A hippo can be killed by lions, crocodiles (especially the Nile Crocodile and American Crocodile), and their own kind. Hippos do not often kill one another in the wild; it happens more frequently in captivity, where territorial disputes arise. Ungainly as it is, the hippopotamus is the world's deadliest large land mammal, killing an estimated 500 people per year in Africa. (One of George Washington's sets of false teeth was carved from hippo ivory.)