You could believe a yawning hippo is drowsy or even cute. But, when a hippo yawns, it is a warning sign. Hippos yawn to display their jaws and long, sharp teeth. When the hippo feels threatened, it spreads its jaws wide and adopts an aggressive posture, attacking anything who enters its area or gets too close to its young, even crocodiles.
Even the sound or call of a hippo, which resembles a deep and demonic chuckle or laughs, is a warning. Conversations between hippo can travel great distances, from one pod to the next in a chain. Their honks, groans, and roars, among other things, express authority and claim territory.
As big groups of hippos all honk in concert, this epic symphony of noises can be tremendously loud. It can reach decibel levels of up to 115 (about the same as a full-fledged rock concert) and can be heard from a mile away.
While certain hippo sounds are deafeningly loud, others are completely inaudible to humans. Parts of their communication are carried out at extremely low frequencies, known as infrasound. These sounds are so deep that they are beyond human hearing range.
Despite its amusing appearance, the hippo is one of the most dangerous animals in Africa, with long sharp teeth that can reach 50 cm in length.
A hippo can extend its jaw up to 180 degrees. Females use the mouth of the hippo to choose their partner. The wider the mouth of a male hippo, the greater the male’s ability to defend the territory and the young, and so it is more appealing to females’ eyes.