ABSTRACT
Some marine mammal species are apex predators, meaning that as healthy adults they are not usually preyed upon by other species in the wild. Polar bears (Ursus maritimus), for example, feed almost exclusively on seals and other marine mammals without fear of other predators. Blue whales (Balaenoptera musculus) only feed on planktonic krill, but they are considered apex predators as well, as they are at the top of the food chain in their ecosystem. Both marine mammal species help to keep prey populations balanced and keep the ecosystem healthy.
