Identify a Right-Trunked Elephant from a Left-Trunked One by Examining the Wrinkles

There’s a Sherlock Holmes tale in here somewhere: A clever observer could check wrinkles and whiskers on an elephant trunk to catch a left-trunker pachyderm perp masquerading as a righty, thanks to a new study of trunk skin wrinkles.

Rather like people grabbing a pen with the preferred hand, an individual elephant tends to bend its trunk toward the left or right when curling it to scoop up a fruit or other object of desire. Trunk whiskers on the opposite side of the curl get scuffed against the ground, and so become shorter and sparser. And trunk skin gets a bit wrinklier on the curled-in side over the years as more little creases form with the bending, says mechanical engineer Andrew Schulz of the Max Planck Institute for Intelligent Systems in Stuttgart, Germany.

Clues to this trunkedness are just some of the novel details of elephant skin wrinkles Shultz and colleagues describe October 9 in Royal Society Open Science.

Elephant trunks, along with octopus arms and mammal tongues, get attention from enthusiasts of soft robots, he says. But the whole bendy, squiggly area of research also highlights how strange an elephant trunk is.

It’s more sci-fi space tentacle than just some long animal nose that bends. Trunk muscles form what a scientist would call a muscular hydrostat, a boneless tube of muscles that easily changes shape. (A trunk has some 46,000 muscles; the human body has 600 to 700.)

Yet unlike an anemone or octopus tentacle, an elephant’s thick outer skin puts limits on the trunk’s movement. Still, that skin turned out — to some people’s surprise — to be stretchier on the trunk’s upper surface than underneath (SN: 7/18/22).

With a mix of flexibility and power, an elephant can peel a banana or pick up a tortilla chip without breaking it, though not the way human fingers would (SN: 4/21/23). The chip lift, for instance, employs a sort of glob-squish suction.

Looking at preserved tissue (from deceased zoo animals), the team tracked how wrinkles start forming in utero, doubling about every 20 days during an early, rapid-wrinkle stage.  

Trunks like a lot of other mammal flesh gets wrinklier with age. For instance, newborns averaged 87, while the three older African savanna elephants (Loxodonta africana) had accumulated on average 109.

These wrinkles are not just cosmetic signs of aging; they’re features key to making an elephant an elephant. They protect that shape-shifting hydrostat of trunk, Schulz notes, and allow for shape change, especially when gripping heavy objects with the underside of the trunk.