The hippopotamus is a massive African mammal classified as a herbivore, relying almost entirely on plant matter for sustenance. This creature spends the vast majority of its day submerged in the rivers and lakes of sub-Saharan Africa to keep its thick skin moist and regulate its body temperature. Despite its semi-aquatic existence, the hippo’s primary food source is harvested from the terrestrial grasslands surrounding its habitat, not the water. This relationship between water-based rest and land-based feeding defines the hippo’s unique ecological role.
The Primary Diet: Terrestrial Grazing
The diet of the common hippopotamus consists exclusively of short, sweet grasses, making up 99% of its food intake. Hippos are highly selective grazers, preferring the fine, low-growing grasses found on the floodplains near their aquatic resting sites. They consume a surprisingly small amount of food relative to their immense body size, which can weigh between 3,000 and 9,900 pounds.
An adult hippo typically consumes between 88 and 110 pounds of grass per night, only 1 to 1.5% of its total body weight. Other large herbivores often consume 2.5% or more of their body weight daily. This low consumption rate is possible because the hippo maintains a low metabolic rate, conserving energy through its sedentary daytime routine. This strategy allows it to survive on a comparatively meager diet of low-nutrient grass.
Unique Feeding Habits and Anatomy
Hippos are strictly nocturnal feeders, leaving the water as dusk settles to begin their nightly foraging excursions. They can travel several miles inland, sometimes up to five miles (eight kilometers), to find the best grazing patches. These journeys are undertaken along established trails, and a hippo will spend roughly five to six hours dedicated to grazing each night.
The hippo’s specialized anatomy is adapted for its grazing lifestyle. Its broad, tough lips function like natural mowing blades, allowing the animal to crop the grass extremely close to the ground. Unlike many other large herbivores, hippos use their powerful lips and jaw structure to tear the grass, not their teeth to cut it. Once ingested, the grass passes into a digestive system structurally different from those of other grazing mammals.
The hippo possesses a three-chambered stomach, classifying it as a pseudo-ruminant, not a true ruminant like a cow or sheep. This system features a large foregut where microbial fermentation takes place, enabling the breakdown of cellulose in the tough grasses. Hippos do not regurgitate and chew cud, which is the defining characteristic of true ruminants.
Addressing Dietary Misconceptions and Supplements
A common misconception is that the hippopotamus consumes large amounts of aquatic vegetation, given the time it spends in the water. While aquatic plants are readily available, hippos rarely eat them, as their lips and jaw structure are poorly suited for harvesting this type of food. They are adapted for terrestrial grazing and only turn to aquatic plants during severe drought or resource scarcity.
Another persistent myth concerns their occasional consumption of meat. While hippos are herbivores, rare instances of them scavenging on carcasses or consuming other animals have been documented. This abnormal behavior is not indicative of an omnivorous diet but is usually attributed to severe nutritional stress, such as mineral or protein deficiencies, or opportunistic feeding during extreme hunger. Their digestive system is not designed to process meat efficiently, confirming their classification as herbivores.
To supplement nutrients lacking in their grass-heavy diet, hippos sometimes engage in pica, which involves eating soil or rocks. This consumption of non-food items helps them acquire necessary salts and minerals, such as calcium and phosphorus, that may be deficient in the surrounding plant life. This mineral consumption is a natural survival strategy that helps the animal maintain a balanced intake of required nutrients.