Do Seals Eat Krill? Surprising Facts Uncovered

Seals have diverse diets, consuming fish, squid, and crustaceans. However, not all seals eat the same prey, raising the question of whether they consume krill—tiny shrimp-like creatures essential to marine ecosystems. Some seal species primarily hunt larger prey, while others rely heavily on krill. Identifying which seals consume krill and how they capture it provides insight into their ecological roles and survival strategies.

Variation In Seal Diet Worldwide

Seals inhabit a broad range of marine environments, from the Antarctic to temperate and tropical coastlines. Their diets vary based on regional prey availability, with some species primarily hunting fish, while others focus on cephalopods or crustaceans. This adaptability allows them to thrive in diverse ecosystems, adjusting to seasonal shifts in prey abundance and competition with other marine predators.

In polar regions, where nutrient-rich waters support vast krill populations, some seals have evolved to exploit this resource. The Southern Ocean hosts species that specialize in krill consumption, benefiting from dense swarms in frigid waters. In contrast, seals in temperate and tropical regions rely more on fish and squid due to lower krill concentrations. Ocean currents, temperature fluctuations, and human activities, such as commercial fishing, also influence prey availability and marine food web dynamics.

Even within the same species, diet can vary by location. For example, harbor seals (Phoca vitulina) in the North Atlantic primarily consume fish like herring and cod, while North Pacific populations incorporate more cephalopods. Some seals also shift their feeding habits seasonally, targeting different prey during breeding or migration when energy demands change.

Common Species That Consume Krill

Certain seal species rely heavily on krill, particularly in the Southern Ocean, where krill swarms provide a stable food source. These seals have developed specialized feeding strategies to efficiently consume these small crustaceans.

Leopard Seals

Leopard seals (Hydrurga leptonyx) are known as apex predators, preying on penguins and other seals, but they also consume krill, especially when larger prey is scarce. Younger leopard seals and those in certain Antarctic regions incorporate significant amounts of krill into their diet. They use a filter-feeding technique similar to crabeater seals, employing lobed teeth to strain krill from the water. This dietary flexibility helps them adapt to seasonal prey fluctuations. Research in Marine Ecology Progress Series (2010) found that krill can comprise a substantial portion of a leopard seal’s diet, particularly in areas with high competition for fish and penguins.

Crabeater Seals

Crabeater seals (Lobodon carcinophaga) are among the most specialized krill consumers. Despite their name, they primarily eat Antarctic krill (Euphausia superba). Their teeth feature intricate cusps that function as a sieve, allowing them to efficiently filter krill from seawater. By taking in large mouthfuls of water and expelling it while trapping krill, they consume vast quantities of these crustaceans. Estimates suggest crabeater seals collectively consume hundreds of millions of tons of krill annually. A study in Polar Biology (2012) found that krill can make up over 90% of their diet. Their ability to exploit krill-rich waters has contributed to their large population, estimated at over 7 million individuals.

Antarctic Fur Seals

Antarctic fur seals (Arctocephalus gazella) also consume krill, particularly in areas where it is abundant. Unlike crabeater seals, which rely almost exclusively on krill, fur seals have a more varied diet that includes fish and squid. However, during peak krill seasons, they shift their feeding behavior to take advantage of dense swarms, diving 30–50 meters to locate concentrated patches. Research in the Journal of Experimental Marine Biology and Ecology (2015) found that krill can constitute over 70% of their diet in certain regions, such as South Georgia and the Scotia Sea. Their dependence on krill makes them vulnerable to population fluctuations caused by climate change and commercial fishing.

Physical Adaptations For Krill Consumption

Seals that specialize in krill feeding have evolved anatomical and physiological adaptations to efficiently capture and process these small crustaceans. Their skull structures, dentition, and diving capabilities have been shaped by evolution to maximize krill consumption.

One of the most notable adaptations is the specialized teeth found in certain krill-feeding seals. Crabeater seals possess uniquely lobed molars that interlock to form a natural sieve. By expelling water through their teeth after taking in a mouthful, they trap krill efficiently, functioning similarly to baleen whales. Leopard seals, despite their reputation as formidable predators, also use their multi-cusped molars for krill filtration when necessary, demonstrating dietary flexibility.

Diving abilities also play a crucial role in accessing krill-rich waters. Antarctic fur seals can dive 30–50 meters, where krill swarms are most concentrated. Their streamlined bodies and powerful forelimbs enable efficient underwater movement, while advanced oxygen storage capacity allows extended dives. Additionally, their highly sensitive whiskers, or vibrissae, detect subtle water movements caused by krill swarms, guiding them to the most productive feeding grounds even in low-visibility conditions.