When it surfaces, it is usually with a loud hiss, a snort, or distinctive grunt that sounds like a blast from a tuba. The hippo expends far less energy during the day in the water than he would on land. An adult hippo eats more than 150 pounds of grass a night. These grazers tear up grass not with their teeth but with their lips. In the zoo, they eat zoo ration, alfalfa hay, trace minerals, and water free choice.
Hippos have a low mortality rate, and both males and females reproduce into old age.
Longevity is 40 years or so. Females usually have their first calf at about 10 years of age. A single calf is born at a time, rarely two, with a gestation period of 227-240 days. The calf weighs 60-100 pounds at birth and measures up to 3 feet long. Calves are sometimes born underwater and must swim to the surface for their first breath of air.