How an elephant trunk wraps and lifts

Elephants are the construction cranes of the animal kingdom with the ability to move and lift unwieldy objects with their trunks.  In this experimental study, we examine the kinematics of an elephant lifting a barbell.  We show that the elephant trunk has several constraints to lift an object in this fashion.   The trunk forms an S-shape with two sections of the trunk forming arch-like shapes to resist deformation.  To resist the bar sliding from the elephant's grip, the elephant must also wrap the tip of its trunk around the bar, in wrapping angles that increase with the amount of weight.  We rationalize both the shape of the trunk and wrapping angle using mathematical models involving the trunk's elastic modulus and friction coefficient. These findings may inspire work in elephant-inspired soft robotics.