Science! How the elephant got its wrinkles: A look at Elephant Trunks

If you've ever wondered how an elephant's trunk works, now you'll know and it has to do with the wrinkles- thanks to this latest research.

(photo: The wrinkles that allow elephants to flex their trunks appear both before birth and with repeated use.Lena V. Kaufmann) 

How the elephant got its wrinkles

Origin of the famed creases reveals how the trunk became the “most unbelievable grasping organ on the planet”

8 Oct 2024 By Sara Reardon, SCIENCE Magazine

An elephant’s trunk is so much more than a nose. The pachyderms use their prehensile probosces to pick up food, spray water or sand across their backs to cool off, and trumpet warnings to other elephants. Baby elephants even employ their trunks to nurse, sucking up milk and then spraying it into their mouths. “It’s the most unbelievable grasping organ on the planet,” says computational neuroscientist Michael Brecht of the Humboldt University of Berlin.

But why does the trunk —a muscular appendage without any bones —work so well? One key is an elephant’s famed wrinkles, which—on the trunk—act like hands and elbows, Brecht and colleagues report today in Royal Society Open Science. The team also discovered where these wrinkles come from in the first place—and how they help make trunks so versatile.

Elephants are Born with Wrinkled Trunks

When Andrew Schulz, a mechanical engineer and biophysicist at the Max Planck Institute for Intelligent Systems, started to look at elephant trunks, he assumed their characteristic wrinkles developed over time as the animals used them repeatedly—much like smile lines that form in human faces. But he soon realized that even newborn elephants have wrinkly trunks.

Many baby animals—including humans—are born with random wrinkles because they have too much skin for their body shapes. Baby elephants’ trunk creases, by contrast, are consistently in the same places and form before birth, suggesting they have a specific purpose. “We think these wrinkles are very underrated,” Brecht says. To learn more, Schulz, Brecht, and their colleagues turned to two elephant species, Asian elephants (Elephas maximus) and African elephants (Loxodonta africana), which are known to use their trunks in different ways. 

Difference in Trunks of African and Asian Elephants

African elephants have two tough cartilage “fingers” at the ends of their trunks that allow them to pinch objects. 

Asian elephants, by contrast, have one finger and one bulbous projection that they use to clamp large objects such as melons between their trunks and lower lips.

The researchers examined differences between the species in museum specimens, zoo animals, and photos. Asian elephant trunks, they found, contain more wrinkles: 126 of them, on average, compared with the 83 of African elephants. The extra creases might give the Asian species more flexibility to make up for not having an extra “finger,” Schulz says. In both species, the wrinkles were concentrated at a pivot point, which works like a muscular elbow to allow the trunk to wrap around objects.

To study how these wrinkles form, the team gathered two Asian and three African elephant fetuses in museum collections, along with dozens of published photographs or drawings of fetuses at different ages. By lining these up sequentially, the researchers were able to form a visual timeline of prenatal trunk development. Wrinkles, they found, begin to appear as soon as the trunk does—about 20 days into the elephant’s 22-month gestation. Over the next 150 days, the number of wrinkles increases exponentially in both species, doubling every 3 weeks, and concentrates around the pivot point. Asian elephants acquire even more wrinkles later on in development.

The scientists next looked at whether trunk use contributes to additional wrinkle formation, as they originally suspected. Elephants are either left- or right-trunked, meaning they consistently bend the appendage to one side to put food in that side of the mouth. Over time, the researchers found, this bending creates more wrinkles on one side than the other.

Schulz hopes the research will inform work on soft robots used in disaster response. These robots’ joints are controlled by moving hydrostatic pressure around, much like elephant trunks, and their flexible bodies allow them to sneak into small spaces.

Elephants are the ideal model for studying soft joints, Hutchinson says. Although other animals such as primates and elephant seals can inflate organs by pumping blood into them, none of them have the specialized joints and dexterity of elephant trunks. “Elephants are doing their own thing,” he says.