To unlock the hippopotamus in challenge or campaign games, you must earn a 2-1/2-star zoo fame rating for your zoo.
The hippopotamus is an African mammal that lives partly in water and partly on land. There are two species of hippopotamuses. The smaller species, called the pygmy hippo, stands barely waist-high to an adult human. Its bigger relative - known as the river or common hippopotamus or, simply, hippopotamus - is one of the world's largest and heaviest land animals, weighing up to about 4,000 kg (about 8,800 lb). Although strictly a plant eater, the hippopotamus has massive jaws with formidable tusks. The animal has an unpredictable temperament and is capable of biting through small boats and slicing crocodiles in two.
The word hippopotamus comes from two Greek words that mean "river horse". While hippos do live in rivers, they differ from horses in being artiodactyls, mammals with an even number of hoofed toes on each foot. There is also very little about their shape that is horselike. Both species of hippos have barrel-shaped bodies, stocky legs, and smooth, almost hairless skin. Their heads appear outsized and their mouths look unusually broad.
Hippopotamuses are not as numerous as they once were, but they can still have a major impact on the landscape of the areas they inhabit. In some parts of Africa, river hippos trample riverbanks and lakeshores, creating a maze of waterside paths and wallows that they use to get access to the plants they eat. Hippos spend their days lazing in or near water, emerging after dark to feed.
Hippopotamuses can close their nostrils and ears while underwater.
Before they can walk hippopotamuses can swim.
When a mother hippo floats in the water, the young calf sometimes rides on the mother's back - behavior that helps protect the young from crocodile attack.
Female hippos take on all the responsibility of looking after their young and are fiercely protective parents.