When comparative psychologist Marina Davila-Ross set out to study orangutans at a wildlife rehabilitation center in Borneo, she had no idea that she’d soon make a landmark discovery regarding an entirely different species. Still, upon finding herself drawn to the demure animals at the nearby Bornean Sun Bear Conservation Centre, the University of Portsmouth researcher decided to switch gears, focusing instead on the little-studied sun bear’s surprisingly complex communication skills.
The team 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.”
Across 372 recorded instances of play, the scientists spotted two main recurring facial expressions: One saw the animal raising its upper lip and nose to reveal the upper incisors, while the other found the bear opting to hide its teeth.
Around 20 percent of the time, the bears returned a playmate’s expression within one second of seeing it. If one bear offered up a toothy grin, its partner mirrored the exact same movement 82 percent of the time; when a toothless expression was at play, mimicking occurred closer to 72 percent of the time.
Overall, the researchers report that the sun bears were more likely to reflect facial expressions during gentle, rather than rough, play. Although the creatures are notoriously solitary in the wild, New Scientist notes that the study points toward their use of facial mimicry to indicate readiness for rough play or building heightened social bonds.
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.
Until now, humans, certain non-human primate species and domesticated dogs were the only animals known to change their facial expression in response to another’s actions. As National Geographic’s Buehler observes, the exact expression matching achieved by sun bears was thought to be an elusive behavior perfected solely by humans and gorillas.
Compared to primates and dogs, sun bears are far less social, preferring to forge their own paths rather than settle down in large hierarchical groups.
“We know they live in tropical rainforests, eat almost everything, and that outside of the mating season adults have little to do with one another,” Derry Taylor, a University of Portsmouth PhD student and co-author of the study, says in a press release. “That’s what makes these results so fascinating—they are a non-social species who when face to face can communicate subtly and precisely.”