The correct answer is: because Ahab’s peg leg makes marks as he walks across them.
Indeed, the ship has become a personification of Ahab’s coarse and barbaric hatred for the white whale. Not only are its planks dented due to Ahab’s peg leg, the ship has been decorated with very tribal, bony paraphernalia from all the cetaceans they have killed. Scrimshaw is used everywhere to make it look like a fierce whale-eating monster. It is described the following way in the novel:
- “She was a thing of trophies. A cannibal of a craft, tricking herself forth in the chased bones of her enemies. All round, her unpanelled, open bulwarks were garnished like one continuous jaw, with the long sharp teeth of the sperm whale, inserted there for pins, to fasten her old hempen thews and tendons to. Those thews ran not through base blocks of land wood, but deftly travelled over sheaves of sea-ivory. Scorning a turnstile wheel at her reverend helm, she sported there a tiller; and that tiller was in one mass, curiously carved from the long narrow lower jaw of her hereditary foe...A noble craft, but somehow a most melancholy! All noble things are touched with that.”
