A favorite subject of nature documentaries, the hippopotamus is a huge and heavy herbivorous creature. Hippos are the third largest land animals (only elephants and white rhinos are larger than them), but they are surprisingly agile in the aquatic environment.
Hippos are also notorious for their aggressive behavior towards humans: they kill about 500 people a year, making them the deadliest mammals in the world (after humans). Next, you will learn eleven more unexpected facts about hippos.

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1. There are two types of hippos

Both species belong to the hippo family (Hippopotamidae), but belong to different genera. The common hippopotamus, or hippopotamus, is more common; it lives in the water bodies of Black Africa. A smaller dwarf hippopotamus, Choeropsis liberiensis, is endangered: the number of representatives of this species is less than 2500 individuals. Pygmy hippos live in the rainforests of Sierra Leone, Liberia and Côte d'Ivoire.

 

2. Whales and dolphins are the closest relatives of hippos

 

Despite its name, which comes from Greek words meaning "river horse," hippos have nothing to do with horses. They belong to the order Artiodactyla, which includes pigs, camels and deer, as well as cetaceans (whales, dolphins and porpoines). Hippos and whales had a common ancestor that lived 55 million years ago. Hippos have many common features with cetaceans, for example, skin that is almost devoid of hair, and childbirth under water. Scientists have even found that hippos emit clicks while moving underwater, similar to the echolocation of cetaceans.

 

3. Hippos are made for water

 

Rounded bodies, large heads and small legs make hippos look like submarines. Most of their time they spend resting in lakes and rivers. At night, they go out on land to eat grass and reeds. They create entire trails, making their way through the vegetation to their favorite places. Hippos even mate and give birth while in the water.

 

4. Hippos do not know how to swim

 

Surprisingly, these semi-aquatic animals do not know how to swim. They have dense bones, because of which they drown in deep water, but they are great at walking, galloping or jumping in small rivers and lakes. Their bones weigh enough to achieve optimal buoyancy; in fact, the river becomes an ideal microgravity environment for them. Hippos can be fast, being both in the water and on land, where they can accelerate to 40 kilometers per hour.

 

5. Fish help hippos keep their skin clean

Hippos and fish enjoy symbiotic relationships in aquatic habitats. African fish, including cichlids and barbels, feed on dead cells, algae and parasites on hippopotamus skin and in the mouth. Fione, a famous female hippopotamus from the Cincinnati Zoo, these spa treatments are performed by tilapia.

6. Red "sweat" hippopotamus serves as sunscreen

Hippos are often covered in pinkish "sweat," which is not really sweat or blood. Their skin secretes two substances – red (hipposudoric acid) and orange (norhipposudoric acid) – that act as sunscreen. These pigments also have antibacterial properties against Pseudomonas aeruginosa and Klebsiella, which can cause infections.

 

7. Hippos are so dangerous that Nile crocodiles try to stay away from them