The mostly aquatic Hippo (hippopotamus amphibius) is the second largest terrestrial mammal after the elephant, often weighing 8,000 pounds (3,600 kg) or more. About 25% of a hippo's weight consists of a tough layer of skin, which includes a substantial amount of fat. Hippos can grow to 14 feet (4.3 m) or more in length and 5 feet (1.5 m) in height.
While hippos live in some of the hottest climates in the world, they do not have sweat glands and will rapidly get dehydrated on land. To survive the heat, hippos spend most of the day in the water. Over time the hippo has developed specialized nostrils that are located high on their snout which allow them to breath while nearly their entire body is submerged.
Hippos are nocturnal animals which feed at night on land, and return to the water to rest and digest food during the day. With little else to do during the day, hippos engage in a number of interesting territorial behaviors. Threat displays such as yawning (which expose the hippo's large teeth), charging and dung showers are common.
A dung shower!? What's that?
Hippos were formerly found near water in all areas south of the Sahara. Today, this range has been substantially reduced by human population growth.
Hippos are impressive in size and interesting to watch, but their territorial nature makes them dangerous to humans. Although they are herbivores, hippos have strong jaws and large teeth (up to 10 inches (25 cm)) and every year kill a number of people who venture too close.
Hippos are generally silent when on land, but make a distinctive honking call when they are submerged. This call is one of the most distinctive of all African wildlife.
A hippo in water will make frequent dives, surfacing every couple of minutes to breath. A mature hippo can stay under water for as much as 5 minutes, if necessary. On land, the hippo will generally walk or trot slowly, although they can move as quickly as 18 mph (30 kph) when frightened. Given their tremendous girth, the hippo cannot jump and, when possible, avoids stepping over obstacles.