Southern elephant seal Temporal range: Pleistocene-recent | |
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Male (bull) | |
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Females (cows) and pups | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Mammalia |
Order: | Carnivora |
Clade: | Pinnipedia |
Family: | Phocidae |
Genus: | Mirounga |
Species: | M. leonina |
Binomial name | |
Mirounga leonina | |
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Southern elephant seal range | |
Synonyms | |
Phoca leoninaLinnaeus, 1758 Contents |
The southern elephant seal (Mirounga leonina) is one of two species of elephant seals. It is the largest member of the clade Pinnipedia and the order Carnivora, as well as the largest extant marine mammal that is not a cetacean. 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. [3] John Edward Gray established the genus Mirounga in 1827. [10]
In the nineteenth century, the species was often called "bottle-nosed seal". [11]
The southern elephant seal is distinguished from the northern elephant seal (which does not overlap in range with this species) by its greater body mass and a shorter proboscis. 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. [12] On average female southern elephant seals weigh 350 to 900 kg (770 to 1,980 lb) and measure 2.6 to 3 m (8.5 to 9.8 ft) long, whereas bulls can range from 1,500 to 3,700 kg (3,300 to 8,200 lb) and grow to 4.2 to 5.8 m (14 to 19 ft) in length. [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. [15]
Southern elephant seal size also varies regionally. Studies have indicated elephant seals from South Georgia are around 30% heavier and 10% longer on average than those from Macquarie Island. [12] The record-sized bull, shot in Possession Bay, South Georgia, on 28 February 1913, measured 6.85 m (22.5 ft) long and was estimated to weigh 5,000 kg (11,000 lb), although it was only partially weighed piecemeal. [9] [16] The maximum size of a female is 1,000 kg (2,200 lb) and 3.7 m (12 ft). [9] [17]
A southern elephant seal's eyes are large, round, and black. The width of the eyes, and a high concentration of low-light pigments, suggest sight plays an important role in the capture of prey. Like all seals, elephant seals have hind limbs whose ends form the tail and tail fin. Each of the "feet" can deploy five long, webbed fingers. This agile dual palm is used to propel water. The pectoral fins are used little while swimming. 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.
Pups are born with fur and are completely black. Their coats are unsuited to water, but protect infants by insulating them from the cold air. The first moulting accompanies weaning. After moulting, the coats may turn grey and brown, depending on the thickness and moisture of hair. Among older males, the skin takes the form of a thick leather which is often scarred.
Like other seals, the vascular system of elephant seals is adapted to the cold; a mixture of small veins surround arteries, capturing heat from them. This structure is present in extremities such as the hind legs.
Southern elephant seal world population was estimated at 650,000 in the mid-1990s, [1] and was estimated in 2005 at between 664,000 and 740,000. [18] Studies have shown the existence of three geographic subpopulations, one in each of the three oceans.
Tracking studies have indicated the routes traveled by elephant seals, demonstrating their main feeding area is at the edge of the Antarctic continent. While elephant seals may come ashore in Antarctica occasionally to rest or to mate, they gather to breed in subantarctic locations.
The largest subpopulation is in the South Atlantic, with more than 400,000 individuals, including about 113,000 breeding females on South Georgia; [19] the other breeding colonies of the Atlantic subpopulation are located on the Falkland Islands and Valdes Peninsula in Argentina (the only continental breeding population).
The second subpopulation, in the south Indian Ocean, consists of up to 200,000 individuals, three-quarters of which breed in the Kerguelen Islands and the rest in the Crozet Islands, Marion and Prince Edward Islands, and Heard Island. Some individuals also breed on Amsterdam Island.
The third subpopulation of about 75,000 seals is found in the subantarctic islands of the Pacific Ocean south of Tasmania and New Zealand, mainly Macquarie Island.
Colonies once existed in Tasmania, Saint Helena, and the Juan Fernández Islands off the coast of Chile. Some individuals at the time of moulting have been found in South Africa, Australia or Uruguay. Lost animals have also been reported from time to time on the shores of Mauritius, with two reports from the Río Guayas estuary area in Ecuador [18] and a beach in Lima, Peru. [20] Reality of the creature so called Manatee of Helena had been pointed out as possible misidentification of elephant seals historically present on Saint Helena. [21]
In Chile, the species is currently believed to be in a process of re-colonization of its former range. [22] [23] It has for example been sighted in the 2010s at the mouth of Toltén River and at the Caicura Islets. [23] [24]
After the end of large-scale seal hunting in the 19th century, the southern elephant seal recovered to a sizable population in the 1950s; since then, an unexplained decline in the subpopulations of the Indian Ocean and Pacific Ocean has occurred. The population now seems to be stable; the reasons for the fluctuation are unknown. 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. [25]
Elephant seals are among the seals that can stay on land for the longest periods of time, as they can stay dry for several consecutive weeks each year. Males arrive in the colonies earlier than the females and fight for control of harems when they arrive. [26] Large body size confers advantages in fighting, and the agonistic relationships of the bulls gives rise to a dominance hierarchy, with access to harems and activity within harems being determined by rank. [27] The dominant bulls ("harem masters") establish harems of several dozen females. The least successful males have no harems, but they may try to copulate with a harem male's females when the male is not looking. The majority of primiparous females and a significant proportion of multiparous females mate at sea with roaming males away from harems. [28]
An elephant seal must stay in his territory to defend it, which could mean months without eating, having to live on his blubber storage. Two fighting males use their weight and canine teeth against each other. The outcome is rarely fatal, and the defeated bull will flee; however, bulls can suffer severe tears and cuts. Some males can stay ashore for more than three months without food. Males commonly vocalize with a coughing roar that serves in both individual recognition and size assessment. [27] Conflicts between high-ranking males are more often resolved with posturing and vocalizing than with physical contact. [27]
Generally, pups are born rather quickly in the breeding season. [29] After being born, a newborn will bark or yap and its mother will respond with a high-pitched moan. [30] The newborn begins to suckle immediately. Lactation lasts an average of 23 days. Throughout this period, the female fasts. Newborns weigh about 40 kg (88 lb) at birth, and reach 120 to 130 kg (260 to 290 lb) by the time they are weaned. The mother loses significant weight during this time. Young weaned seals gather in nurseries until they lose their birth coats. They enter the water to practice swimming, generally starting their apprenticeship in estuaries or ponds. In summer, the elephant seals come ashore to moult. This sometimes happens directly after reproduction.
Satellite tracking revealed the seals spend very little time on the surface, usually a few minutes for breathing. They dive repeatedly, each time for more than 20 minutes, to hunt their prey—squid and fish—at depths of 400 to 1,000 m (1,300 to 3,300 ft). They are the deepest diving air-breathing non-cetaceans and have been recorded at a maximum of 2,388 m (7,835 ft) in depth. [31] [32]
As for the duration, depth and sequence of dives, the southern elephant seal is the best performing seal. In many regards, they exceed even most cetaceans. These capabilities result from nonstandard physiological adaptations, common to marine mammals, but particularly developed in elephant seals. The coping strategy is based on increased oxygen storage and reduced oxygen consumption.
In the ocean, the seals apparently live alone. Most females dive in pelagic zones for foraging, while males dive in both pelagic and benthic zones. [33] Individuals will return annually to the same hunting areas. 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. [34]
While hunting in the dark depths, elephant seals seem to locate their prey, at least in part, using vision; the bioluminescence of some prey animals can facilitate their capture. 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. and Gymnoscopelus spp.), nothothens (i.e. Genera Lepidonotothen, Pleuragramma, Trematomus, Pagothenia,), Channichthyidsae spp., Bathylagidae spp., [37] krill (mostly Euphausia spp.) and other crustaceans, and even algae. [38]
Weaned pups and juveniles may fall prey to orcas. [39] Cases where weaned pups have been attacked and killed by leopard seals (Hydrurga leptonyx) and New Zealand sea lions (Phocarctos hookeri), exclusively small pups in the latter case, have been recorded. Great white sharks (Carcharodon carcharias) have hunted elephant seals near Campbell Island, while bite marks from a southern sleeper shark (Somniosus antarcticus) have been found on surviving elephant seals in the Macquarie Islands. [40] [41]
After their near extinction due to hunting in the 19th century, the total population was estimated at between 664,000 and 740,000 in 2005, [18] but as of 2002, two of the three major subpopulations were declining. [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. [42] Most of their important breeding sites are now protected by international treaty, as UNESCO World Heritage Sites, or by national legislation.
Climate change likely has a wide-ranging and diverse impact on marine species such as southern elephant seals. As top predators in the Southern Ocean, southern elephant seals inhabit one of the most sensitive and vulnerable regions to rapid climate change. Global efforts such as the Southern elephant seals as oceanographic samplers [43] and the Marine Mammals Exploring the Oceans Pole to Pole projects [44] have led to the collection of a large suite of long-term coupled behavioural-oceanographic data. As part of these projects, satellite-relay data loggers were attached to southern elephant seals to collect physical and biological data. 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. This data provides information on how the Southern Ocean is changing in relation to climate change as well as how these species respond to changes. [45] [46]
These projects focused on southern elephant seals because they are deep divers as well as a major predator in the Southern Ocean in terms of their population size and food consumption. As predators of the upper levels of the food-web, their foraging success and population dynamics impart valuable information about productivity at different trophic levels. [47] The well-being of southern elephant seals therefore mirrors that of the whole Antarctic ecosystem.
Southern elephant seals from different colonies frequent specific oceanographic regions to forage. They feed most successfully in areas with specific hydrographic properties, e.g. the upwelling regions of Circumpolar Deep Water within the Antarctic Circumpolar Current. [48] In the Southern Ocean, southern elephant seals associate more frequently with southerly, higher‐latitude fronts and frontal zones. However, the foraging success in association with these regions varies strongly according to year, season and sex. Some of the seasonal and interannual variations in foraging success can be linked to climatic changes such as positional shifts in fronts and variability associated with frontal positions. [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. [50] Minazo became popular for his signature bucket-holding, tongue-lolling pose. In 2006, Minazo was memorialized by the Japanese noise musician Masami Akita, also known as Merzbow, in a two-volume album, [51] [52] with artwork by Jenny Akita showing Minazo holding his beloved bucket. In 2007, Minazo became the subject of an image macro similar to lolcat called "lolrus". 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. [50] Minazo has also been featured on several T-shirt designs.
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. His repeated interactions with humans have caused concern for Neil's welfare as well as potential risks to the public. [53] [54]
The earless seals, phocids, or true seals are one of the three main groups of mammals within the seal lineage, Pinnipedia. All true seals are members of the family Phocidae. They are sometimes called crawling seals to distinguish them from the fur seals and sea lions of the family Otariidae. Seals live in the oceans of both hemispheres and, with the exception of the more tropical monk seals, are mostly confined to polar, subpolar, and temperate climates. The Baikal seal is the only species of exclusively freshwater seal.
Fur seals are any of nine species of pinnipeds belonging to the subfamily Arctocephalinae in the family Otariidae. They are much more closely related to sea lions than true seals, and share with them external ears (pinnae), relatively long and muscular foreflippers, and the ability to walk on all fours. They are marked by their dense underfur, which made them a long-time object of commercial hunting. Eight species belong to the genus Arctocephalus and are found primarily in the Southern Hemisphere, while a ninth species also sometimes called fur seal, the Northern fur seal, belongs to a different genus and inhabits the North Pacific. The fur seals in Arctocephalus are more closely related to sea lions than they are to the Northern fur seal, but all three groups are more closely related to one another than they are to true seals.
Pinnipeds, commonly known as seals, are a widely distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant families Odobenidae, Otariidae, and Phocidae, with 34 extant species and more than 50 extinct species described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular evidence supports them as a monophyletic group. Pinnipeds belong to the suborder Caniformia of the order Carnivora; their closest living relatives are musteloids, having diverged about 50 million years ago.
The spectacled porpoise is a small to midsize porpoise indigenous to the Southern Ocean. It is one of the most poorly studied cetaceans, partly due to its remote range in the Southern Ocean. What little is known about this porpoise species has been gathered mainly from stranded individuals, and a few observations of living animals made at sea.
The dusky dolphin is a dolphin found in coastal waters in the Southern Hemisphere. Its specific epithet is Latin for "dark" or "dim". It is very closely genetically related to the Pacific white-sided dolphin, but current scientific consensus holds they are distinct species. The dolphin's range is patchy, with major populations around South America, southwestern Africa, New Zealand, and various oceanic islands, with some sightings around southern Australia and Tasmania. The dusky dolphin prefers cool currents and inshore waters, but can also be found offshore. It feeds on a variety of fish and squid species and has flexible hunting tactics. The dusky dolphin is known for its remarkable acrobatics, having a number of aerial behaviours. The status of the dolphin is unknown, but it has been commonly caught in gill nets.
The grey seal is a large seal of the family Phocidae, which are commonly referred to as "true seals" or "earless seals". The only species classified in the genus Halichoerus, it is found on both shores of the North Atlantic Ocean. In Latin, Halichoerus grypus means "hook-nosed sea pig". Its name is spelled gray seal in the United States; it is also known as Atlantic seal and the horsehead seal.
The leopard seal, also referred to as the sea leopard, is the second largest species of seal in the Antarctic. Its only natural predator is the orca. It feeds on a wide range of prey including cephalopods, other pinnipeds, krill, fish, and birds, particularly penguins. It is the only species in the genus Hydrurga. Its closest relatives are the Ross seal, the crabeater seal and the Weddell seal, which together are known as the tribe of Lobodontini seals. The name hydrurga means "water worker" and leptonyx is the Greek for "thin-clawed".
The northern elephant seal is one of two species of elephant seal. It is a member of the family Phocidae. Elephant seals derive their name from their great size and from the male's large proboscis, which is used in making extraordinarily loud roaring noises, especially during the mating competition. Sexual dimorphism in size is great. Correspondingly, the mating system is highly polygynous; a successful male is able to impregnate up to 50 females in one season.
Elephant seals or sea elephants are very large, oceangoing earless seals in the genus Mirounga. Both species, the northern elephant seal and the southern elephant seal, were hunted to the brink of extinction for oil by the end of the 19th century, but their numbers have since recovered. They can weigh up to 4,000 kilograms (8,800 lb). Despite their name, elephant seals are not closely related to elephants, and the large proboscis or trunk that males have was convergently evolved.
Monk seals are earless seals of the tribe Monachini. They are the only earless seals found in tropical climates. The two genera of monk seals, Monachus and Neomonachus, comprise three species: the Mediterranean monk seal, Monachus monachus; the Hawaiian monk seal, Neomonachus schauinslandi; and the Caribbean monk seal, Neomonachus tropicalis, which became extinct in the 20th century. The two surviving species are now rare and in imminent danger of extinction. All three monk seal species were classified in genus Monachus until 2014, when the Caribbean and Hawaiian species were placed into a new genus, Neomonachus.
The northern fur seal is an eared seal found along the north Pacific Ocean, the Bering Sea, and the Sea of Okhotsk. It is the largest member of the fur seal subfamily (Arctocephalinae) and the only living species in the genus Callorhinus. A single fossil species, Callorhinus gilmorei, is known from the Pliocene of Japan and western North America.
The Antarctic fur seal is one of eight seals in the genus Arctocephalus, and one of nine fur seals in the subfamily Arctocephalinae. Despite what its name suggests, the Antarctic fur seal is mostly distributed in Subantarctic islands and its scientific name is thought to have come from the German vessel SMS Gazelle, which was the first to collect specimens of this species from Kerguelen Islands.
The subantarctic fur seal is a species of arctocephaline found in the southern parts of the Indian, Pacific, and Atlantic Oceans. It was first described by Gray in 1872 from a specimen recovered in northern Australia—hence the inappropriate specific name tropicalis.
The South American sea lion, also called the southern sea lion and the Patagonian sea lion, is a sea lion found on the western and southeastern coasts of South America. It is the only member of the genus Otaria. The species is highly sexually dimorphic. Males have a large head and prominent mane. They mainly feed on fish and cephalopods and haul out on sand, gravel, rocky, or pebble beaches. In most populations, breeding males are both territorial and harem holding; they establish territories first and then try to herd females into them. The overall population of the species is considered stable, estimated at 265,000 animals.
Arctocephalus forsteri is a species of fur seal found mainly around southern Australia and New Zealand. The name New Zealand fur seal is used by English speakers in New Zealand; kekeno is used in the Māori language. As of 2014, the common name long-nosed fur seal has been proposed for the population of seals inhabiting Australia.
The true seal tribe Lobodontini, collectively known as the Antarctic seals or lobodontin seals, consist of four species of seals in four genera: the crabeater seal, the leopard seal, the Weddell seal, and the Ross seal. All lobodontine seals have circumpolar distributions surrounding Antarctica. They include both the world's most abundant seal and the only predominantly mammal-eating seal. While the Weddell seal prefers the shore-fast ice, the other species live primarily on and around the off-shore pack ice. Thus, though they are collectively the most abundant group of seals in the world, the combination of remote range and inaccessible habitat make them among the least well studied of the world's seals.
Galiteuthis glacialis is a species of glass squid from the Antarctic Convergence. It is in the family Cranchiidae and subfamily Taoniinae. They are endemic to the Antarctic and are found in the Southern Ocean, around the Weddell Sea and the South Shetland Islands. Galiteuthis glacialis are one of the most plentiful and widely dispersed species of Antarctic squid. These squids are found in the mesopelagic and bathypelagic layers of the open ocean and demonstrate vertical migration. They can reach a maximum mantle length of 500 mm (0.5m).
Sexual selection in mammals is a process the study of which started with Charles Darwin's observations concerning sexual selection, including sexual selection in humans, and in other mammals, consisting of male–male competition and mate choice that mold the development of future phenotypes in a population for a given species.
Randall William Davis is an American educator and researcher who studies the physiology and behavioral ecology of marine mammals and other aquatic vertebrates. His physiological research focuses on adaptations of marine mammals for deep, prolonged diving. Davis has continually emphasized the importance of studying aquatic animals in their natural environment and has spent many years developing animal-borne instruments that record video and monitor three-dimensional movements, swimming performance and environmental variables to better understand their behavior and ecology. His academic endeavors and 94 research expeditions have taken him to 64 countries and territories on seven continents and all of the world's oceans.
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