hippopotamus, hippo yawns in water to make threat gesture. showing tusks-like teeth at serengeti in tanzania, africa

africa aggressive big body common dangerous east five game gesture habitat hairless heaviest herbivorous hippo hippopotamidae hippopotamus horse inhabit lake large looking loss mammal national native observe park poaching river safari semiaquatic serengeti shape showing stocky submerged swamp tanzania teeth threat torso tour tourism tusk unpredictable water yawn