Hippopotamuses are large, plump animals that live in herds along rivers and lakes in sub-Saharan Africa. They can grow up to 16 feet long and weigh several thousand pounds. Despite their size, hippos are agile in water and spend most days submerged to keep cool and avoid predators. At night, they emerge onto land to graze on grass and other plant matter. Hippos live together in tight-knit family groups and give birth to pink calves that remain closely bonded to their mothers.