The hippopotamus is a massive semi-aquatic mammal native to sub-Saharan Africa. The hippo is classified as a herbivore, meaning its biological system is structured to process a plant-based diet. While rare, opportunistic observations of other feeding behaviors exist, the vast majority of its nutritional intake comes from vegetation. Hippos spend most of the day submerged in water to keep their sensitive skin cool, only venturing out to feed as the sun begins to set.
The Hippo’s Primary Diet
The diet of the common hippopotamus consists almost exclusively of grasses, placing them firmly in the category of grazers. They primarily seek out short, tender grasses, known as graminoids, found on land near their water sources. An adult hippo typically consumes 88 to 110 pounds (40–50 kilograms) of grass each night.
This substantial intake is necessary to fuel their immense body mass, yet it is surprisingly low relative to their size. The limited intake, roughly 1 to 1.5% of their body weight, is possible due to their highly sedentary lifestyle, which conserves energy. Aquatic vegetation plays a minimal role in their diet.
Observations of hippos consuming animal carcasses are rare and are considered opportunistic, often resulting from a nutritional deficiency. Their anatomy is not designed for hunting or regular meat consumption, reinforcing their definition as megaherbivores.
Unique Feeding Behaviors
Hippos exhibit nocturnal grazing habits to avoid the intense heat of the African sun. They emerge from the water at dusk, following established pathways to their feeding grounds. Foraging excursions often cover three to five miles (five to eight kilometers) and last five to six hours before they return to the water before dawn.
The physical act of eating utilizes their broad, muscular lips, which can measure up to 20 inches wide in males. These lips grasp and pluck short grasses, acting like a natural lawnmower. Hippos do not use their sharp incisor and canine teeth for cutting grass; these are primarily weapons for fighting and territorial displays. Instead, they tear the vegetation and use powerful back molars to grind the fibrous material before swallowing. This routine creates “hippo lawns,” areas of short, maintained grass that shape the landscape around their aquatic habitats.
Digestive System Adaptations
The hippo’s ability to efficiently process tough, fibrous grasses is managed by a specialized internal structure. They possess a multi-chambered stomach, though it differs from the four-chambered stomach of true ruminants like cattle and deer. This anatomical distinction means they are classified as pseudo-ruminants, as they benefit from foregut fermentation without chewing cud.
The stomach has three main compartments, including a large forestomach chamber where the initial breakdown of plant material occurs. This process, known as foregut fermentation, involves specialized microbes that break down cellulose, the structural component of plant cell walls. The prolonged retention of food in these chambers allows for the slow extraction of maximum nutrients from their low-energy diet. The efficiency of this system is sufficient for the hippo’s low-energy lifestyle, which is characterized by long periods of inactivity. This unique digestive physiology highlights an evolutionary adaptation for processing bulk amounts of grass. The nutrients that are eventually excreted in the water through defecation also play an ecological role by adding fertilizer to the aquatic environment.