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Unna: Female, born August 12, 1989 at St. Louis Zoological Park. She arrived at the Zoo on June 28, 1990.
Cindy: Female, born July 7, 1989 at Granby Zoo in Montreal. She arrived at the Zoo on October 10, 1990.
Hippos have grayish skin with short, fine hairs that sparsely cover their bodies. They have specialized pores that ooze an oily pink substance, which protects their sensitive skin from water loss and sunburn. Early explorers thought that hippos sweat blood, but what they were seeing was really this secretion. Their bodies are barrel shaped and their legs are short, but they are surprisingly quick both on land and in the water. Their eyes, ears and nostrils are all set up high on the top of their heads so that they can remain safely submerged, just barely breaking the surface to survey their surroundings.
Hippos have enlarged incisors and long, curved lower canines (tusks) that grow continuously throughout the animal's life. These tusks are kept extremely sharp by rubbing against the shorter upper canines, and in large males they can reach 18 inches in length. As protection has increased for elephants, poachers have turned to hunting hippos for these tusks. Their numbers have declined rapidly in most areas.
In captivity and in the wild, hippos are long-lived animals that mature slowly and have calves every other year. A typical lifespan in zoos is 33 for males and 37 for females, although some individuals have reached 50 years. Lifespan in the wild is not well known.
After a gestation of about 8 months a female hippo gives birth to a single calf either on land or in shallow water. The mother and calf stay together for about two weeks before rejoining the herd. Female hippos are extremely protective and do not hesitate to attack anything that they consider to be a threat to their calf, even other hippos. The calves nurse underwater, surfacing every few seconds to take a breath, and are weaned by 8 months. The bond between a mother and her daughters remains strong for several years and a cow is often followed by up to 4 of her offspring while grazing.
Hippos are socially unique in that they tolerate close contact with other hippos while in or near water, but at the same time they are highly aggressive and most hippos bear deep scars from their neighbors' tusks. At night, hippos venture out onto land on their own or with their offspring to graze on grass, avoiding other hippos.
Mature bulls hold territories along sections of a river and defend them ferociously. Hippos are known as one of the most dangerous animals in Africa, a reputation that is deserved by these aggressive males. Even boats passing through a dominant bull's territory risk attack. Crocodiles and lions may attempt to take hippo calves, but adults are usually immune to predators.
Hippos are at home in the water and can stay underwater up to five minutes. They can even sleep underwater, surfacing to take a breath as involuntarily as breathing itself. Swimming hippos are extremely graceful and in reality they gallop underwater. Although they don't appear as agile on land, they are faster than they appear and can sprint up to 18 mph (30 kph). Hippos communicate with each other both above and below the water. We can hear their loud honking calls, but underwater microphones reveal complex clicks and whistles that sound similar to dolphin vocalizations.
Head and body length: 9.5 to 14 ft (2.8 to 4.2 m)
Tail: 13.75 to 19.75 inches (35 to 50 cm).
1,440 to 7,000 lbs. (655 to 3200 kg)
In the wild and here at the Zoo hippos are herbivores. In the wild, hippos will graze on grass, herbs and leaves. Preferring to eat at night so that their sensitive skin is protected from the sun, hippos can consume around 200 pounds of food. Oddly, hippos don't really eat water plants, preferring to travel long distances from the water at night to graze on grasses. At the Zoo, the hippos are fed about 12 pounds of vegetation, mostly lettuce, herbivore pellets and as much hay as they desire (about 50 pounds a day!)
Central Africa and along the Nile River Valley in East Africa.
On the 2011 IUCN Red List of Threatened Species, the hippopotamus is listed as Vulnerable.
To learn more about the conservation efforts at the Philadelphia Zoo, click here.
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