Chimpanzees in Zambia adopted a habit of wearing grass in their ears
At Zambia’s Chimfunshi sanctuary in 2010, a researcher noticed a female chimpanzee named Julie putting a stiff blade of grass into her ear and leaving it there while playing, resting or grooming. The same behaviour was subsequently observed among her groupmates.
During a year of video observation, eight of the group’s twelve study subjects were recorded performing the behaviour. Across three neighbouring groups containing 82 study subjects, it was recorded only once. The animals lived in similar woodland environments.
The study, published in 2014, interpreted the pattern as a socially learned group custom with no discernible practical purpose. The grass was not being used as a food-gathering tool in the observed activity: it remained in the ear during other activities. An absence of known benefits does not, however, establish that the behaviour could not be rewarding in some way.
