|Geographical Range||Sub-Saharan Africa|
|Habitat||Rivers and lakes with surrounding grasslands|
|Scientific Name||Hippopotamus amphibius|
Fat -- but Fast!
Hippos are the second-largest land animal -- second only to elephants. Male hippos can weigh more than 6,000 pounds. Females are more "delicate," topping out around 3,000 pounds. Despite their massive bulk, hippos can run faster than humans -- up to 30 miles per hour!
Made for Water
A hippo spends most of its life in the water, and its body is well-suited to a liquid lifestyle. Blubber makes the animal buoyant, so it can float. And its skin oozes a pink "slime" that protects the hippo from sunburn, both in and out of the water.
The hippo's head is also well adapted for aquatic life. Its eyes sit on top of the head, so the hippo can get most of its body under water and still see what's going on above water. The nostrils are also located on top of the muzzle so the hippo can stay mostly under water and still breathe and sniff the air. When the hippo submerges, the nostrils close to keep out water.
The ears sit high on the head, so the hippo can still hear what's going on above water when it's mostly underneath. If the whole head goes under, the ears swivel to shake out water when the hippo resurfaces. But what about sounds below the water? That's a job for the hippo's jawbone, which conducts sound waves. So a hippo with its jaw submerged can hear sounds above and below water at the same time!
And one more way a hippo is adapted for life in the water: it can hold its breath for up to five minutes.
Hungry, Hungry Hippos
Hippos spend most of their days in or near the water in groups called pods. In the evenings, pods break up and the hippos leave the water, either singly or as females with their calves. They wander as much as three miles from the water in search of food.
Hippos spend most of the night eating grass. They use their wide mouth like a lawnmower, grazing the grass down to a few inches from the ground over a large area. A hippo can eat up to 90 pounds of grass in one night!
Hippos are so aquatic that females even give birth in the water! The babies, weighing 50 to 100 pounds, surface right after birth to take their first breath.
For the first year of their life, the youngsters nurse -- either under water or on land, depending on where mom is when they get hungry. After they're weaned, calves remain with their mothers until fully grown, at about eight years of age.
Females, Bachelors, and Territorial Bulls
Female hippos and their calves gather into groups during the day. But when they leave the water at night, groups breaks apart and each female goes off with her own calves to graze.
Most males hang out in bachelor groups. But a small percentage of males (about 10% of the population) are territorial. Each territorial bull defends his own stretch of land along the water's edge. Along with the real estate come exclusive mating rights to all females who live in his domain.
The territorial male will allow bachelor males to wander into his territory, providing they know who's boss and behave submissively. If a bachelor male challenges the territory holder, a bloody battle can break out. Dagger-sharp canines, up to 20 inches long, can seriously injure -- or even kill -- an opponent.
Hippos may not know it, but they help other animals that live in their habitat. As they walk from the water to their grazing grounds, hippos create well-worn paths. Other animals use these paths, too. And when hippos "mow" grass, they create hippo lawns. Other animals, like gazelles, benefit from the new green shoots that grow there.
When hippos return to the river, they help the fish who swim there. How? Hippos defecate in the water, and their tail acts like a "manure spreader," shooting dung everywhere. Small fish, snails, and other little critters gobble up the nutrient-rich dung -- and are themselves eaten by larger fish. Downriver, people and other animals catch and eat the fish. They can thank a hippo for their food!
What's Happening to Hippos?
Hippos are threatened in the wild. In the last 10 years, their numbers have declined by up to 20%, and it's estimated that as few as 125,000 hippos remain in Africa. More important than the total number of hippos, however, is their distribution. The Democratic Republic of the Congo and West African countries have seen the sharpest hippo declines; if the trend continues, the hippo could become extinct in these areas.
Hippos are hunted for their meat and for their canine teeth. There is an increasing demand for hippo teeth in the illegal ivory trade, due largely to the ban on elephant ivory. Many items that appear to be carved from small elephant tusks are in fact made from hippo canines.
Another problem is habitat loss. As people move into hippo habitat, they come into conflict with the animals, which raid their crops. Some of these hippos are shot and killed. Others escape wounded -- and dangerous. Rampaging hippos can attack and kill people on land or in the river.
What's being done to help hippos? Since 1995, the international trade in hippos and hippo products has been severely restricted. Nevertheless, poaching remains a serious problem. There is a need for long-term protection of national parks and other hippo habitats if these animals are to survive.
- Hippos can't sweat, so staying in water helps them keep cool.
- A hippo's bellow can be louder than a heavy-metal band playing 15 feet away.
- Hippopotamus means "river horse" in Greek, but the animal is more closely related to the pig than the horse.