Their trunk is barrel-shaped and hairless. Bristles are present only on the muzzle and tail. The legs are short, and the head is large. Although their skeleton is adapted to carry the significant weight of the animal, the water in which they live reduces their weight by the body's buoyancy. Eyes, ears and nostrils are placed high on the skull vault, allowing these animals to become almost completely submerged in the water and mud of tropical rivers. While submerged, the animals cool down, which protects them from sunburn. Hippos are also characterized by long tusks (about 30 cm long) and four toes connected by an amniotic membrane.
