animal black Diceros bicornis horn mammal power rhinoceros vertebrate.danger african black-rhinoceros collagen creases critically-endangered eating endangered folds food gray grazer grey heavy herbivore herbivorous herbivorous-browser hide hook-lipped-rhinoceros horns keratin large lattice-structured megafauna odd-toed-ungulate offspring perissodactyl placid powerful rhino skin snout southern-white-rhinoceros square-lipped rhinoceros strong surface texture textures thick threatened tough wrinkled wrinkles zoo ear head natural nature nostril animals armor armour beetle bug claw closeup dark detail Dynastinae grisly hair hook insect macro Oryctes rhinoceros pest pincer resistant rhino beetle Rhinoceros Beetle scale scarab beetles Scarabaeidae scary tenacious tuft