adopting color of surroundings adopting colour of surroundings alert back ridge blending in blending with the environment Camouflage color changing colour changing fast moving leathery looking lizard ridge ridge spikes scales spikes animal back canada cetacean dive fin hump humpback mammal marine Megaptera novaeangliae natural nature ocean sea water whale armor armored armorment armour armoured armourment backstraps bony ridges crocodile crocodylus-porosus danger dangerous dorsal-surface estuarine-crocodile exotic fauna hide hornback huge Indo-Pacific-crocodile large largest-reptile leather leathery lethargic omnivorous opportunistic opportunistic-predator osteoderms patterns powerful predator reptile reptilian ridges rough rugged saltwater-crocodile scutes skin tail tail-scutes territorial texture textured textures