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Mirounga leonina

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CARNIVORA PHOCIDAE

Scientific Name: Mirounga leonina
Species Authority: (Linnaeus, 1758)
Common Name(s):
English Southern Elephant Seal, South Atlantic Elephant-seal, Southern Elephant-seal
French Eléphant De Mer Du Sud, Eléphant De Mer Méridional
Spanish Elefante Marino Del Sur

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Campagna, C. (IUCN SSC Pinniped Specialist Group)
Reviewer(s): Kovacs, K. & Lowry, L. (Pinniped Red List Authority)
Justification:
Due to its widespread occurrence and large population size globally, the Southern Elephant Seal should remain classified as Least Concern. However, recent declines in some areas should be considered at a finer spatial/population scale.

IUCN Evaluation of the Southern Elephant Sea, Mirounga leonina
Prepared by the Pinniped Specialist Group


A. Population reduction Declines measured over the longer of 10 years or 3 generations
A1 CR > 90%; EN > 70%; VU > 50%
Al. Population reduction observed, estimated, inferred, or suspected in the past where the causes of the reduction are clearly reversible AND understood AND have ceased, based on and specifying any of the following:
(a) direct observation
(b) an index of abundance appropriate to the taxon
(c) a decline in area of occupancy (AOO), extent of occurrence (EOO) and/or habitat quality
(d) actual or potential levels of exploitation
(e) effects of introduced taxa, hybridization, pathogens, pollutants, competitors or parasites.

Generation time is approximately 9-10 years. Some populations decreased markedly in the last 50 years to levels that meet the CR criterion locally. But, in the last 30 years (assuming a generation time of 10 years), some stopped declining while others are increasing but have not as yet recovered to baseline numbers.

The most recent information available for the largest population (South Georgia) is that it is stable. One of the five most important populations (Península Valdés) has been growing and it is now apparently stable. Based on best available information, the combined size of the declining colonies do not in combination bring the global status into a vulnerable condition according to IUCN criteria.


A2, A3 & A4 CR > 80%; EN > 50%; VU > 30%
A2. Population reduction observed, estimated, inferred, or suspected in the past where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

Local population reductions have been observed in the past 30 years for not well-understood reasons.

A3. Population reduction projected or suspected to be met in the future (up to a maximum of 100 years) based on (b) to (e) under A1.

Predicted reduction in sea ice habitats due to continued climate warming will impact the distribution of food and breeding habitat for the species. Predictions are not clear yet regarding how these effects will impact the size of the populations.

A4. An observed, estimated, inferred, projected or suspected population reduction (up to a maximum of 100 years) where the time period must include both the past and the future, and where the causes of reduction may not have ceased OR may not be understood OR may not be reversible, based on (a) to (e) under A1.

A global population reduction for the species has not occurred in the past 30 years.

B. Geographic range in the form of either B1 (extent of occurrence) AND/OR B2 (area of occupancy)
B1.
Extent of occurrence (EOO): CR < 100 km²; EN < 5,000 km²; VU < 20,000 km²

Elephant Seals reproduce in colonies where harems are dispersed over a few km of coastline. Colonies may be thousands of km away from each other. Distribution at sea is over millions of square km.

B2. Area of occupancy (AOO): CR < 10 km²; EN < 500 km²; VU < 2,000 km²

See above for B1. The AOO on land is relatively small for each stock but significantly larger than the above numbers during the pelagic phases (when animals are apparently solitary and disperse widely away from breeding sites).

AND at least 2 of the following:
(a)
Severely fragmented, OR number of locations: CR = 1; EN < 5; VU < 10
(b) Continuing decline in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) area, extent and/or quality of habitat; (iv) number of locations or subpopulations; (v) number of mature individuals.
(c) Extreme fluctuations in any of: (i) extent of occurrence; (ii) area of occupancy; (iii) number of locations or subpopulations; (iv) number of mature individuals.

Besides a few colonies in the Antarctic and the temperate SW Atlantic, subpopulations are distributed among sub-Antarctic islands around the Antarctic continent, but this is the normal pattern, not the result of induced fragmentation of the population(s).

C. Small population size and decline
Number of mature individuals: CR < 250; EN < 2,500; VU < 10,000

The current abundance is > 10,000.

AND either C1 or C2:
C1.
An estimated continuing decline of at least: CR = 25% in 3 years or 1 generation; EN = 20% in 5 years or 2 generations; VU = 10% in 10 years or 3 generations (up to a max. of 100 years in future)
C2. A continuing decline AND (a) and/or (b):
(a i) Number of mature individuals in each subpopulation: CR < 50; EN < 250; VU < 1,000
or
(a ii) % individuals in one subpopulation: CR = 90–100%; EN = 95–100%; VU = 100%
(b) Extreme fluctuations in the number of mature individuals.

D. Very small or restricted population
Number of mature individuals: CR < 50; EN < 250; VU < 1,000 AND/OR restricted area of occupancy typically: AOO < 20 km² or number of locations < 5

Not applicable.

E. Quantitative analysis
Indicating the probability of extinction in the wild to be: CR > 50% in 10 years or 3 generations (100 years max.); EN > 20% in 20 years or 5 generations (100 years max.); VU > 10% in 100 years

There has been no quantitative analysis of the probability of extinction. It is unlikely that the species will meet any of the above criteria, although the effects of global warming are unknown.

Listing recommendationThe Southern Elephant Sea should be classified as Least Concern. No serious threats have been affecting the land breeding colonies of the species in the last 30 years. The foraging areas may be affected by the impact on the distribution of prey by climate change effects, although it is unknown how this may actually influence the species distribution and numbers. Some local declines are a cause for concern and should be assessed at the level of populations by the IUCN SSC Pinniped Specialist Group

Geographic Range [top]

Range Description: Southern elephant seals have a nearly circumpolar distribution in the southern Hemisphere. Although they reach the Antarctic continent and even very high latitude locations such as Ross Island, they are most common north of the seasonally shifting pack ice, especially in Subantarctic waters where most rookeries and haul-outs are located. Notable exceptions include the northern breeding colonies at Peninsula Valdés, in Argentina and on the Falkland-Malvina Islands.

Some pups are also born on the Antarctic continent. Southern elephant seals prefer sandy and cobble beaches, but will haul-out on sea ice, snow and rocky terraces and regularly rest above the beach in tussock grass, other vegetation, and mud wallows. At sea, females and males tend to disperse to different feeding grounds. Wandering and vagrant southern elephant seals reach southern Africa, southern Australia, New Zealand and Brazil in South America. An Indian Ocean record at Oman on the Arabian Peninsula represents a northernmost record.
Countries:
Native:
Antarctica; Argentina; Australia (Macquarie Is.); Bouvet Island; Chile; Falkland Islands (Malvinas); French Southern Territories (Crozet Is., Kerguelen); Heard Island and McDonald Islands; New Zealand (Antipodean Is.); Saint Helena, Ascension and Tristan da Cunha (Tristan da Cunha); South Africa (Marion-Prince Edward Is.); South Georgia and the South Sandwich Islands
Vagrant:
Angola (Angola); Brazil; Mauritius; Mozambique; Namibia; Oman; Peru; Uruguay
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: No recent integrated estimate is available throughout the entire distribution. The worldwide population of southern elephant seals was estimated to be 650,000 in the mid 1990s. Colonies in the South Atlantic, which include the largest breeding aggregation located at South Georgia, are stable or growing, while those in the Southern Indian and Pacific Oceans have decreased by up to 50%. There is some evidence that weaning mass is lower at Macquarie, Heard and Marion Islands, and Iles Kerguelen, than in the South Georgia and Peninsula Valdés (Argentina) populations, suggesting that the Indian and Pacific Ocean populations may have a reduced food supply.

Traditionally, three distinct populations have been distinguished: South Georgia, Macquarie and Iles Kerguelen. However, elephant seals breeding at Península Valdes on the mainland of South America and at the Falkland (Malvinas) Islands are thought to be a distinct population from those at South Georgia. Similarly, the elephant seal populations at the Prince Edward Islands and Iles Crozet are also considered to be distinct from those at Iles Kerguelen and Heard Island, and the small populations in the Tristan de Cunha Islands and Gough Island may also be distinct. Additionally, some colonies have unknown affiliations (e.g. Bouvet). Thus, there may be at least five and perhaps more, distinct breeding populations, although their foraging areas overlap quite extensively at sea (SCAR 1991, Reijnders et al. 1993, Bailleaul 2007, Biuw 2007).

The most important southern elephant seal populations in the world have been either stable or decreasing sharply in the last 50 years (Hindell and Burton 1987, Guinet et al. 1992, Pistorius et al. 2004). Today, some of those that were in decline are apparently returning to a positive trend (Boyd et al. 1996, Guinet et al. 1999).The Valdés population has grown and now is stable (Campagna and Lewis 1992, Lewis et al. 1998). The reason for the differences in the trends in various areas is not known with certainty, but different levels of food availability associated with various oceanographic features seems to have played a role.
Population Trend: Unknown

Habitat and Ecology [top]

Habitat and Ecology: The southern elephant seal is the largest pinniped species. Adult males typically reach 4.5 m and a maximum of 5.8 m in length, and weigh 1,500-3,000 kg, with a maximum weight of about 3,700 kg. The literature contains numerous accounts of much larger males, with maximum lengths of 6-7 m, but these dimensions usually include hind flippers, whereas the standard length in use today is from tip of nose to tip of tail. Adult females are similar in size and weight to northern elephant seal females weighing 350-600 kg with exceptionally large females reaching 800 kg. Newborn pups are about 1.3 m and 40-50 kg. Pups are born in a long woolly black lanugo coat that is shed at about 3 weeks of age, to reveal a silver gray counter-shaded coat that is yellowish gray ventrally.

Females reach sexual maturity between 3 and 5 years and males reach sexual maturity at an age of 4 years. However, few males breed until they reach the age of least 10 years (Jones 1981). Ninety percent of males die before the age of 10 years while 90% of females die before the age of 14 years (McCann 1980, Reijnders et al. 1993).

Pregnant females arrive from September to October, and usually give birth within five days of their return. Pups are nursed for an average of 23 days and then are abruptly weaned when the female departs to sea. Females come into estrous about four days before they wean their pup and mate, starting a new reproductive cycle before completing their current effort. Pups remain on the breeding beaches for eight to ten weeks, during which time they complete the moult of their lanugo coat, before departing to sea.

Elephant seals have an annual cycle with two well-defined pelagic phases, with transitions being marked by moult and reproduction. Adult males and females come ashore to reproduce from August to October. This species provide one of the most extreme examples of polygyny among mammals. The social units are harems, each held by a single dominant male that monopolizes access to up to 120-150 sexually receptive females for a period of approximately two months. Early in the breeding season males establish dominance hierarchies on beaches via impressive displays, which include rearing up on the hindquarters and lifting almost two-thirds of the body straight up to fight with a peer or issue vocal challenges to nearby bulls.

Vocalizations include a booming, loud call of the adult male in the breeding season, variously called a bubbling roar, a harsh rattling sound, and a low pitched series of pulses with little variation in frequency. Adult females have a high-pitched yodeling call which they use when distressed, and to call their pups. They will also utter a low pitch, sputtering growl. Pups call to their mothers with a sharp bark or yap, which is also used when interacting with other seals.

Southern elephant seals spend a large percentage of their lives at sea and only return to land to give birth, breed and moult. At sea, they range far from their rookeries and predominantly feed between the Subantarctic convergence and the northern edge of the pack ice, south of the Antarctic convergence. Adult males typically venture further south than females, and are known to forage at the seaward edge of the Antarctic continental shelf.

Foraging elephant seals combine exceptionally deep diving with long-distance traveling, covering millions of square kilometers while traversing a wide range of oceanographic regions during periods of up to seven months at sea. The seals spend most of their at-sea time in particular water masses that include frontal systems, currents and shifting marginal ice-edge zones. Studies of foraging locations suggest that seals are sensitive to fine-scale variation in bathymetry and ocean surface properties (sea-ice concentration, sea surface temperature).

Southern elephant seals are prodigious divers and routinely reach the same depths as their northern counterparts. Dive depth and duration vary during the year and between the sexes, but normally range from 300 to 500 m deep and from 20 to just over 30 minutes in duration. A maximum depth of 1430 m was recorded for a female, following her return to sea after the moult. Another post-moult female dove for an astonishing 120 minutes, which is by far the longest dive ever recorded for a pinniped.

Prey consists of approximately 75% squid and 25% fish. Antarctic Notothenia fishes are thought to be important prey when these seals are near the Antarctic continental shelf. Most feeding by females occurs in deep ocean areas at mid-water depths. Adult males pass through female feeding areas on their way south to Antarctic continental slope and shelf waters, where their diving activity suggests they pursue more benthic prey.

Killer whales, and in lower latitudes, large sharks are predators on this species. Leopard seals are also known to kill southern elephant seals.
Systems: Marine

Threats [top]

Major Threat(s): Southern elephant seals were hunted for thousands of years by aboriginal and native peoples in Australia and South America. More recently, they were subjected to intensive commercial harvests starting in the early 19th century and not ending until 1964 at South Georgia. They were prized for their large quantity of blubber that could be rendered to fine, valuable oil.

There are few threats and conflicts today, as southern elephant seals live far from human population centres and have minimal interactions with commercial fisheries. Intensive fishing could potentially deplete important prey stocks. However, relatively little is known about their feeding habits. There is no evidence that recent declines for animals breeding in the Indian and Pacific Oceans are related to fisheries in the Southern Ocean (SCAR 1991). However, development of new fisheries at high latitudes in the future could have a significant impact on elephant seal populations (SCAR 1991, Reijnders et al. 1993).

In the South Orkney Islands a few young male elephant seals were killed for dog food in the 1950s and early 1960s when they were ashore moulting. Southern elephant seals that haul out at mainland sites could come in contact with feral dogs and other terrestrial carnivores and be exposed to a variety of diseases including morbiliviruses.

The possible effects of global climate change on southern elephant seals are not well known. Learmonth et al. (2006) suggest that while the effects of global climate change are uncertain, that the species is likely to decline as a result of habitat and ecosystem changes.

Conservation Actions [top]

Conservation Actions: Any future exploitation within the Antarctic Treaty area (south of 60ºS) would be regulated by the Convention for the Conservation of Antarctic Seals, while north of this area the Convention on Antarctic Marine Living Resources and various national measures for the islands and continental areas on which the species breeds and occurs apply. The Falkland (Malvinas) Islands Dependencies Conservation Ordinance provides protection for southern elephant seals on South Georgia and the South Sandwich Islands (Reijnders et al. 1993). Listed on CITES Appendix II.

Citation: Campagna, C. (IUCN SSC Pinniped Specialist Group) 2008. Mirounga leonina. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 27 November 2014.
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