abstract age aged armor armored armorment armour armoured armourment astrochelys-radiata Camouflage carapace critically-endangered giant-tortoise herbivore hide large-tortoise leathery light longevity Madagascar mixed-light old patchy plod plodding protection protective radiated-tortoise reptile reptilian rough scaly shade shadows shell size skin slow strength strong sunlight sunshine texture textured textures tortoise tough zoo Australian-freshwater-crocodile backstraps basking bony ridges crocodile crocodilian crocodylus-johnsoni crocodylus-johnstoni danger dangerous dorsal-surface exotic fauna freshie hornback Johnston's-crocodile large leather lethargic omnivorous opportunistic opportunistic-predator osteoderms patterns powerful predator ridges rugged scales scutes tail territorial battle metal sword war reflection crocodylus-porosus estuarine-crocodile huge Indo-Pacific-crocodile largest-reptile saltwater-crocodile tail-scutes