The Southern Elephant Seal (Mirounga leonina) is found in Antarctic waters, though their terrestrial activities require nuance. The elephant seal is an immense animal, with males reaching lengths up to 5.8 meters and weights sometimes exceeding 4,000 kilograms. These seals are powerful swimmers and divers that forage in the cold, nutrient-rich seas surrounding the Antarctic continent.
Distinguishing the Two Species
The name “elephant seal” refers to two distinct species: the Northern Elephant Seal (Mirounga angustirostris) and the Southern Elephant Seal (Mirounga leonina). They are separated by vast geographical distance; the Northern species inhabits the Pacific coast of North America. The Southern species, which has a circumpolar distribution in the Southern Hemisphere, is the one found near Antarctica.
The Southern Elephant Seal is significantly larger than its northern counterpart, displaying extreme sexual dimorphism. A male Southern Elephant Seal can be nearly twice the length and considerably heavier than a male Northern Elephant Seal. Both species use their proboscis, the fleshy trunk-like nose, to produce loud vocalizations during the breeding season.
Habitat and Range of the Southern Elephant Seal
Southern Elephant Seals use the Antarctic region primarily for feeding rather than breeding. They are found across the sub-Antarctic islands, which lie north of the Antarctic Convergence—the biological boundary where cold Antarctic waters meet warmer sub-Antarctic waters. These islands, such as South Georgia, Kerguelen, and Macquarie Island, host the major breeding and annual molting colonies.
Adult seals undertake vast annual migrations, traveling south from these islands toward the Antarctic continental shelf waters to forage. This migration ensures they reach highly productive areas where prey is abundant. They spend up to 80% of their lives at sea, accumulating the massive blubber reserves needed for their time ashore.
The seals rarely come ashore on the Antarctic continent itself to give birth, though they frequently visit the sea ice and coastal waters for feeding. Access to the coast is often restricted by extensive sea ice during the pupping season, making the sub-Antarctic islands the favored, ice-free locations for reproduction.
Antarctic Adaptations and Behavior
The ability of the Southern Elephant Seal to thrive in the frigid Southern Ocean is due to highly developed biological and behavioral adaptations. They are among the deepest and longest-diving non-cetacean mammals, with recorded dives reaching depths of over 2,000 meters and lasting nearly two hours. This extreme diving capability allows them to hunt deep-sea prey like squid and fish in their Antarctic foraging grounds.
Physiologically, they possess a large volume of blood and a high concentration of oxygen-carrying red blood cells and muscle myoglobin, which stores oxygen for extended periods underwater. To conserve energy, seals employ a pronounced dive response, dramatically slowing their heart rate (bradycardia). This response redirects blood flow primarily to the heart and brain, minimizing oxygen consumption in other tissues.
The seals are insulated by an extremely thick layer of blubber, which protects them from the near-freezing Antarctic waters. This blubber layer provides thermal protection and helps reduce drag, enabling efficient swimming. Their foraging behavior involves long, continuous dives with only brief surface intervals, a strategy efficient for exploiting deep-water food sources near the Antarctic ice edge.