There are two species of hippos, semi-aquatic mammals of the Hippopotamide family. Its Greek name, Hippopotamus amphibious, means river horse. Hippos are tied with the rhinoceros for the spot as the third-largest living land mammal.
A river, or common, hippopotamus is native to the sub-Saharan section of Africa. They remain in nearby lakes and rivers during day hours and graze on land during the evening hours when it is cooler. One hippo can eat 100 pounds (45.36 kg) of food in one day.
The common hippopotamus species tends to remain in large groups of 15 or more. Females are in greater number than males. A female can weigh about one and a half tons (1360.78 kg), while males can weigh an average of three tons (2721.55 kg). They have thin gray skin that closely resembles elephant skin. It secretes a pink oil substance to protect the hippo from sunburn and keep the skin from drying out.
A pygmy hippopotamus is smaller than the common species. It will only weigh about one quarter of the weight and half the height of the larger species. Their skin is similarly thin but is more brown or black in color. The pigmy hippo differs from the river hippo by its thinner bones and sloping spine. Although the pigmy species is also semi-aquatic, their habitat differs because they prefer the swampy forest regions of western African.
Hippopotamuses, regardless of the species, reproduce and give birth in the water. Calves are born after an eight month gestation period, and also nurse underwater. Females in the herd share babysitting and protection duties.
Male, and sometime female, hippos are aggressive and territorial. Although the hippopotamus will anger easily in the water with the herd, grazing is often done alone. While on land, the hippo does not act so aggressively.
A hippo will open its mouth very wide to expose its large teeth. Researchers believe this is an intimidation tactic the hippopotamus does try to scare off rivals or predators. Once engaged in a battle, the hippos ram into each other with their mouths wide open. They throw water with their lower jaws and head butt each other as well.
General populations of both species of the hippopotamus are in danger. The pigmy species has a significantly lower population count, but both are suffering. These animals are being hunted for their meat and their ivory teeth.