The southern elephant seal (Mirounga leonina) belongs to the order Carnivora, family Phocidae, and is the largest member of the seal family. It inhabits the Southern Ocean, breeding on remote sub‑Antarctic islands such as South Georgia, Macquarie, and the Kerguelen archipelago, and occasionally on Antarctic coasts. Adults spend most of the year at sea, diving to depths of over 1,500 m in search of prey, and return to land only for breeding, molting, and short haul‑out periods. Males are dramatically larger than females, possessing a massive proboscis that resembles an elephant’s trunk, a trait that gives the species its common name. Their thick blubber, up to 10 cm deep, provides insulation in frigid waters and fuels long fasting periods during the breeding season. Historically decimated by commercial sealing in the 19th century, the species has rebounded to an estimated global population of 600,000–800,000 individuals and is currently listed as Least Concern by the IUCN, though localized threats persist.

Southern elephant seals are highly colonial during the breeding season, forming massive harems where a single dominant male may control up to 50 females. Males establish territories on beach rookeries and engage in vocal displays and physical battles, using their massive proboscis and fore‑flippers to intimidate rivals. Females are more solitary, arriving on the beach to give birth and then nursing their pups for about 23 days before weaning. Both sexes undergo prolonged fasting periods; males fast for up to three months while defending harems, and females fast for several weeks after weaning. Outside the breeding season, seals are pelagic, undertaking annual migrations of up to 15,000 km and performing deep, hour‑long dives to capture prey. Communication includes low‑frequency vocalizations, body posturing, and scent marking, which help maintain social hierarchies and coordinate movements within the colony.

Southern elephant seals are apex predators that feed primarily on mesopelagic fish such as myctophids (lanternfish), as well as squid, krill, and occasional cephalopods. During foraging trips, they can dive beyond 1,500 m and remain submerged for up to 2 hours, using powerful hind‑flipper strokes and a streamlined body to pursue prey in the dark ocean depths. Daily food intake can exceed 30 % of body mass during intensive feeding periods, allowing them to accumulate the blubber needed for fasting during breeding and molting. Their diet varies seasonally and regionally; individuals in the sub‑Antarctic may consume more fish, while those farther south rely more heavily on squid and krill. They employ opportunistic hunting strategies, often following acoustic cues and exploiting dense prey aggregations detected by their acute hearing.

Sexual maturity is reached at 4–6 years for females and 5–7 years for males, though successful breeding in males often requires larger size and dominance. The breeding season occurs from December to February, when females arrive on the beach already pregnant after a gestation of approximately 11 months. After a brief labor, pups are born weighing 30–45 kg and are nursed for 23 days, during which they can gain up to 2 kg per day. Mothers fast throughout lactation, relying on stored blubber, and after weaning they quickly return to sea to replenish energy reserves. Pups are weaned abruptly and must fend for themselves, learning to dive and hunt within weeks. Females typically give birth to a single pup every year, and males may sire many offspring if they maintain control of a harem throughout the season.

The IUCN classifies the southern elephant seal as Least Concern, with a stable global population estimated between 600,000 and 800,000 individuals. However, several threats could impact future numbers. Climate change is altering sea‑ice extent and prey distribution, potentially reducing foraging efficiency. Commercial fisheries pose risks of by‑catch and competition for shared prey such as squid and fish. Entanglement in marine debris and ghost nets can cause injury or death. Historical over‑hunting has left a genetic bottleneck, reducing genetic diversity in some colonies. Human disturbance at breeding sites, including tourism and research activities, can increase stress and disrupt pupping success. Conservation measures include protected marine areas, strict regulation of fisheries interactions, and monitoring of population trends to ensure long‑term viability.

• The male’s proboscis can inflate with air, producing a resonant roar that can be heard up to 2 km away.
• Southern elephant seals can dive deeper than any other mammal, reaching record depths of 2,388 m.
• They can hold their breath for more than two hours, the longest recorded dive time for a mammal.
• Despite their massive size, pups can swim and dive within days of birth.
• Their blubber can constitute up to 50 % of body mass, providing essential insulation and energy reserves.