Prey Capture and Processing in Fur Seals, Sea Lions and the Walrus

Abstract

Otarioids (fur seals, sea lions and the walrus, Odobenus rosmarus) are an ancient group of marine mammals that have adapted to feeding in water in a variety of ways. Fur seals and sea lions (otariids) primarily feed on fish and cephalopods, but opportunistically target a wide range of prey types and sizes, including sharks, penguins, and even their own kind. Like their terrestrial carnivoran relatives, otariids primarily rely on their teeth to catch and process their food. Suction—the ability to lower the pressure inside the oral cavity to draw in water and prey—also plays an important role, however, especially when ingested items are small. Osteological adaptations for suction are seemingly absent, but the behavior is nonetheless facilitated by the shape of the soft tissues surrounding the mouth. Walruses are suction specialists, as reflected in their robust skull, muscular lips and strong throat muscles. They primarily feed on benthic bivalves, gastropods and annelids, but sometimes also target larger prey, including birds and other pinnipeds. Their foraging activities affect vast areas of the (sub)Arctic seafloor, affecting the structure of benthic communities and leading to major increases in nutrient flux. These large-scale effects, plus a voracious appetite, make walruses a major ecosystem engineer.