It is a form of communication so sophisticated it has long been believed only humans and some great apes are capable of it.

Now, new research has found that mimicking facial expressions – widely considered a key pillar in the social success of human beings – is something the world’s smallest bears do too.

It suggests, in terms of communication at least, many other mammals may share abilities previously thought to be almost unique to ourselves – raising questions over the supposed supremacy of humankind.

The findings, in which sun bears were seen to share facial expressions in apparent bonding and shows of solidarity, came during a two-year study by researchers at the University of Portsmouth.

Marina Davila-Ross, who led the project, said: “Mimicking the facial expressions of others in exact ways is one of the pillars of human communication.

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“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.

“Because sun bears appear to have facial communication of such complexity and because they have no special evolutionary link to humans, unlike monkeys are apes, nor are they domesticated animals like dogs, we are confident that this more advanced form of mimicry is present in various other species. This, however, needs to be further investigated.”

Researcher Derry Taylor monitored 22 of the animals – native to southeast Asia – in spontaneous social play sessions.

The bears, aged up to 12, were housed in Bornean Sun Bear Conservation Centre in Malaysia in which enclosures were large enough to allow bears to choose whether to interact or not.

During hundreds of play bouts, two distinct expressions were coded – one involving a display of the upper incisor teeth, and one without. The bears were most likely to show precise facial mimicry during gentle play.

Mr Taylor said such subtle mimicking could be to help two bears signal that they are ready to play more roughly, or to strengthen social bonds.

He said: “It is widely believed that we only find complex forms of communication in species with complex social systems.

“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.”

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