This secretion may also have a protective function against infection. Mating takes place in water, probably due to more favorable weight conditions. Birth and nursing may also take place in the water. One, rarely two, precocial calves born. Mother may carry calf on her back in the water.
Young hippos are susceptible to predation by lions, leopards, hyenas, and wild dogs.
Adults are comparatively safe from predators. The incisors and canines are tusk-like and are continuously growing. Are amblers - legs on same side of the body move together. A hippo can remain under water 2 - 6 minutes before surfacing to breathe.