The patchy white spots that we see on gray whales are barnacles. The barnacles are just along for the ride. They don’t harm the whales or feed on the whales, like true parasites. In fact, barnacles don’t serve any apparent advantage to the whales. Barnacle and whale together form commensalism type of interaction. The barnacle living on the whales back gains safety and protection where as the whales does not either gain or lose anything from the relationship.