【動物行動学】遊び仲間の顔の表情をまねるマレーグマ

Sun bears produce facial expressions that mimic with precision those of their playmates, according to an initial study published in Scientific Reports. This facial mimicry, which seems to allow the bears to communicate in an efficient, effective and precise way, had previously not been observed in non-domesticated, non-primate species.

Marina Davila-Ross and colleagues studied the facial complexity of 22 group-housed sun bears engaged in spontaneous social play, with specific focus on exact facial mimicry - the ability to precisely match a playmate’s facial expression. The authors examined whether the bears responded to their playmates’ open-mouthed facial expressions with matching open-mouthed expressions during face-to-face interactions.

Of the 22 bears studied, 21 produced open-mouthed expressions, and 13 of these showed them within one second of observing a similar expression from a playmate when the bears were facing each other. The finding suggests that the bears modify their expressions when they are being observed by social partners, which could mean that they are sensitive to having their partner’s attention. Contrary to what has been suggested for human-associated species such as apes, which are more closely related to humans, or dogs, which live in close contact with humans; in sun bears, social sensitivity, and the associated precision in mimicking facial expressions, cannot be explained by adaptations to complex social environments, as the bears are primarily solitary in the wild.

The findings suggest that facial mimicry is more widespread than previously thought, and may not be exclusive to species with strong social tendencies.