Two hippo species are found in Africa. The large hippo, found in East Africa, occurs south of the Sahara. This social, group-living mammal is so numerous in some areas hat ÒcroppingÓ schemes are used to control populations that have become larger that the habitat can sustain. The other, much smaller (440 Ð 605 pounds) species of hippo is the pygmy hippopotamus (Choeropsis liberiensis). Limited to very restricted ranges in West Africa, it is a shy, solitary forest dweller, and now rare.
The large hippos is an aggressive animal; old scars and fresh deep wounds are signs of daily fights that are accompanied by much bellowing, neighing and snorting Hippos have development some ritualized postures the huge openmouthed ÒyawnÓ that reveals formidable teeth is one of the most aggressive. With the long, razor sharp incisors and tusk like canines, the hippo is well armed and dangerous.
Hippos move easily in water, either swimming by kicking their hind legs or walking on the bottom. They are well adapted to their aquatic life. With small ears, eyes and nostrils set at the top of the head. These senses are so keen that even submerged in water, the hippo is alert to its surroundings. By closing its ears and nostrils, the adult can stay under water for as long as six minutes.
Hippos have a flexible social system defined by hierarchy and by heed and water conditions. Usually they are found in mixed groups of about 15 individuals, but in periods of droughts large numbers are forced to congregate near limited pools of water. This overcrowding disrupts the hierarchical system, resulting in even higher levels of aggression, with the oldest and strongest males most dominant. Hippos are unpredictable. If the are encountered away from the safety of water, anything that gets between them and their refuge may be bitten or trampled.
Amazingly agile for heir bulk, hippos are good climbers and often traverse rather steep banks each night to graze grass. They exit and enter the water at the same spots and graze for four to five hours each night in loop patterns, covering one or two miles, with extended forays with up to five miles. Their modest appetites are due to their sedentary life, which foes not require high outputs of energy.
A single young is born wither on land or in shallow water. In water, the mother helps the newborn to the surface, later teaching it to swim. Newly born hippos are relatively small, weighing from 55 to 120 pounds, and are protected by their mothers, not only from crocodiles and lions but from male hippos that that, oddly enough, do not bother them on land but attack them in water.
Compared to other animals, hippos are not very susceptible to disease, so unsuitable habitats; their numbers can increase quickly. Their chief predators are people, who may hunt hippos for their meat, hides, and ivory.
¯ The name hippopotamus comes from the ÒGreek HipposÓ meaning horse, these animals were once called ÒRiver Horses.Ó But the Hippo is more closely related to the pig than the horse.
¯ Hippos spend most of their day in water close to shore lying on their bellies. In areas undistributed by people, hippos lie on the shore in the morning sun.