The gape-mouthed territorial display of a dominant male hippopotamus, such as this one on the Zambezi River, looks more like a colossal yawn.

• 雄性河马为守卫自身活动地域，常以大张嘴巴来显示自己的权威。正如图中这只赞比西河河马一般，这样的示威更像是大打哈欠。