Animal Kingdom by Jack Ashby

Author:Jack Ashby
Language: eng
Format: epub
ISBN: 9780750986137
Publisher: The History Press

Before they come to blows, hippos will perform incredible ‘yawn’ displays to try and convince each other that they are too big to pick a fight against. The jaw joint and musculature allows them to open their mouths to nearly 180 degrees, which is remarkable. At rest, the orbicularis oris muscle that curves around the corners of the mouth is highly folded to stop the cheek from splitting when they yawn like this (that’s the bit of your cheek that hurts when you stretch it by opening your mouth too wide). The skull also has a pronounced sagittal crest – again like the beaver – to allow for large temporal jaw muscles, which controls the gape.

If the open-mouthed displays don’t frighten off their challenger, however, they will do battle. The two hippos clash mid yawn. It is thought that the outward-facing incisors are used to try and hold their opponent’s mouth open, while the giant canines are used for stabbing. In this respect, they are more like a deer than a beaver.

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