Hippos spend most of the day in lakes, rivers, and ponds. So no wonder their full name comes from two Greek words, hippos and potamos, which mean "river horse." Well-known for their large, barrel shape and wide mouths, common hippos live in the rivers and shallow lakes of eastern and southern Africa. Their cousins, pygmy hippos, inhabit the forests and rivers of western Africa. Staying cool by staying underwater is the daytime goal of both types of hippos. At night, they eat as much of the short grasses as they can. Pygmy hippos are becoming more scarce as their habitat is being cleared for other land uses, such as farming. And although their numbers are not yet dangerously low, common hippos are threatened by poachers, who want the ivory in their teeth. Are hippos at risk of becoming extinct? Learn more in this edition of Nature Watch.