Which African animal is known as the river horse?

The hippopotamus, from the Greek for river horse, which is a poor guess at its relatives - the nearest living ones are whales and dolphins, from a common ancestor about 55 million years ago. Its closest land relatives are pigs, and it is not remotely a horse.

It is also the most dangerous large animal in Africa, credited with more human deaths than lions, leopards and buffalo combined. They are territorial in water, can outrun a person on land over short distances despite weighing up to 1,500 kilograms, and have canine teeth over half a metre long that are used against each other rather than for eating - they are grazers, coming out at night to eat grass.

They cannot really swim. In deep water they walk or bounce along the bottom, and they sleep submerged and surface to breathe without waking. Their skin secretes a reddish fluid, historically described as blood sweat, which is neither: it is an acidic compound that works as both a sunscreen and an antibiotic, which is useful for an animal spending its day in muddy water with open wounds from fighting.