Zoo heavyweights are typically large animals, such as hippos, that are kept in zoos. Hippos, which have six letters, are one of the most iconic zoo heavyweights. They are the third-largest living land mammal, after elephants and rhinos, and can weigh up to 4, 500 kilograms. Hippos are native to sub-Saharan Africa and live in rivers, lakes, and swamps. They are herbivores and spend most of their days in the water.