Harbor seals primarily consume fish, shellfish and crustaceans, according to the National Oceanic and Atmospheric Administration Fisheries Office of Protected Resources. However, MarineBio states that their diet varies by both location and with the season. In some areas, salmon and related species are important prey for the seals.
Harbor seals attain significant size. While females are slightly smaller, large males reach 6 feet in length and 245 pounds in weight. This enables the seals to consume relatively large prey. Harbor seals tear their food into small pieces and then swallow the pieces whole. According to MarineBio, adult harbor seals consume about 5 to 6 percent of their body weight in food each day. While harbor seals are known to dive as deep as 1,500 feet and stay submerged for more than 25 minutes, most of their prey is captured and eaten in shallow water.
Harbor seals are “true seals,” which are characterized by the lack of external ears and highly modified front flippers that prevent the seals from traveling well on land. Supremely adapted to their marine lifestyle, adult harbor seals mate in the ocean. Newborn harbor seals can swim within minutes of their birth.
Harbor seals have many predators, including sharks and killer whales. Additionally, humans cause the deaths of many seals through hunting activities and habitat destruction.