A large, herbivorous, semi-aquatic mammal (family Hippopotamidae) with an almost hairless, barrel-shaped body and a large mouth that opens very wide to reveal tusk-like canine teeth. The common hippo (Hippopotamus amphibious, with several subspecies) is gregarious, highly aggressive, unpredictable, and can run at 30 km/h over a short distance. It occurs throughout sub-Saharan Africa. The pygmy hippo (Choreopsis liberiensis) is nocturnal, reclusive, solitary, and not aggressive. It occurs in West Africa.