Southern Elephant Seal | The World’s Largest Pinniped and Where to See Them

Both sexes are extremely robust with thick muscular necks and a substantial layer of blubber. The male’s most distinguishing feature is their inflatable proboscis, which develops at sexual maturity and is used to produce vocalisations, especially during the breeding season to assert dominance and establish their territory.

Their extreme size limits their terrestrial movement. Like other phocids they cannot support their own body weight and utilise their hind flippers when moving. Instead, when on land they get around by rhythmic undulations of their body known as, ‘galumphing’. 

Size: ♂ 4.2 - 5.7m ♀ 2.6 - 3m
Weight: ♂ 2200 - 4000 kg ♀ 400 - 900 kg
Dive Depth: 2,388 meters (max recorded)
Dive Duration: < 2 hours
Life Expectancy: Approx. 20 - 22 years

They have remarkable diving capabilities which are reflected in some of their physical traits. Very large eyes, containing high densities of rod cells, aid them to see in low-light conditions. Their highly sensitive vibrissae (whiskers) detect subtle movements in the water, crucial when foraging in the dark depths of the bathypelagic zone (1000 - 4000m), where sunlight doesn’t penetrate the water column. 

Mating battles

Males are the first to arrive at the breeding grounds, where they engage in vocal and physical bloody battles to establish dominance. Their enlarged proboscis is used in both acoustic displays and visual dominance, playing a key role in asserting control and deterring rival males.These often-brutal confrontations determine the social hierarchy and which males gain access to females. 

The most dominant males, known as ‘beachmasters’ secure exclusive mating rights and defend harems that average around 30 females but can contain in excess of 100.

Breeding and pupping

Maturity: Females typically reach sexual maturity between 2 and 6 years of age, while males mature slightly earlier, at around 4 to 5 years. However, most males will not gain access to females until they are 9-12 years old, and have developed sufficient body mass and muscle to compete effectively.

Pupping: Shortly after the dominant males have established territories, females arrive and give birth to a single pup, conceived the previous year. Gestation lasts approximately 11 months and includes a 4-month period of delayed implantation. 

From birth to weaning: Most pups are born between September and October, weighing around 40 kg at birth. Thanks to their mothers’ nutrient-rich milk, which is over 50% fat, pups gain weight rapidly, often more than tripling their mass in just 22–26 days of nursing. During lactation females fast, relying on their blubber as an energy reserve. 

Weaners and independence: Just before the pup is weaned, the female will mate again with the dominant male. After the mothers return to sea, weaned pups known as, ‘weaners’ remain on land for an additional 4 to 6 weeks. During this crucial period, they gain strength, building up their energy reserves and honing their swimming skills before their first foraging trips at sea. This extended haul-out period is vital for survival.

Deep-diving hunters

Feeding occurs almost exclusively at sea, where individuals can spend months on extended foraging trips, covering thousands of kilometres. They possess an extraordinary ability to dive to depths in excess of 2000 meters, holding their breath for up to two hours. These deep-diving capabilities allow them to exploit prey sources such as deep-water squid that are beyond the reach of many marine predators.

Rare prey encounters

Predation on small sharks appears to be a rare opportunistic behaviour. In 2008, a sub-adult was recorded consuming a draughtboard shark head-first off the southeast coast of Tasmania.

Foraging strategies: male vs female

They are solitary feeders with both sexes exhibiting different foraging behaviours and strategies. 

• Females typically travel to Antarctic waters to forage in the pelagic zone

• Males have been found to pursue benthic species travelling further south

Predators

The frequent deep-diving behaviour and lengthy migrations of southern elephant seals make it challenging to determine the complete range of predators. While adult seals are relatively safe due to their sheer size and deep-water lifestyle, pups and juveniles remain vulnerable to predation, particularly close to haul-outs and in coastal waters.

Main predators

• Leopard seal – agile hunters that target pups and young seals in shallow waters.

• Killer whales (Type A orcas) – capable of preying on juveniles and adults, particularly during migrations.

Opportunistic predators

• Giant petrels and skuas will target weak and vulnerable attended pups.

• Sharks are another potential threat, with attacks on their close relative, the northern elephant seal well documented. One study reported superficial wounds on a southern elephant seal, consistent with sleeper shark bites, indicating vulnerability to various shark species.

Protection through size and depth

Once full-grown, elephant seals face few natural threats. Their ability to dive for hours at depths over 1,000 m places them beyond the reach of most predators.

Key threats:

Southern elephant seals face several threats, primarily from environmental changes and human activities. 

Fisheries interactions

As deep divers, elephant seals are vulnerable to longline fisheries targeting Antarctic toothfish. Incidental bycatch can be fatal — one individual was documented drowned at 950 m after entanglement. Overfishing may also deplete prey stocks, though activities are regulated by the CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources).

Climate change

Global climate change is already impacting southern elephant seals, with the warming of the Southern Ocean altering their foraging and diving behaviours. Both sexes have been found to dive deeper in warmer waters, with females adjusting their dive depths significantly more than males. As the Southern Ocean continues warming, changes in ocean conditions are likely to affect prey populations, subsequently impacting the seals’ distribution and behaviour.

Avian influenza

Avian flu (HPAIH5N1) introduced by migratory birds has heavily impacted southern elephant seals. This highly pathogenic virus spread through colonies like wildlife, resulting in mass mortality. The full extent of its effects on population numbers remains unclear. In Argentina, it’s estimated that the recovery of the Valdés Peninsula population could take up to a century due to the exceptionally high mortality rates.

Fun Facts

• In 1913, the largest southern elephant seal ever recorded measuring 6.85 meters (22.5 ft) was found in Possession Bay, South Georgia. 

• During the 19th century elephant seals were almost hunted to extinction largely for their blubber, fortunately populations have rebounded.

• The male’s inflatable proboscis serves two functions: it acts as a rebreather to conserve water when they fast during the breeding season, and amplifies vocalisations intimidating rival males.

• Elephant seals are positively thigmotactic, often lying in close proximity to take advantage of the thermoregulatory benefits of physical contact. 

• On land southern elephant seals can move at speeds of around 3mph (4.8kph) and when swimming 3-6mph (4.8 - 9.6 kph).

• Once a year elephant seals haul out on the land and undergo a 'catastrophic moult,' shedding their entire outer layer of skin and fur.

• Elephant seals have large amounts of myoglobin in their muscles and haemoglobin in their blood, these two, oxygen carrying proteins act like a built-in scuba tank, aiding in their remarkable diving abilities.

• The deepest dive on record is to an astonishing depth of 2,388 meters.