Hippopotamuses, often perceived as placid creatures, are formidable semi-aquatic mammals native to sub-Saharan Africa. They are among the largest land animals, adapting to both aquatic and terrestrial environments. While they spend most of their days submerged in water, emerging at night to graze, their size and powerful jaws contribute to their reputation. Despite their robust appearance, various factors can lead to their demise, ranging from natural challenges within their ecosystems to increasing pressures from human activities.
Natural Dangers
Hippos face threats from other animals, particularly when young or vulnerable. Nile crocodiles are known predators of young hippos, including calves. Lions and spotted hyenas also prey on young hippos. While adult hippos are generally too large and aggressive to be regular prey, cases of large lion prides successfully preying on adult hippos have been reported, although such occurrences are rare.
Aggression within their own species is a significant threat to hippos. Territorial disputes between male hippos (bulls) can result in brutal fights using their powerful jaws and tusks. These clashes can inflict severe wounds, leading to injury, infection, and sometimes death. Infanticide, where adult males kill calves, also occurs, particularly when hippo populations are dense or habitats shrink. This behavior is thought to increase male reproductive success by bringing females into estrus.
Environmental and Health Factors
Droughts pose a substantial threat to hippo mortality. Prolonged droughts cause water sources to shrink, leading to habitat loss and forcing hippos to congregate in smaller areas. This overcrowding intensifies competition for dwindling food and water, leading to malnutrition, starvation, and dehydration. Recent events in Zimbabwe, for example, saw numerous hippo deaths attributed to severe nutritional deficits during droughts, as animals moved significant distances in search of food.
Diseases and parasites also contribute to hippo mortality. During droughts, stress and concentration in fewer water bodies increase disease risk. Anthrax, for instance, causes deaths during droughts, spreading through contaminated water or carcasses.
Physical injuries from fights, accidents, or environmental hazards also make hippos vulnerable. Such injuries can fester and lead to life-threatening infections, particularly given their thin skin which is prone to wounds. Aging also makes older hippos less capable of foraging or defending, increasing their susceptibility to threats.
Human Impact
Human activities increasingly contribute to hippo deaths. Poaching for meat and ivory, derived from their canine teeth, is a significant driver of population decline. Hippo meat is valued in some regions, and their teeth are sought after as a substitute for elephant ivory, especially after bans on elephant ivory trade. This illegal hunting puts immense pressure on hippo populations, with some areas experiencing drastic declines.
Habitat loss and fragmentation, driven by human expansion and development, restrict hippo ranges. As human settlements expand and land is converted for farming, hippos lose access to grazing areas and water sources. This encroachment leads to increased human-wildlife conflict, where hippos are killed due to perceived threats or property damage. Hippos often raid crops at night, leading to economic losses for farmers and retaliatory killings. Authorities may also shoot hippos in response to crop raiding or other conflicts, further contributing to their deaths.