aging endurable Galapagos tortoise giant tortoise heavy herbivore large leathery longevity old plodder plodding reptile slow and steady tortoise tough wisdom wise America animal animals Galapagos giant huge shell south turtle wild wildlife age aged armor armored armorment armour armoured armourment carapace elongated-neck giant-tortoise hide large-tortoise neck plod protection protective reptilian size skin slow strength strong texture textured textures zoo abstract appearance astrochelys-radiata critically-endangered endangered large tortoise Madagascar radiated-tortoise aldabra giant tortoise aldabrachelys gigantea eating eating grass elongated neck Seychelles