Facts About Hippopotamuses
Published October 11, 2026 · FactsSeeker
Hippopotamuses are large African mammals shaped by a life spent between water and land. The river, or common, hippo is the focus here, with facts on skin, movement, feeding, social life, young, communication, and conservation pressures.
Their name points to water, not horse ancestry
The word hippopotamus comes from Greek and is commonly explained as meaning water horse or river horse. That name can mislead, because hippos are not horses; the San Diego Zoo says their closest living relatives may instead be pigs or whales and dolphins. [1]
Hippo skin needs regular moisture
Hippos spend much of the day in water because their skin needs to stay wet. They lack true sweat glands and instead release a thick red secretion often called blood sweat, which forms a moist protective layer against sunburn. [1]
Their heads are built for partial submersion
A hippo can keep most of its body underwater while still sensing the surface. Its eyes, ears, and nostrils sit high on the head, a clear membrane protects the eyes underwater, and the nostrils can close when submerged. [1]
They hold their breath but do not swim
Adult hippos can hold their breath for five minutes or longer, and they can sleep underwater by reflexively rising to breathe. Despite these adaptations, the source says hippos cannot swim or float; they move by pushing off the bottom or walking along the riverbed. [1]
They graze at night after resting by day
During daylight, hippos spend almost all their time wallowing in shallow water. After sunset they graze for about six hours, with an average nightly intake of 88 pounds (40 kilograms), described as about 1 to 1.5 percent of body weight. [1]
Hippo groups can vary greatly in size
Hippos are social and usually live in groups of 10 to 30 individuals. The same source reports much larger groups of up to 200 individuals, with a herd containing adult females, adult males, and one dominant male. [1]
Dominant males use scent and displays
A dominant male marks territory by flinging dung with a fan-shaped tail. Rival males may stand nose to nose with mouths opened up to a 150-degree angle in a display called gaping, and fights can involve tusk slashing or forceful head swinging. [1]
Young hippos face predators and adult conflict
A full-grown adult hippo has relatively few natural predators, though lions have been known to take one under some conditions. Young hippos face more risks from crocodiles, lions, hyenas, leopards, and sometimes from other hippos during violent clashes. [1]
Their teeth are weapons as well as tools of display
Hippo canine and incisor teeth grow continuously, and the canines can reach 20 inches (51 centimeters). Males especially use canines in fights, while yawning, lunging, roaring, chasing, and similar behaviors can serve as threat displays. [1]
Birth timing is linked with seasonal water patterns
Hippo breeding is linked to the dry season so most births occur during the wettest time of the year. Gestation is 8 months, and if a calf is born underwater the mother must push it to the surface because newborns hold their breath for about 40 seconds at a time. [1]
Mothers isolate briefly and can nurse underwater
Near birth, a female leaves the herd for one or two weeks to give birth and bond with her calf. She may give birth in water or on land, stays with the newborn in water for several days without eating, and nurses even underwater for about eight months. [1]
Hippos communicate with loud and varied sounds
Hippos use snorts, grumbles, wheeze-honking, and other vocalizations to communicate. Some calls have been measured at 115 decibels, which the source compares with being 15 feet from rock-concert speakers. [1]
Their habitat has been greatly reduced
The San Diego Zoo says hippos are not yet endangered, but their habitat has been greatly reduced over the last 200 years. It describes them as once common to all of Africa and now abundant only in East Africa. [1]
Human and hippo territories increasingly overlap
Male hippos defend stretches of river, so boaters entering hippo territory can face aggressive responses. Females, especially mothers with calves, can also be dangerous, and the source says growing human settlements make overlap with hippo territories more frequent. [1]
Water changes and ivory demand are major pressures
Hippos depend on waterways, so dams and water diversion for agriculture can damage the rivers and lakes they use. The source also says that after the 1989 elephant-ivory ban, demand for hippo ivory sharply increased because hippo canines are made of the same material as elephant tusks. [1]
Hippos help move nutrients through ecosystems
Hippos affect their surroundings through the waste they produce. The San Diego Zoo says that waste fertilizes the African ecosystem, and many fish eat the dung or feed on small parasites living on hippo skin. [1]
Sources & further reading
These facts refer mainly to the river, or common, hippopotamus described by the San Diego Zoo source. Where the source uses cautious language, such as may for relatives, that uncertainty is preserved here.
Sources checked 2026-10-10. Our approach to facts · Suggest a correction