1. There are 2 hippo species, which are the common hippo and the smaller pygmy hippo.

2. Hippos are the 3rd largest living land mammals, right after rhinos and elephants.

3. On average, they are between 3.3 and 5 meters, or 10.8 and 16.5 feet, in length and up to 1.6, or 5.2 feet, tall, when measured at the shoulders.

4. Male hippos weigh between 1,600 and 4,500 kilograms, or 3,500 and 9,920 pounds. Female hippos weigh about 1,400 kilograms, or 3,000 pounds.

5. Wild and captive hippos live between 40 and 50 years. The oldest known hippo lived to be 61 years in captivity.

6. Their eyes, ears and nostrils are located at the top of their head. This allows them to hear, see and breathe while most of their body is underwater.

7. They have a clear membrane that covers and protects their eyes while allowing them to see underwater. Their nostrils close in order to keep water out and they can hold their breath for 5 minutes or longer.

8. They’re known to sleep underwater. They can do this by using a reflex that allows them to bob up, take a breath, and then sink back down without waking up.

9. They spend up to 16 hours per day submerged in rivers and lakes. This is because they need to keep their massive bodies cool under the hot African sun.

10. Even though they have adapted well for living in water, they’re not very good swimmers.