Family Hippopotamidae. Mammals found in Africa. Up to 45% of all the hippo die in their first year. A hippo"s jaw can open up to 150 degrees. Reaches a length of 2.9-5 m and weighs 1,000 to 4,500 kg. Hippopotamus is semi aquatic, spending most of the day with only its eyes, ears & nostrils above the surface of a river. During the day it feeds on aquatic vegetation.