Hitchhikers: Free Rides on Gray Whales Reading and Writing Connections Look at those barnacles! Photo Keith Jones Imagine carrying a load of hitchhikers on your back that can weigh several hundred pounds! Gray whales do this all their lives. Grays are more heavily infested with a greater variety of parasites and hitchhikers than any other cetacean. Who's riding, and why? Big Batches of Barnacles Those patchy white spots you see on gray whales are barnacles. Grays carry heavy loads of these freeloaders. 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. They probably just use the slow-swimming gray as a good ride through nutrient-rich waters. Photo Keith Jones As larvae, the whale barnacles swim freely in the ocean. But they time their reproduction so the larvae are swimming in the water of the nursery lagoons when the baby whales are born. Then the larvae jump aboard the whales arriving in the lagoons--as well as the newborn calves--to start their lives as hitchhikers. The most common barnacles on gray whales are host-specific, which means they occur on no other whales. One type of barnacle, Cryptolepas rhachianecti, attaches only to gray whales. Once this type of small crustacean has settled on "its own" gray, the barnacle spends its whole life hanging onto that whale. Life is good if you're a barnacle. Snug inside their hard limestone shells, the barnacles stick out feather feet to comb the sea and capture plankton and other food for themselves as the whales swim slowly along. As the young whales grow, the barnacle clusters grow too. Gradually the barnacles form large, solid white colonies. The colonies 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! (See more about barnacles here.) A Look at Lice Whale lice are another type of whale hitchhiker. Unlike barnacles, lice are true parasites. They feed on gray whale skin and damaged tissue. The lice gather around open wounds or scars. Whale lice may spread from mother whales to their calves during birth, nursing, or other bodily contact. Up to 1000 of these parasites have been found on a single gray whale. Luckily for the lice-infested whales, other creatures go after the lice. Topsmelt are silvery fish that school in the breeding lagoons. Normally they feed on marine plants, tiny shrimps and other miniscule creatures of the lagoons. But when the whales are around, the topsmelt dine on the whales. How? Schools of these small fish pick at the barnacles and whale lice crusting up a whale's skin. Topsmelt groom whales in the calving lagoons. By ridding the whales of some of their parasites and old, flaky skin, topsmelt may be helping to cut down the resistance, or drag, that grays create as their huge bodies move through the water. The whales have a smoother ride and the topsmelt groomers get protein-rich food. SEE: All About Barnacles Try This! Journaling Question and Photo ID Activity Why do you think gray whales have more hitchhikers than any other whales? (Look for clues in the text above.) If you were a gray whale biologist trying to figure out which whale is which, how good would you be? you'd have to be able to spot differences in the unique clusters of barnacles on each whale. Give it a try! Dr. William Megill gives you step-by-step help, with lots of photos for practice! Lesson: Who is That Whale? Gray Whale Photo ID Matching   This Season Teachers Kids Orientation Registration Search Copyright 1997-2008 Journey North. All Rights Reserved. Questions or comments? Contact us.