The search for marine mammals around the South Pole often leads to confusion between the different groups of fin-footed creatures known as pinnipeds. This group includes seals, sea lions, and walruses, all adapted to ocean life but possessing distinct traits and geographical ranges. While the Southern Ocean is home to a massive population of these animals, not all familiar species are found near the Antarctic continent. Understanding the specific inhabitants requires clarifying which animals reside south of the Antarctic Convergence, the biological boundary encircling Antarctica.
The Direct Answer: Sea Lions vs. Antarctica
Sea lions, members of the Otariidae family, do not live on the Antarctic continent or the surrounding permanent pack ice. The primary range of true sea lion species is restricted to the sub-Antarctic islands, the coasts of South America, Australia, and New Zealand. The Antarctic Convergence, where cold Antarctic waters meet warmer sub-Antarctic waters, acts as a general southern boundary for their species distribution. While some individuals may occasionally stray south of this line, no sea lion species establishes breeding colonies or permanent populations on the Antarctic ice sheets or continental coastline.
The Crucial Biological Distinction
The confusion between sea lions and the seals that inhabit Antarctica stems from key anatomical differences separating the two main pinniped families. Sea lions are classified as “eared seals” (Otariids) because they possess small, visible external ear flaps on the sides of their heads. In contrast, the seals found in Antarctica belong to the “true seal” family (Phocidae), which lack these external ear structures, having only small ear holes.
A primary difference is their method of terrestrial movement. True seals have short fore flippers and cannot rotate their hind flippers forward beneath their bodies, forcing them to undulate or “flop” on their bellies when moving on ice or land. Sea lions, however, have larger, stronger front flippers and can rotate their rear flippers, allowing them to support their weight and “walk” on all fours. This difference in flipper structure also dictates how they swim, with sea lions using their front flippers for propulsion, while true seals use their rear flippers in a side-to-side motion.
Pinnipeds That Call Antarctica Home
The Antarctic region is inhabited by four primary species of true seals, all uniquely adapted to the harsh environment of the circumpolar pack ice.
Weddell Seal
The Weddell seal holds the distinction of being the world’s southernmost breeding mammal. It often uses its teeth to wear down and maintain breathing holes in the thick sea ice.
Crabeater Seal
The Crabeater seal is numerically the most abundant seal species globally. Despite its name, it feeds almost exclusively on Antarctic krill by using specialized, sieve-like teeth to filter the small crustaceans from the water.
Leopard Seal
The Leopard seal is a famous apex predator in the Antarctic food chain, known for its long, serpentine body. It aggressively hunts penguins and other seals. Despite its predatory reputation, the Leopard seal also possesses trident-shaped molars that allow it to efficiently filter krill from the water, which makes up a significant part of its diet.
Ross Seal
The elusive Ross seal is the smallest and least studied of the four ice seals. It is recognizable by its disproportionately large eyes, which may aid in hunting in dimly lit waters. This species is also notable for its complex, siren-like vocalizations made underwater with a closed mouth.