Hippos are mammals and need to breathe air just like humans. A group of hippos is usually called a bloat, pod, or herd. The hippopotamus is generally considered the third largest land mammal (after the White … Let’s learn more about these fascinating semi-aquatic creatures! Here are 17 Interesting Hippopotamus facts. Hippopotamuses have short legs, a huge mouth and a body shaped like a barrel. Hippo facts.