Modified from photo by Cyril Ruoso/Minden PIctures
Chimpanzees don't forget a face - or for that matter, a behind as well. A new study by Frans de Waal of Emory University and colleagues showed that chimps have butt-recognition ability:
In a recent experiment, captive primates were able to identify photos of their acquaintances' rears and match them with the right faces.
The ability suggests that the animals possess mental "whole body" representations of other chimps they know.
Each participating chimp was flashed a picture of another's bum, with visible genitals, then shown the face of the derriere's owner and another face of the same gender.
Both males and females were successful in this anatomical match game, pairing faces and posteriors with much greater frequency than chance alone—but only if the photos showed chimps they already knew.
Link - Thanks Jessica Wolf!