The common hippopotamus, Hippopotamus amphibius, is an iconic large semi-aquatic mammal recognized for its impressive size and unique lifestyle. Its name, derived from the ancient Greek for “river horse,” aptly describes its close association with water. This article explores the physical attributes, daily habits, social behaviors, and conservation challenges facing this fascinating creature.
Defining Characteristics
The common hippopotamus is distinguished by its massive size. Adult males can weigh around 1,500 kilograms (3,300 pounds), with some reaching up to 3,200 kilograms (7,000 pounds), while females typically weigh about 1,300 kilograms (2,900 pounds). They possess a distinctive barrel-shaped body, short, stout legs, and an enormous head with a wide mouth that can open up to 150 degrees.
Their eyes, ears, and nostrils are positioned high on their skulls, allowing them to remain above water when submerged. The skin of a hippopotamus is thick, approximately 5 centimeters (2 inches) on the flanks, and nearly hairless, appearing grayish-brown with pinkish underparts. Common hippos are native to sub-Saharan Africa, inhabiting freshwater environments such as rivers, lakes, and swamps, where the water is typically deep enough for them to fully immerse.
Life in and Out of Water
Common hippos spend the majority of their day submerged in water or mud. This behavior helps regulate their body temperature and protects their sensitive skin from the intense African sun. Their skin lacks true sweat glands; instead, they secrete a reddish, oily fluid often referred to as “blood sweat.” This substance acts as a natural sunscreen, moisturizer, and antiseptic, helping to prevent sunburn and infections. Despite their large size, hippos are not particularly good swimmers and cannot float; they move underwater by walking or “galloping” along the riverbed.
During the day, they remain largely inactive in the water, conserving energy. As dusk approaches, hippos emerge from the water to graze on land, primarily consuming short grasses. They can travel several kilometers from their water source to find food, typically eating around 40 kilograms (88 pounds) of grass per night, which is a relatively small amount given their body mass. By dawn, they return to the water to escape the heat and protect their skin.
Social Structure and Communication
Common hippos are gregarious animals, typically forming social groups or “pods” that can range from 5 to over 100 individuals, though adult males may establish territories. While they gather closely in water, grazing on land is generally a solitary activity, and they do not exhibit territorial behavior on land. Males are territorial in water, defending their stretch of river or lake, and will assert dominance through aggressive displays.
Communication among hippos involves a variety of vocalizations, including grunts, roars, and a distinctive “wheeze-honk” call that can travel over long distances. They also use scent marking by “dung spraying,” rapidly flicking their short tails to distribute feces and mark territory. Hippos are known for their aggressive and unpredictable nature, especially when threatened or protecting their young. Their wide-opening mouths and large canine tusks are used in territorial battles, which can result in serious injuries.
Conservation Status
The common hippopotamus is currently classified as “Vulnerable” on the IUCN Red List of Threatened Species. Their populations face several threats across their sub-Saharan African range. Habitat loss and degradation are concerns, often driven by agricultural expansion, human settlements, and the diversion of water resources.
Poaching also poses a threat, as hippos are hunted for their meat and for their canine teeth, which are traded as a substitute for elephant ivory. Human-wildlife conflict is another issue, particularly as human populations expand and encroach upon hippo habitats, leading to clashes over resources and increased risk to both humans and hippos. Conservation efforts include the establishment of protected areas and anti-poaching initiatives, but comprehensive action plans are still needed in many regions to ensure the long-term survival of the species.