Hippopotamus is a semi aquatic mammal belonging to the family Hippopotamus in the order Artiodactyla. Hippopotamus is the largest omnivorous mammal in freshwater. The word hippopotamus means' horse in the river ', which is the Greek term for this powerful beast. Hippos are mainly distributed in tropical regions of Africa, inhabiting swamps and reed beds near rivers. Hippopotamuses often live in groups, move around at night, and spend most of their time soaking in water. They have a gentle temperament. Hippos have a huge appetite, mainly feeding on aquatic plants such as reeds, and sometimes also on land crops such as green grass on the shore. The high value of hippopotamus's long teeth is one of the reasons for their rapid decline.