african broad-mouthed collagen creases endangered flat-mouthed folds gray grazer grey heavy herbivore herbivorous hide horns keratin large lattice structured mammal megafauna odd-toed ungulate perissodactyl placid powerful rhino rhinoceros skin snout southern white rhinoceros square-lipped rhinoceros strong thick threatened tough white rhinoceros wide-lipped rhinoceros wrinkled wrinkles calf cow junior lattice-structured mother odd-toed-ungulate offspring southern-white-rhinoceros youngster close close-up eye eye-lashes eye-lid eating feeding food Mud mud-covered muddy white-rhinoceros