While humans are split between right-handers and left-handers, elephants have a preference for which side of their trunk they use. Now scientists have discovered it is possible to determine an elephant’s “trunkedness” by looking at its wrinkles.
While, overall, the pachyderms show an almost 50:50 split in terms of which way they prefer to bend their trunks, scientists have found it is possible to determine an individual adult’s preference.
The team say a left-trunker – which scoops objects towards the left side of its body – has more wrinkles and longer whiskers on the left side of its trunk, with whiskers on the right worn down by more frequent contact with the ground.
“The whisker length difference is big and prominent,” said Dr Michael Brecht, co-author of the study from Humboldt University of Berlin. “The wrinkle effect is more subtle, but still significant. It indicates that wrinkle patterns are at least partially use-dependent.”
The discovery is one of a number of revelations around trunk wrinkles made by the team.
Published in the journal Royal Society Open Science, Brecht and colleagues report what they say is the most comprehensive study yet of the lifelong development of trunk wrinkles in Asian and African elephants.
The team studied both the trunks of elephants that had died as well as photographs of living elephants, finding the distance between wrinkles on the trunks of adult elephants decreases on moving from base to tip.
Asian elephants were found to have far more wrinkles on the upper side of their trunks than African elephants, with further analysis revealing that this is down to a greater number of deep fold-like wrinkles.
Brecht said it is thought wrinkles make the trunk more flexible – a bit like the folds of an accordion – adding that the theory could help to explain why Asian elephants have more trunk wrinkles.
As Brecht notes, African elephants have two finger-like structures on the tips of their trunks, which they use to grasp objects, whereas Asian elephants only have one. As a result, unlike African elephants, Asian elephants often wrap their trunk around objects to grasp them.
“For this wrapping, the trunk needs to be more flexible, and we think that’s why they have a lot more wrinkles,” said Brecht.
The team found the number of wrinkles was not equal on both sides of an elephant’s trunk, revealing that this appeared to be linked to the “trunkedness” of the animal.
And while elephants are known to have trunk wrinkles at birth, the research sheds light on how they form in the womb.
When the researchers looked at elephant foetuses, they found that between day 80 and day 150 of gestation, the number of trunk wrinkles doubled every 20 days or so, before slowing down dramatically.
“Later wrinkles are added slowly, but at a faster rate in Asian than African elephants,” the team said.
Brecht said elephant trunks are highly specialised, adding that their wrinkles are mapped on to neurons in the brainstem.
“The trunk is this insane, amazing, grasping organ that is very unusual. [It] has more muscles than any other body structure in mammals,” he said. “The only thing that compares to it is the hand.”