. “They protect the dorsal section and make it easier for the elephant to bend down, the most common grip style when picking up objects”.

like an umbrella

The study also found that an elephant’s trunk differs from other boneless, muscle-filled appendages found in nature, such as the tentacles of squids and octopuses. Instead of spreading out evenly, an elephant telescopes its trunk like an umbrella, gradually lengthening in waves.

An elephant first extends the section that includes the tip of its trunk, then the adjacent section, and so on, gradually moving back toward its body. For Schulz, the progressive movement towards the base is intentional.

“Elephants are like people: they are lazy”He says. “The section at the end of the tube is 1 liter of muscle. The section closest to the mouth has 11 to 15 liters of muscle. An elephant will first stretch the end of the trunk and then the adjacent section, because they are easier to move. If an elephant doesn’t have to work very hard to reach something, he won’t.”.

As a mechanical engineer, Schulz also sees applications for these findings in robotics, which today are typically built for high strength or high flexibility. Unlike an elephant’s trunk, machines can’t do both. “Soft robotics created with bio-inspired design is always based on muscle movement. If they were wrapped in a protective skin, like an elephant’s muscled trunk, the machines could apply greater forces.”he assures.

Font: JUDITH DE JORGE / ABC

Reference article: https://www.abc.es/ciencia/secreto-trompa-elefante-20220719133021-nt.html