A hippo may open its mouth wide as a sign of aggression, similar to other animals such as lions and baboons. Opening their jaws gives others a flash of their fearsome set of weaponry: their teeth.
Although hippos eat vegetation, they do not use their teeth to do so. Their giant canines and incisors are used only for killing. Instead they use their huge lips to rip grass from the ground for consumption. A hippo is able to spread its lips through a jaw-dropping 150 degrees and up to 1.2 metres in width. The strength of a hippo’s jaw muscles - with a bite force of 1,825 psi - is such that it can use its fearsome teeth to bite a crocodile, human or even a small boat in half.
The skull of a hippopotamus contains tusk-like canines as long as your arm