Sun bears mimic each other’s facial expressions Daniela Hartmann/PA Wire

The world’s smallest bears copy one another’s facial expressions as a means of communication.

A team at the University of Portsmouth, UK, studied 22 sun bears at the Bornean Sun Bear Conservation Centre in Malaysia. In total, 21 matched the open-mouthed expressions of their playmates during face-to-face interactions.

When they were facing each other, 13 bears made the expressions within 1 second of observing a similar expression from their playmate.


“Mimicking the facial expressions of others in exact ways is one of the pillars of human communication,” says Marina Davila-Ross, who was part of the team. “Other primates and dogs are known to mimic each other, but only great apes and humans were previously known to show such complexity in their facial mimicry.”

Sun bears have no special evolutionary link to humans, unlike monkeys or apes, nor are they domesticated animals like dogs. The team believes this means the behaviour must also be present in various other species.

Also known as honey bears, sun bears are the smallest members of the bear family. They grow to between 120 centimetres and 150 centimetres long and weigh up to 80 kilograms. The species is endangered and lives in the tropical forests of South-East Asia.

While the bears prefer a solitary life, the team says that they engage in gentle and rough play and may use facial mimicry to indicate they are ready to play more roughly or strengthen social bonds.

“It is widely believed that we only find complex forms of communication in species with complex social systems,” says Derry Taylor, also on the team. “As sun bears are a largely solitary species, our study of their facial communication questions this belief, because it shows a complex form of facial communication that until now was known only in more social species.”

Journal reference: Scientific Reports, DOI: 10.1038/s41598-019-39932-6