Hippos have killed more people than any other animal in the world. The tusk-like incisors and canines grow continuously. They are ivory, valued even more highly than an elephant's because they do not turn yellow with age. George Washington's false teeth were not made of wood, as is commonly believed, but were carved from the tusks of a hippopotamus. One young is born at a time, after a gestation of around 230 days.
Births usually occur in months of heavy rainfall, but can occur year-round.
Young hippos will also bask on their mother's back.