- CLASS: Mammalia (Mammals)
- ORDER: Artiodactyla
- FAMILY: Hippopotamidae
- GENUS: Choeropsis
- SPECIES: liberiensis
Good things come in small packages: At first glance, the pygmy hippopotamus looks like a mini version of its larger relative, the hippopotamus (also known as the river or common hippopotamus). But it differs in behavior and physical characteristics. The pygmy hippo has adaptations for spending time in the water but is much less aquatic than the hippo. Its nose and ears close underwater just like a hippo's do, but its head is rounder and narrower, its neck is proportionally longer, and its eyes are not on the top of its head.
The pygmy hippo's feet are less webbed and its toes more free than those of the hippo, and its legs are longer than its huge cousin's. The pygmy hippo's teeth are also different: it only has one pair of incisors, while the hippo has two or three.
The top layer of a pygmy hippo's greenish-black skin is smooth and thin to help it stay cool in the humid rainforest. However, the thin skin could cause the hippo to dehydrate quickly in the sun, so its skin oozes out a pink fluid that looks like beads of sweat and gives the hippo a shiny, or wet, appearance. This fluid, called blood sweat, helps to protect a pygmy hippo's sensitive skin from sunburn. Too bad we humans don't have built-in sunscreen!
Little is known about the behavior of pygmy hippos in their native habitat, but they are usually found by themselves or in pairs. With their cavernous mouth and formidable teeth and tusks, the hippos need only “yawn” at potential enemies to send them packing. Other ways to stay safe include rearing, lunging, scooping water with the mouth, and head shaking. Unlike their larger relative, pygmy hippos are shy and would prefer to flee rather than stay and fight. Leopards seem to be the only natural predator able to successfully attack pygmy hippos.
HABITAT AND DIET
Not only is the pygmy hippo much smaller than the common river hippo, but it is much rarer, found only in the interior forests in parts of West Africa, mainly confined to Liberia, with small numbers in the neighboring countries of Sierra Leone, Guinea, and the Ivory Coast. As a shy, nocturnal herbivore, the pygmy hippo eluded Western science until 1840. Even today, little is known of its habits in its native habitat.
Pygmy hippopotamuses are usually solitary but can sometimes be found in small family groups. Males, called bulls, have larger territories than cows (females) and both mark their homes with their droppings. Pygmy hippos are mainly nocturnal, resting well hidden in swamps, wallows, or rivers during the heat of the day until dark, when they leave the water to feed on land for a few hours in the cool of the night.
There is much more to learn about the pygmy hippo's herbivorous diet. Researchers believe that they most likely feed on leaves, roots, ferns, and fruits near rivers and streams. Pygmy hippos search for food on the forest floor or in swamps but can stand on their hind legs to reach food higher up in trees if they need to.
At the San Diego Zoo, our pygmy hippos are fed a super high-fiber pellet, a bit of hay, and greens.
When pygmy hippo cows are ready to breed, there is usually a bull waiting nearby. Pygmy hippos may mate in the water or on land. The breeding season is unknown, but normally one calf is born after a gestation period of six to seven months. Although common hippos give birth underwater, pygmy hippo calves are born on land. For the first few weeks, the mother tucks the calf, which looks like a large piggy bank, away in the bushes while she feeds, because the baby cannot walk well. The calf grows quickly, and at 5 months of age is already about 10 times its birth weight.
Although they are able to make noises—from a low grunt to a high-pitched squeak—pygmy hippos are usually silent. Body language is important in hippo culture. Signs of submission include lying prone and urinating while slowly wagging the tail. If alarmed, the hippo releases its breath with a loud huff.
Known to be found only in four countries in West Africa, pygmy hippos are now classified as endangered, with possibly less than 3,000 individuals remaining in their native habitat. The forests that shelter them are being cut down or burned away, and the rivers where they swim are now polluted by humans. In logged areas, humans hunt them for their meat. Fortunately, pygmy hippos breed well in zoos; however, more protection is needed, so that pygmy hippos will not vanish from their native habitats.
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