Humans are master impersonators—even infants can mimic the facial expressions of their friends and parents. Other socially sophisticated primates can copy others’ faces during play, with toothy grins bouncing from one gorilla or orangutan to the next. Now, scientists have captured video of the world’s smallest bear doing the same thing, the first time that a nonprimate has been shown to ape faces.
Researchers took short videos of 22 sun bears (Helarctos malayanus) spontaneously playing together over several years at the Bornean Sun Bear Conservation Centre in Sandakan, Malaysia. This diminutive bear is elusive and solitary, spending most of its life roaming the forests of Southeast Asia. But bears at the center engaged in hundreds of mostly gentle play fights, even though the enclosure was large enough that they could have kept to themselves.
The researchers divided the bears’ facial expressions into two types: an open-mouthed gape and an open mouth with a wrinkled nose and exposed teeth. Then, they watched the 3- to 5-minute videos to see whether the bears matched their playmates’ facial expressions.
Thirteen of the bears mirrored the facial expression of their roughhousing partner exactly within 1 second of seeing it, the researchers report today in Scientific Reports. The bears also surprised researchers with their social sensitivity—they made roughly 85% of their facial expressions while face to face with another bear.
The presence of these sophisticated social behaviors in the solitary sun bear suggests, say the researchers, that facial mimicry may be more common than previously thought. It also challenges the idea that only animals with complex social lives can be copycats.