The hippopotamus or hippo is a large, mostly herbivorous
mammal in sub-Saharan Africa and is the third largest land animal (after the elephant and the white rhinoceros).
Hippos measure 3.3 to 5.2 meters (11 to 17 ft) long, including a tail of about 56 centimeters (22 in) in length and average about 1.5 meters (5 ft) tall at the shoulder. Even though they are bulky animals, hippopotamuses can run faster than a human on land. Estimates of their running speed vary from 30 km/h (18 mph) to 40 km/h (25 mph), or even 50 km/h (30 mph). The hippo can maintain these higher speeds for only a few hundred meters.
The hippo is semi-aquatic, inhabiting rivers and lakes where territorial bulls preside over a stretch of river and groups of 5 to 30 females and young. During the day the hippopotamus remains cool by staying in the water or mud and then emerge at dusk to graze on grass. While hippo's rest near each other in the water, grazing is a solitary activity and hippos are not territorial on land.
Hippos are by nature very hostile animals, especially when young calves are present. Frequent targets of their aggression include crocodiles, which often inhabit the same river habitat as hippos. Nile crocodiles, lions, and spotted hyenas are known to prey on young hippos. Hippos are very aggressive towards humans, whom they commonly attack whether in boats or on land with no apparent provocation. The hippopotamus is widely considered to be one of the most dangerous large animals in Africa. To mark territory, hippos spin their tails while defecating to distribute their excrement over the greatest possible area.
Hippos have been on the list as one of the most dangerous killers in Africa for a long while now and this is more due to their territorial temperament than their nature. As with humans, the older hippos get, the more cranky they are and it is these older bulls that have been kicked out of their family group, often with mortal wounds, that cause the many deaths in Africa each year.