Hippopotamus (scientific name: Hippopotamus amphibius) is the largest omnivorous mammal in freshwater species, and it is also a terrestrial animal after African elephant, Asian elephant, African forest elephant, white rhinoceros and Indian rhinoceros. The average individual is 3.3 meters long, shoulder height 1.5 meters, average weight is about 1.35 tons, and average weight is 0.9. The largest wild individual weighs 2.66 tons (more than 2.7 tons of wild individuals are actually satellite data or wrong weight unit data, and the so-called 5 tons in legend is wrong weight unit). The body is thick and round, the limbs are short, with four toes, a huge head, small eyes and ears, a particularly large mouth and a small tail. The lower canine teeth are huge, 50-60 cm long, weighing 2.5 kg, and the skin is about 40-50 mm thick. Except for sparse hairs on the nose, mouth, tail and ears, the whole body skin is bare and purple-brown. Living in the tropical region of Africa, which is rich in aquatic plants, it is often composed of more than 10 animals, and sometimes it can form a large group of hundreds of animals. Most individual hippos are adult males expelled from the group; Almost all in the water during the day, eating aquatic plants, the daily food intake is more than 80 kilograms. When aquatic plants are scarce, they will go ashore at night to feed on plants, crops and even other animal carcasses, and will also take the initiative to prey on other herbivores; The stomach has three cavities, does not ruminate, is irritable, is afraid of cold and likes warm, and is good at swimming. It can sneak along the river bottom for 5 ~ 10 minutes; During the mating season, there is a struggle between males, and the pregnancy is about 8 months, and each child 1 offspring. Lactation 1 year, sexual maturity of 4 ~ 5 years old, life expectancy of 35 ~ 40 years. Distributed in Africa.