Marine Biology

Food & Feeding

         Cetaceans are near the top of the marine food chain and are classified into two groups: those with teeth and those with baleen. Baleen, which are large stiff plates that grow down from the gums of the whale's upper jaw, allow whales to filter food. Baleen is made of keratin, the same protein that makes up hair and fingernails, and is strong, yet elastic. The whale filters (removes) plankton, krill, and small fish from seawater by squeezing water through the baleen with its tongue and then licking the plankton off the baleen. Toothed whales are hunters and use their teeth to grasp their prey, but do not chew their food. They eat fish, squid, and other marine mammals. The fringes on the baleen work like a net to trap food but let water pass back out of the mouth.

          Manatees and dugongs are herbivores. They eat only vegetation, such as sea grasses, algae, mangrove leaves, and water hyacinths.

           Pinnipeds have teeth that are sharp and good for grabbing fish and other food such as shellfish. Like the toothed whales, pinnipeds do not chew their food, but swallow it whole or in big chunks. A polar bear's favorite food is seal. If there are no seals to hunt, they will eat small whales, lemmings, and even geese. On the right is a picture of a sea otter eating an octopus. Sea otters typically float on their backs while eating, using their chest as a dining table. A tool such as a stone is used to break open the hard shells of their prey (clams and crabs) or to knock shellfish off rocks. This is one of the few known cases of an animal using tools. The sea otters have flat molars for grinding and eat mostly benthic (bottom-dwelling) invertebrates (animals with no backbones), such as clams, mussels, urchins, crabs and abalone.