It gets its name from its massive size and the large proboscis of the adult male, which is used to produce very loud roars, especially during the breeding season.

A bull southern elephant seal is about 40% heavier than a male northern elephant seal (Mirounga angustirostris), which is nearly twice the weight of a male walrus (Odobenus rosmarus),[6][7] or 6–7 times heavier than the largest living mostly terrestrial carnivorans, the Kodiak bear and the polar bear.

[8][9] The southern elephant seal was one of the many species originally described by Swedish zoologist Carl Linnaeus in the landmark 1758 10th edition of his Systema Naturae, where it was given the binomial name of Phoca leonina.

The southern males also appear taller when fighting, due to their tendency to bend their backs more strongly than the northern species.

This species may also exhibit the greatest sexual dimorphism of any mammal in terms of mass ratio, with males typically five to six times heavier than females.

[13][14] For comparison, among the northern elephant seal and the sperm whale (Physeter macrocephalus)—two other large marine mammals that are highly sexual dimorphic by size—males typically outweigh females by a factor of three to four.

The width of the eyes, and a high concentration of low-light pigments, suggest sight plays an important role in the capture of prey.

While their hind limbs are unfit for locomotion on land, elephant seals use their fins as support to propel their bodies.

They are able to propel themselves quickly (as fast as 8 km/h (5.0 mph)) in this way for short-distance travel, to return to water, to catch up with a female, or to chase an intruder.

Tracking studies have indicated the routes traveled by elephant seals, demonstrating their main feeding area is at the edge of the Antarctic continent.

Suggested explanations include a phenomenon of depression following a rapid demographic rebound that depletes vital resources, a change in climate, competition with other species whose numbers also varied, or even an adverse influence of scientific monitoring techniques.

These capabilities result from nonstandard physiological adaptations, common to marine mammals, but particularly developed in elephant seals.

Due to the inaccessibility of their deep-water foraging areas, no comprehensive information has been obtained about their dietary preferences, although some observation of hunting behavior and prey selection has occurred.

Elephant seals do not have a developed system of echolocation in the manner of cetaceans, but their vibrissae (facial whiskers), which are sensitive to vibrations, are assumed to play a role in search of food.

When at the subantarctic or Antarctic coasts, the seals forage largely on deep-sea cephalopod species such as Psychroteuthis glacialis, Alluroteuthis antarcticus, Histioteuthis eltaninae, Onykia ingens, Gonatus antarcticus, Martialia hyadesi, Filippovia knipovitchi,[35][36] and other molluscs, various fish species, including lanternfish (i.e. Electrona spp.

), nothothens (i.e. Genera Lepidonotothen, Pleuragramma, Trematomus, Pagothenia,), Channichthyidsae spp., Bathylagidae spp.,[37] krill (mostly Euphausia spp.)

[42] The reasons for this are unclear, but are thought to be related to the distribution and declining levels of the seals' primary food sources.

This simultaneous collection of behavioural and environmental data, spanning more than ten years, has enabled researchers to study the impact of climate change on southern elephant seals and the Antarctic ecosystem.

[49] Generally, southern elephant seals appear to be resilient against the apparent variability in the location and productivity of frontal systems.

One of the most famous southern elephant seals was Minazo, who lived in Japan's Enoshima Aquarium from when he was a half-year old until his death in 2005 at age 11.

In his liner notes, Masami Akita suggested Minazo's frequent and demanding performances left him exhausted, contributing ultimately to his death.

Akita's intention in celebrating Minazo was to highlight the plight of captive animals used for performance before public audiences.

In late 2023, a 600-kilogram (1,320 lb) southern elephant seal nicknamed "Neil the Seal" became an internet sensation after repeatedly hauling out in residential areas in southern Tasmania, causing numerous issues such as preventing a woman from going to work by resting in front of her car.