Hippopotamus

The hippopotamus (Hippopotamus amphibius) is the third-largest land mammal on Earth, after the elephant and white rhinoceros, and one of the most ecologically significant animals in sub-Saharan Africa. Despite their bulk, hippos are not closely related to pigs or other ungulates; their nearest living relatives are cetaceans, the group that includes whales and dolphins. Hippos spend the majority of the day submerged in rivers, lakes, and wetlands to regulate their body temperature, emerging at dusk to graze on grasses across several kilometers of shoreline each night.

Hippos play a structurally important role in freshwater ecosystems: their dung transfers nutrients from terrestrial grasslands into rivers and lakes, fueling the food chains that support fish populations relied upon by millions of people. The IUCN Red List currently classifies the species as Vulnerable, with population numbers declining primarily due to habitat loss, conflict with agricultural communities, and illegal hunting for their ivory teeth and meat. Political instability across parts of Central and West Africa has made enforcement of existing protections difficult, and the species has already been extirpated from several countries where it was historically present.