Seals are marine mammals belonging to the order Carnivora, specifically the parvorder Pinnipedia, which also includes sea lions and walruses. These animals are aquatic predators, and their diet consists almost entirely of meat, placing them firmly in the carnivorous category. Their specific prey varies greatly depending on the species and the environment they inhabit.
Primary Food Sources
The majority of seal species are considered generalist feeders, consuming whatever prey is locally abundant in their coastal or open-ocean habitats. Fish constitutes the largest and most frequent portion of a seal’s global diet, particularly schooling varieties such as herring, cod, and mackerel. Many species also consume rockfish, flounder, and salmon.
Cephalopods, including various species of squid and octopus, also make up a significant part of the diet for numerous seal populations. These soft-bodied prey items are a rich source of protein and fat, often targeted during deeper dives. Crustaceans like shrimp and crabs are another common dietary component, particularly for younger animals.
How Diet Varies Among Seal Species
While many seals maintain a generalist diet, certain species have developed highly specialized feeding strategies driven by unique environmental pressures. The Crabeater seal of the Antarctic, despite its misleading name, is a prime example of such specialization, with its diet consisting of over 90% Antarctic krill.
Crabeater seals have evolved a highly distinctive dentition, featuring lobe-shaped teeth that interlock to form a fine sieve, allowing them to effectively filter the small, shrimp-like krill from the water. In stark contrast, the Leopard seal, another Antarctic resident, is an apex predator known for its aggressive foraging behavior. This seal is the only pinniped known to regularly hunt warm-blooded prey, including penguins and the pups of other seal species.
Coastal species like the Harbor seal and Grey seal are opportunistic hunters with regional and seasonal diet variations. These generalists primarily consume a mix of pelagic fish, sandeel, and gadids, with their diet directly reflecting the dominant fish stocks in their local estuaries and nearshore waters.
Hunting Methods and Adaptations
To successfully hunt in the marine environment, seals rely on highly developed sensory organs, particularly their vibrissae, or whiskers. These stiff, sensitive hairs can detect minute changes in water movement and pressure caused by a swimming fish or squid. This ability allows seals to track and locate prey in dark, murky, or deep waters where visual cues are nonexistent.
Their streamlined bodies and powerful flippers allow for incredible aquatic maneuverability and speed during the chase. Seals are also masters of physiological adaptation for deep-sea foraging, able to sustain long dives by slowing their heart rate and conserving oxygen. This adaptation directs blood flow primarily to the brain and other vital organs, while non-essential areas temporarily function on reduced oxygen.
Once prey is captured, most seals are adapted to swallow their food whole or tear it into large pieces rather than chewing. The specialized teeth of filter-feeding seals allow them to swim through dense krill swarms, trapping thousands of tiny crustaceans. Other species possess large canines for grasping and tearing larger prey like penguins.