“Yet there’s plenty of evidence that the non-human urge to display pain has profound and intrinsic communicative value. Take the cries of lambs or rat pups, which will fetch their mothers to groom and lick them. Or the way squeaking and writhing mice will draw a cagemate close. That attention and comfort minimises how bad or stressful an injury feels, a phenomenon known as social buffering.

[…]

That’s the drawback to showing you’re hurting: the signs that attract friends can also draw foes. More subtle expressions of pain, like facial expressions, could be a way around this conundrum. Grimacing gets the message across to those close by, without being immediately obvious to a predator lurking in the bushes. Indeed, many of the animals that show pain on their face, like rabbits, mice or sheep, are vulnerable prey animals.”