There are two species of hippopotamuses: the pygmy and Nile. Both species are strong swimmers and primarily feed on vegetation. Nile hippopotamuses, however, are larger and much more common than pygmy hippopotamuses. Pygmy hippopotamuses are typically found in Liberia, and prefer swampy waters. Nile hippopotamuses, on the other hand, live only in sub-Saharan Africa, and live in clearer rivers and lakes.
Hippos spend most of their time in water, so they typically live close to slow-moving African lakes or rivers. They prefer that the body of water has both shallow portions that they can walk around in and deeper sections where they can be totally submerged. Hippos have adapted to life in the water; their eyes, ears and nostrils are located on the top of the head, allowing them to be almost completely submerged and still have their senses intact. Their eyes have a clear membrane over them, which help the hippo keep its eyes open while submerged. They also have a unique skin that must be kept wet for most of the day; if it dries out the hippo will become dehydrated. Rather than sweating, hippos give off a thick, red mucous that protects the skin from the sun and keeps it moist. Despite hippos being adapted for water, their dense bodies prevent them from being able to swim or float. Instead, they move around by walking on or pushing off of the bottom of the body of water. They can, however, stay submerged for up to five minutes.
Hippos spend most of their days in the water, but they spend most of their nights on land to look for food. Their diet is almost entirely comprised of grass and sedges. As a result, they look for a habitat that not only has a slow-moving body of water, but also one that has patches of short grasses and gently shelving beaches where they can rest close to the water. They tend to choose areas that will satisfy their feeding requirements; pure grasslands and woodlands are preferred over dense thickets or forests. Their grazing has created the phenomenon called a hippo lawn, where short, green grasses continuously grow.
The number of hippos in the wild has decreased by 20 percent in the last 10 years. Some of this loss is due to hunters, who kill hippos for their meat and ivory teeth. However, this decline in numbers is also due to habitat loss: more and more people are moving into hippo habitats, and killing them because the animals eat their crops.
