Diet: Harp seals are carnivorous mammals which tend to feed on a wide variety of food available in their natural habitat. The long list of sea animals which constitute their diet include crabs, eels, shrimp, squids, plankton, and at times, even jelly fish. As for the young ones, they most often feed on the mother's milk. Once they start venturing into the waters, their dietary habits change to the food source available in the water.