Antarctic krill (Euphausia superba) are small crustaceans inhabiting the Southern Ocean, yet they collectively represent a colossal biomass. These shrimp-like creatures form immense swarms that can span hundreds of square kilometers. With an estimated total biomass ranging from 60 to 420 million metric tons, Antarctic krill stand as one of the planet’s most abundant animal species. They play a fundamental role in the Antarctic ecosystem, converting phytoplankton into food for a diverse array of larger marine animals.
Mammalian Krill Eaters
Many marine mammals in Antarctica rely heavily on krill. Baleen whales are particularly prominent krill consumers, utilizing unique filter-feeding mechanisms. Blue whales (Balaenoptera musculus), the largest animals on Earth, can ingest up to 16 tons of krill daily. Fin whales (Balaenoptera physalus), humpback whales (Megaptera novaeangliae), and minke whales (Balaenoptera bonaerensis) also depend significantly on krill.
These whales possess baleen plates, which are comb-like structures made of keratin that hang from their upper jaws. They engulf vast quantities of water containing krill, then use their tongues to force the water out through the baleen, trapping the krill inside. Humpback whales sometimes employ a cooperative hunting technique called bubble-net feeding, where groups release bubbles in a circular pattern to concentrate krill before surfacing to engulf them.
Several seal species also consume krill, with varying degrees of specialization. Crabeater seals (Lobodon carcinophaga) are the most numerous seal species globally, with populations estimated between 7 million and 75 million individuals. Their diet consists almost entirely of krill, often exceeding 90%. These seals possess uniquely lobed teeth that interlock to form a sieve, allowing them to strain krill efficiently from the water.
While leopard seals (Hydrurga leptonyx) are known predators of penguins and other seals, krill can form a portion of their diet, particularly for younger individuals. Weddell seals (Leptonychotes weddellii) primarily eat fish and cephalopods, but also include krill in their diet.
Avian Krill Eaters
Antarctica’s diverse bird populations also depend significantly on krill as a food source. Several penguin species rely heavily on these crustaceans. Adélie penguins (Pygoscelis adeliae) are highly dependent on krill, especially during their breeding season. Chinstrap penguins (Pygocelis antarcticus) derive over 90% of their diet from krill. Gentoo penguins (Pygoscelis papua) also consume krill, though their diet can be more varied, including fish and squid.
Penguins are pursuit divers, using their powerful flippers to “fly” through the water and catch krill. They often forage in groups, diving to depths that allow them to access krill swarms.
Other seabirds in the Antarctic also incorporate krill into their diets. Various petrel species, such as Antarctic petrels (Thalassoica antarctica) and snow petrels (Pagodroma nivea), forage for krill, often near the surface of the ocean. Albatrosses, including the wandering albatross (Diomedea exulans), consume krill, though fish and squid often make up a larger part of their diet. Skuas (Stercorarius species), opportunistic predators and scavengers, may also feed on krill directly or by preying on other krill-eating birds.
Fish and Invertebrate Krill Eaters
Numerous fish and invertebrate species also consume substantial amounts of krill. Antarctic silverfish (Pleuragramma antarcticum) are a dominant fish species in the Southern Ocean and are significant consumers of krill, particularly juvenile krill. Other pelagic fish species, including various notothenioid fish, also rely on krill as a major dietary component within the water column.
Cephalopods, particularly squid, are another important group of krill predators. Various squid species found in the Southern Ocean, such as the Antarctic flying squid (Todarodes filippovae), actively hunt krill. The total volume of krill consumed by these groups, including fish and squid, is substantial, potentially rivaling the consumption rates of whales and seals in certain areas.