4.

Southern Elephant Seal

Mwrounga leonina

French: Eléphant-de-mer austral / German: Siidlicher See-Elefant / Spanish: Elefante marino meridional

Other common names: South Atlantic Elephant Seal, Southern Sea Elephant

Taxonomy. Phoca leonina Linnaeus, 1758,

“ad polum Antarcticum.”

Restricted by

O. Thomas in 1911 to “Juan Fernandez,”

and further restricted byJ. E. Hamilton in

1940 to “Isla Mas a Tierra” (Chile).

This species is monotypic.

Distribution. Southern Ocean, breeding

sites are scattered on subantarctic islands,

Antarctic Peninsula, and the coast of S

Argentina.

Descriptive notes. Total length 450-500 cm (males) and ¢.300-350 cm (females); weight 1500-3000 kg (males) and c.600-800 kg (females). Newborns are ¢.125 cm in length and weigh c.45 kg. Southern Elephant Seals are the largest of the phocid carnivores and are greatly sexually dimorphic in size and shape; exceptionally large male Southern Elephant Seals may weigh ¢.3700 kg. Offspring are born with a black pelage that starts to molt near weaning when they are about three weeks old to a short silvery pelage that fades to brown dorsally and tan or yellow ventrally. Nose of male Southern Elephant Seals begins to elongate and chest and neck begin to broaden during puberty at ¢.5-6 years old. Upper and lower canine teeth of males are also much longer and more robust that those in females. Post-canine teeth in both sexes are very small and non-functional.

Habitat. Except for breeding and molting, at sea in the Southern Ocean, sometimes near the Antarctic continent, particularly males. Adult Southern Elephant Seals occur

briefly on land to breed (about one month for females and up to three months for males) and to molt (about one month), and young individuals sometimes haul-out at other seasons to briefly rest.

Food and Feeding. Southern Elephant Seals primarily eat deep-water squid and fish. Prey consists of ¢.75% squid and ¢.25% fish. Cod icefish (Notothenia spp.) of the Southern Ocean are thought to be important prey when Southern Elephant Seals are near the Antarctic continental shelf. Most feeding by males occurs over continental shelves and by females in deep ocean areas at mid-water depths. Southern Elephant Seals are prodigious divers; dive depth and duration vary during the year and between sexes, but they are normally 300-500 m deep and last 20-30 minutes. Maximum depths in excess of 2000 m and maximum durations of 120 minutes have been recorded.

Breeding. Southern Elephant Seals are highly polygynous breeders. Adult males arrive ashore in August and start to establish ageand size-based dominance hierarchies and then attempt to maintain or move up socially during the next 2-3 months, with vocal and visual threats and, more rarely, physical combat. Pregnant female Southern Elephant Seals arrive in September—October, give birth to a single offspring a couple of days later, and then nurse it for ¢.23 days before abruptly weaning it and mating. The fertilized egg develops briefly and is then dormant for about two months before the embryo attaches to the uterine wall and resumes development. Females are sexually mature at 2—4 years old, and most give birth annually until they are c.12-14 years old. Males are sexually mature at 4-6 years old but not socially mature until 9-10 years old. Few individuals of either sex live much longer than 14 years.

Activity patterns. While at sea, Southern Elephant Seals are constantly active and dive usually to depths of 400-800 m, but occasionally much deeper, spending only several minutes between each dive during their several months or foraging between breeding and molting seasons. Dives last 15-40 minutes and occasionally as long as 120 minutes. When ashore molting in summer and early autumn, Southern Elephant Seals mostly sleep and conserve energy while fasting for several weeks. During the breeding season, Southern Elephant Seals are more active butstill appear to limit their movements to conserve energy.

Movements, Home range and Social organization. When foraging at sea, Southern Elephant Seals move overvast distances in the Southern Ocean. Some individuals return to molt at the sites they breed at, although some that breed at colonies at the Falkland Islands (= Malvinas), South Georgia, and Argentina appear to haul-out to molt at sites near the Antarctic Peninsula before returning to breeding sites several months later. Except for those areas, there appears to be very little overlap in foraging areas of individuals from different breeding sites on the other subantarctic islands. Southern Elephant Seals aggregate in large numbers when ashore to breed and molt, but they are solitary when atsea.

Status and Conservation. CITES Appendix II. Classified as Least Concern on The IUCN Red List. Southern Elephant Seals were harvested for their blubber, rendered to oil, beginning in the early 1800s until numbers were quickly reduced at virtually all breeding sites, except at South Georgia where sustainable commercial sealing focusing on adult males continued in association with whaling until 1967, after which whaling stations were closed. Numbers at other colonies recovered after sealing ended but then declined substantially from the 1950s through the mid-1990s before they started increasing again. Reasons for those declines remain unknown but might have involved changes in food availability associated with oceanographic changes. No recent estimate is available throughout the entire distribution of the Southern Elephant Seal, but the worldwide population was estimated to ¢.650,000 individuals in the mid-1990s. Traditionally, three breeding populations of Southern Elephant Seals were recognized (South Georgia, Macquarie, and Kerguelen Islands), butit is now apparent that as many as five (perhaps more) distinct breeding populations exist (e.g. Valdes Peninsula and Falkland Islands, now considered distinct from the breeding population on South Georgia). Although classified as Least Concern overall, recent declines of Southern Elephant Seals in some of these areas, particularly in the southern Indian and Pacific oceans, suggest that careful monitoring to clarify their conservation status is necessary in the future.

Bibliography. Campagna (2008d), Campagna et al. (2007), Carrick & Ingam (1960), Hamilton (1940), Hindell et al. (2003), Laws (1960), Lewis et al. (2006), McIntyre et al. (2010), McMahon et al. (2005), Pistorius et al. (2004), Sanvito et al. (2007a), Thomas (1911).