Hippos are endangered mainly because poachers hunt them for their meat and the ivory in their teeth. Other threats are habitat loss due to the encroachment of human settlements and the diversion of river water for agriculture.
Hippo meat is sold on the black market as a delicacy. Trade in hippo ivory went up sharply after the international ban on trading in elephant ivory in 1989. Although a majority of hippo populations inhabit protected areas such as national parks, conservation areas, game reserves and sanctuaries, poachers hunt hippos in areas where there is civil unrest or law enforcement is minimal. For instance, in the 1970s, the Frankfurt Zoological Society estimated the hippo population in Virunga National Park in the Democratic Republic of the Congo to be about 30,000. During the Second Congo War, which lasted from 1998 to 2003, Congolese soldiers, Mai-Mai rebels and other groups of militia slaughtered hippos indiscriminately, so that by 2006 there were only about 600 remaining in the park.
Increased human settlements and development near freshwater areas inhabited by hippos results in clashes between hippos and humans, as hippos are by nature extremely aggressive animals. Humans then retaliate by culling hippo populations. When the levels of rivers and wetlands drop due to irrigation of farmlands, this negatively impacts hippo habitats. The problem is exacerbated during times of drought.