Scientific American - USA (2012-12)

ADVANCES

18 Scientific American, December 2021 Illustrations by Brown Bird Design

Source:

“Elephants Evolved Strategies Reducing the Biomechanical Complexity of Their Trunk,”

by

Paule Dagenais

et^ al., in

Current Biology,

Vol. 31; November 8, 2021

Six Kinematic Strategies Used by Elephants

Suction Oblique Distal Wrap

Vertical Distal Wrap Grip and Flip with Full Curl

Jointlike Twist Self-Wipe Twist

Reaching

for food

Wiping

the trunk

ANIMAL BEHAVIOR

Trunk Tricks

Elephants build simple actions into complex motions,

intriguing roboticists

Elephants move their powerful trunks with

precision and complexity, delicately pick-

ing up a single leaf as easily as they heft

a log. But researchers have struggled to

explain how, exactly, the trunks manage

to do so. New research published in Current

Biology reveals part of the answer, thanks

to mo tion-capture technology typically

used to make movies.

“Elephants have evolved these amazing

organs with an infinite number of degrees

of freedom,” says lead author and Universi-

ty of Geneva biologist Michel Milinkovitch.

His team traveled to a South African ele-

phant reserve to study how the animals spe-

cifically use that freedom. The researchers

taped retroreflective markers to two bull

elephants’ trunks and put various items in

front of them. As the elephants moved the

objects around, the researchers filmed them

with a semicircle of infrared cameras, cap-

turing how the markers moved in three-

dimensional space—similar to the process

used for mapping movie actors’ movements

to computer-generated characters.

An elephant’s proboscis, like a human

tongue, is a type of muscular hydrostat: it

has no bones, so it can move in myriad ways.

The new study shows that the bulls combine

simple actions—such as curling, twisting

and elongating parts of their trunks—to

achieve complex movements. The animals

also form pseudo-joints, or rigid sections of

trunk, that they can shift from point to point.

“It’s the first time that we’ve gotten

a hint of what these more simplified com-

mands might be in elephants,” says Wil-

liam Kier, a biologist at the University of

North Carolina at Chapel Hill, who studies

trunk, tongue and tentacle movement and

was not a part of the study. “I think it is

a pretty important advance.”

This investigation into how an elephant’s

40,000 trunk muscles work together will

be invaluable for developing new, versatile

robots, says Cecilia Laschi, a roboticist at

the National University of Singapore, who

was not involved in the new study: “For

roboticists, this is sort of a dream.” A team

of engineers in Pisa using the study data

expects to have a trunklike robot proto type

in 18 months. — Susan Cosier