Pinnipeds, the group that includes seals, sea lions, fur seals, and walruses, are carnivores that feed primarily on fish, squid, krill, and shellfish. The specific diet varies dramatically across the 33 or so living species, shaped by where they live, how they hunt, and how their teeth and skulls have evolved. Some are generalist fish-eaters, others are highly specialized predators of a single prey type, and a few hunt animals as large as other seals.
True Seals: The Largest and Most Diverse Group
True seals (phocids) make up the biggest pinniped family, and their diets range from tiny krill to full-sized penguins and other seals. Most species are “pierce feeders,” meaning they grab prey with their teeth and swallow it whole or in large pieces. For the majority, the staple food is ray-finned fish: species like herring, cod, pollock, and capelin, depending on the region.
Several true seals have evolved to specialize. Crabeater seals, despite their misleading name, eat almost no crabs at all. Antarctic krill makes up roughly 96% of their diet. Their teeth have a distinctive lobed shape that lets them take in a mouthful of water and strain out the tiny crustaceans like a sieve, a feeding method more commonly associated with baleen whales than with seals.
Northern and southern elephant seals dive to extraordinary depths and feed primarily on squid and soft-bodied fish. Bearded seals forage along the ocean floor, eating a mix of clams, marine worms, snails, crustaceans, and bottom-dwelling fish. Hooded seals also feed on soft-bodied prey, with small crustaceans forming a large share of their diet.
Leopard Seals: Antarctica’s Apex Predator
Leopard seals deserve their own mention because their diet is one of the most varied of any pinniped. They are powerful enough to kill and eat penguins, fur seals, and even crabeater seals, yet they also filter-feed on tiny krill. Research tracking their seasonal diets found that during the Antarctic spring, leopard seals split their intake fairly evenly across krill (32 to 38%), fish (32 to 37%), and penguins (24 to 27%). In summer, adult females shift toward larger prey, with fur seals and penguins together accounting for more than half their diet while krill drops to about 22 to 27%.
This flexibility lets leopard seals exploit whatever food source is most abundant at a given time of year. Few other marine predators switch so fluidly between filtering tiny crustaceans and ambushing warm-blooded prey many times their size.
Sea Lions and Fur Seals
Eared seals, the group containing sea lions and fur seals, are generally opportunistic fish-eaters. Like most true seals, they use a pierce-and-swallow approach to capture prey. Their diets lean heavily on schooling fish such as anchovies, sardines, herring, mackerel, and squid, though the exact mix depends on local availability. California sea lions, for instance, shift between anchovies, sardines, and market squid as populations of those prey rise and fall along the Pacific coast.
Fur seals tend to eat somewhat smaller prey on average, including lanternfish and krill, particularly the species that forage in colder Southern Ocean waters. South American and Antarctic fur seals may consume large quantities of krill during peak abundance, supplementing with fish and squid year-round.
Walruses: Bottom-Feeding Specialists
Walruses stand apart from other pinnipeds. They are highly specialized bottom-feeders that eat almost exclusively bivalve clams and mussels. Using their sensitive whiskers to locate prey buried in the seafloor sediment, they use powerful suction to extract the soft bodies from the shells. Remarkably, walrus stomachs almost never contain shell fragments. They suck out the soft tissue so precisely that the empty shells are left behind intact, still connected at the hinge. Researchers have found as many as 6,400 individual clam siphons in a single walrus stomach, a testament to the volume of small prey they process in a single feeding bout.
Their preferred clam species include soft-shell clams and Arctic hiatella clams, both of which have shells that gape slightly open at the ends, making suction feeding especially effective. While clams dominate, walruses will occasionally eat snails, marine worms, sea cucumbers, and slow-moving bottom fish. Rare accounts describe walruses killing and eating seals or seabirds, but this behavior appears uncommon and may be limited to certain individuals.
How Pinnipeds Feed
Pinnipeds use two main strategies to capture food. Pierce feeding is the most common: the animal chases down prey and grabs it with pointed teeth, then swallows it whole or shakes it into smaller pieces at the surface. Most seals, sea lions, and fur seals hunt this way. Suction feeding is the second approach, used by walruses and several seal species including elephant seals and hooded seals. These animals generate negative pressure inside their mouths to vacuum in soft-bodied prey or pull tissue from shells. Suction feeders typically have smaller, less prominent teeth and rounder, more muscular mouths.
Leopard seals are unusual in using both methods. Their front teeth are sharp and recurved for gripping large prey, while their back teeth have interlocking lobes that can strain krill from seawater. This dual-purpose dentition is one reason they can exploit such a wide range of food sources.
What Pinniped Pups Eat
All pinniped pups start life on milk, and pinniped milk is extraordinarily rich compared to what most mammals produce. Fat content ranges from 25% to 60%, versus about 4% for cow or human milk. This calorie-dense milk fuels remarkably fast growth. Hooded seal pups, which have the shortest nursing period of any mammal at just four days, drink about 10 liters of 60% fat milk per day and gain roughly 30% of their birth weight each day during that brief window.
The transition to solid food varies by species. Some, like elephant seals, wean abruptly and fast for weeks before beginning to hunt on their own. Others take a more gradual approach. Harbor seal pups, for example, are relatively small-bodied and lack the energy reserves for a long post-weaning fast. Their mothers introduce them to small forage fish while still nursing, and the pups learn hunting behavior through extended maternal care before they become fully independent fish-eaters.