The common hippopotamus, Hippopotamus amphibius, is often portrayed here in the US as a gentle and lazy creature. This is a severe misrepresentation of these creatures which breeds a lack of respect for them. Hippos are actually one of the most dangerous animals in Africa, killing more people each year than any of the species normally considered dangerous such as crocs, lions, and leopards. Highly territorial animals, they will attack anything they consider to be a threat. This has led to many cases of hippos attacking boats in the rivers or humans on land if the human is within the hippos comfort zone or blocking the hippo from escaping to the safety of the water.

Hippos once shared a common ancestor with pigs, although the early history of the species is unknown. They do not appear in the fossil record until the lower Miocene, 24 million years ago (Estes 2012). At this point they were already more advanced than the modern common hippo. Whether the species originated in Africa or Eurasia is unknown but during the Pleistocene, 1.6 million years ago, the genus Hippopotamus was represented by species on both continents (Estes 2012). Kenya’s Lake Turkana alone held four different species of hippo, at least one of which was more advanced than the modern day common hippo (Estes 2012).

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Hippos can be thought of as socially schizophrenic. When in the water they are highly gregarious. Even the bulls, though they are highly territorial, will tolerate much closer contact than most other ungulates. On land they become completely different, acting as solitary unsociable animals while they graze. It is not known whether they became herd animals as a method of protecting calves from crocodiles or simply to accommodate the most individuals possible in a body of water (Estes 2012). Herds typically number from 10-15 animals but range from 2 in small bodies of water all the up to 150 individuals in large bodies of water.

Bulls are typically the most dangerous due to their extreme territoriality. Mature bulls, 20 years or more, will defend territories that cover 50-100m of river or 250-500m of lakeshore as their mating areas (Estes 2012). Territorial bulls will not tolerate other mature bulls in their territory, frequently attack immature males, and surprisingly often will even attack and kill calves. That is not to say females are not also dangerous. When they feel cornered or have a nearby calf females can be just as aggressive and deadly as the males. If not for the protection of their mother’s massive and powerful jaws young hippos would be easy prey for lions, hyenas, and crocodiles. However, new and expectant mothers tend to be savagely fierce (Estes 2012).


This species once covered all of Africa south of the Sahara so long as there was water deep enough to submerge in and grasslands to graze on; however the modern pygmy hippo, Heteropogon liberiensis, is evidence that at one point hippos likely started as solitary, forest dwelling animals with only semiaquatic habits. Now they are largely confined to parks and areas of low human development. A recent study estimated that current populations for the common hippo are somewhere between125,000 and 148,000 individuals (Lewison 2008). This represents a decline of up to 20% from the population estimates from 10 years earlier. The greatest threats to hippos are habitat loss and poaching which is the most severe in countries where civil unrest is common. Hippos are often poached for bush meat and their tusks. The IUCN upped the status of hippos to vulnerable in 2006 as there is little being done to stop the decline in hippos (Lewison 2008). That is not to say that organizations are not trying, it is just difficult to work to stop poaching and habitat loss especially in war torn countries.

Literature Cited

Estes, R.D. 2012. The Behavior Guide to African Mammals. 2nd ed. Berkeley: University of California Press. 240-242. Print.

Lewison, R. & Oliver, W. (IUCN SSC Hippo Specialist Subgroup) 2008. Hippopotamus amphibius. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. <>. Downloaded on 03 September 2013.