Hitchhikers
Did you know that a gray whale can carry several hundred pounds of barnacles on its skin? Life is good for barnacles. Snug inside their hard limestone shells, they get a free ride for life. The barnacles stick out their feather feet to comb the sea and capture plankton and other food for themselves as the whales swim slowly through nutrient-rich waters. As the whales grow, the barnacle clusters grow too. Gradually the barnacles form large, solid white colonies that appear as whitish patches, especially on the whale's head, flippers, back and tail flukes. Whale biologists look at the pattern of barnacle clusters in order to tell individual grays apart. This is possible because no two barnacle clusters, like no two human's fingerprints, are alike!

Image: Keith Jones, Baja Jones Adventure Travel