Southern Elephant Seal
Encyclopedia
The Southern Elephant Seal (Mirounga leonina) is one of the two extant species
of elephant seal
. It is both the most massive pinniped
and member of the order Carnivora
living today. The seal gets its name from its great size and the large proboscis
of the adult males, which is used to make extraordinarily loud roaring noises, especially during the mating season.
(which doesn't overlap in range with this species) by its greater body mass and a wider proboscis. This seals' size shows extreme sexual dimorphism
, possibly the largest of any mammal, with the males typically five to six times heavier than the females.
While the females average 400 to 900 kg (881.8 to 1,984.2 lb) and 2.6 to 3 m (8.5 to 9.8 ft) long, the bulls average 2200 to 4000 kg (4,850.2 to 8,818.5 lb) and 4.2 to 5 m (13.8 to 16.4 ft) long.
The record-sized bull, shot in Possession Bay, South Georgia
on February 28, 1913, measured 6.85 metres (22.5 ft) long and was estimated to weigh 5000 kilograms (11,023.1 lb). The maximum size of a female is 1000 kilograms (2,204.6 lb) and 3.7 metres (12.1 ft).
The eyes are large, round and black. The width of the eyes, and a high concentration of low light pigments, suggest that 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 the 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 kilometres per hour or 5 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 coat is unsuited to water, but protects 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.
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 that 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 approximately 113,000 breeding females on South Georgia;
the other breeding colonies are located on the Falkland Islands
and Valdes Peninsula
in Argentina
(the only continental breeding population).
The second subpopulation, in the south Indian Ocean
, consist 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 sub-population 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
. Sometimes individuals at the time of moulting have been found in South Africa
or Australia
. There have also been reports from time to time of animals lost on the shores of Mauritius
. There are two reports from the Río Guayas estuary area in Ecuador
.
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, there has been an unexplained decline in the subpopulations of the Indian Ocean and Pacific Ocean. 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.
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. 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. The dominant bulls or “harem masters” establish harems of several dozen females. The least successful males have no harems, but may try to copulate a harem male's females when the male is not looking.
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. Conflicts between high ranking males are more often resolved with posturing and vocalizing than with physical contact.
Generally, the pups are born rather quickly in the breeding season. The newborn begins to suckle immediately. Lactation lasts an average of 23 days. Throughout this period, the female fasts. Newborns weigh about 40 kilograms (88.2 lb) at birth, and reach 120 to 130 kg (264.6 to 286.6 lb) by the time they are weaned. The mother loses significant weight during this time.
Young seals that are weaned gather in nurseries until they lose their birth coat. 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.
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Satellite tracking revealed that the seals spend very little time on the surface—usually a few minutes for oxygen. They dive repeatedly, each time for more than twenty minutes, to hunt their prey—squid
and fish
— at depths of 400 to 1000 m (1,312.3 to 3,280.8 ft). The documented diving records for the seals are nearly two hours for the duration, and more than 1400 metres (4,593.2 ft) in depth.
.jpg)
As far as duration, depth, and the sequence of dives, the Southern elephant seal is the best performing seal. In many regards, they exceed even most cetaceans. These capabilities result from non-standard physiological adaptations, common to marine mammals but particularly developed in elephant seals. The coping strategy is based on two pillars: increasing the storage of oxygen and reducing its consumption.
In the ocean, the seals apparently live alone. Most females mostly do only pelagic
foraging' dives, while males do both pelagic and benthic
foraging dives. Individuals will return annually to the same hunting areas.
While hunting in the dark depths, it is partly thanks to the use of vision that the elephant seals seem to locate their prey; 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 it is assumed that their vibrissae
, which are sensitive to vibrations, play a role in search of food. When at the subantarctic or Antarctic coasts, the seals can also consume shellfish, nothothens
, lanternfish
, krill
, cephalopod
s or even algae
. Weaned pups may be predated by orca
s and (rarely) by leopard seal
s, while juveniles may also fall prey to orcas.
After their near extinction due to hunting in the 19th century, the total population was estimated at between 664,000 and 740,000 animals in 2005, but as of 2002 two of the three major populations were declining. The reasons for this are unclear, but are thought to be related to the maldistribution and declining levels of the seal's primary food sources. Most of their most important breeding sites are now protected by international treaty, as UNESCO World Heritage Sites, or by national legislation.
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
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 suggests that 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. Minazo has also featured on several t-shirt designs.
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
of elephant seal
Elephant seal
Elephant seals are large, oceangoing seals in the genus Mirounga. There are two species: the northern elephant seal and the southern elephant seal . Both were hunted to the brink of extinction by the end of the 19th century, but numbers have since recovered...
. It is both the most massive pinniped
Pinniped
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae , Otariidae , and Phocidae .-Overview: Pinnipeds are typically sleek-bodied and barrel-shaped...
and member of the order Carnivora
Carnivora
The diverse order Carnivora |Latin]] carō "flesh", + vorāre "to devour") includes over 260 species of placental mammals. Its members are formally referred to as carnivorans, while the word "carnivore" can refer to any meat-eating animal...
living today. The seal gets its name from its great size and the large proboscis
Proboscis
A proboscis is an elongated appendage from the head of an animal, either a vertebrate or an invertebrate. In simpler terms, a proboscis is the straw-like mouth found in several varieties of species.-Etymology:...
of the adult males, which is used to make extraordinarily loud roaring noises, especially during the mating season.
Description
The Southern Elephant Seal is distinguished from the Northern Elephant SealNorthern Elephant Seal
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...
(which doesn't overlap in range with this species) by its greater body mass and a wider proboscis. This seals' size shows extreme sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
, possibly the largest of any mammal, with the males typically five to six times heavier than the females.
While the females average 400 to 900 kg (881.8 to 1,984.2 lb) and 2.6 to 3 m (8.5 to 9.8 ft) long, the bulls average 2200 to 4000 kg (4,850.2 to 8,818.5 lb) and 4.2 to 5 m (13.8 to 16.4 ft) long.
The record-sized bull, shot in Possession Bay, South Georgia
South Georgia and the South Sandwich Islands
South Georgia and the South Sandwich Islands is a British overseas territory and overseas territory of the European Union in the southern Atlantic Ocean. It is a remote and inhospitable collection of islands, consisting of South Georgia and a chain of smaller islands, known as the South Sandwich...
on February 28, 1913, measured 6.85 metres (22.5 ft) long and was estimated to weigh 5000 kilograms (11,023.1 lb). The maximum size of a female is 1000 kilograms (2,204.6 lb) and 3.7 metres (12.1 ft).
The eyes are large, round and black. The width of the eyes, and a high concentration of low light pigments, suggest that 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 the 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 kilometres per hour or 5 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 coat is unsuited to water, but protects 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.
Range and population
The world population was estimated at 650,000 animals in the mid-1990s, and was estimated in 2005 at between 664,000 and 740,000 animals.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 that 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
Subantarctic
The Subantarctic is a region in the southern hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° – 60° south of the Equator. The subantarctic region includes many islands in the southern parts of the Indian Ocean, Atlantic Ocean and...
locations.
the other breeding colonies are located on the Falkland Islands
Falkland Islands
The Falkland Islands are an archipelago in the South Atlantic Ocean, located about from the coast of mainland South America. The archipelago consists of East Falkland, West Falkland and 776 lesser islands. The capital, Stanley, is on East Falkland...
and Valdes Peninsula
Valdes Peninsula
The Valdes Peninsula is a peninsula on the Atlantic coast in the Viedma Department in the north east of Chubut Province, Argentina. About in size, it is an important nature reserve which was listed as a World Heritage Site by UNESCO in 1999.- Geography :The nearest large town is Puerto Madryn...
in Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
(the only continental breeding population).
The second subpopulation, in the south Indian Ocean
Indian Ocean
The Indian Ocean is the third largest of the world's oceanic divisions, covering approximately 20% of the water on the Earth's surface. It is bounded on the north by the Indian Subcontinent and Arabian Peninsula ; on the west by eastern Africa; on the east by Indochina, the Sunda Islands, and...
, consist of up to 200,000 individuals, three-quarters of which breed in the Kerguelen Islands
Kerguelen Islands
The Kerguelen Islands , also known as the Desolation Islands, are a group of islands in the southern Indian Ocean constituting the emerged part of the otherwise submerged Kerguelen Plateau. The islands, along with Adélie Land, the Crozet Islands and the Amsterdam and Saint Paul Islands are part of...
and the rest in the Crozet Islands
Crozet Islands
The Crozet Islands are a sub-antarctic archipelago of small islands in the southern Indian Ocean. They form one of the five administrative districts of the French Southern and Antarctic Lands.-Geography:...
, Marion and Prince Edward Islands
Prince Edward Islands
The Prince Edward Islands are two small islands in the sub-antarctic Indian Ocean that are part of South Africa. The islands, named Marion Island and Prince Edward Island, are located at ....
, and Heard Island
Heard Island and McDonald Islands
The Heard Island and McDonald Islands are an Australian external territory and volcanic group of barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall size is in area and it has of coastline...
. Some individuals also breed on Amsterdam Island
Île Amsterdam
New Amsterdam, Amsterdam Island, or Île Amsterdam is a French island in the Indian Ocean located at . It is part of the French Southern and Antarctic Lands.- History :...
.
Subantarctic
The Subantarctic is a region in the southern hemisphere, located immediately north of the Antarctic region. This translates roughly to a latitude of between 46° – 60° south of the Equator. The subantarctic region includes many islands in the southern parts of the Indian Ocean, Atlantic Ocean and...
islands of the Pacific Ocean south of Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
and New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
, mainly Macquarie Island
Macquarie Island
Macquarie Island lies in the southwest corner of the Pacific Ocean, about half-way between New Zealand and Antarctica, at 54°30S, 158°57E. Politically, it has formed part of the Australian state of Tasmania since 1900 and became a Tasmanian State Reserve in 1978. In 1997 it became a world heritage...
.
Colonies once existed in Tasmania
Tasmania
Tasmania is an Australian island and state. It is south of the continent, separated by Bass Strait. The state includes the island of Tasmania—the 26th largest island in the world—and the surrounding islands. The state has a population of 507,626 , of whom almost half reside in the greater Hobart...
, Saint Helena
Saint Helena
Saint Helena , named after St Helena of Constantinople, is an island of volcanic origin in the South Atlantic Ocean. It is part of the British overseas territory of Saint Helena, Ascension and Tristan da Cunha which also includes Ascension Island and the islands of Tristan da Cunha...
, and the Juan Fernández Islands
Juan Fernández Islands
The Juan Fernández Islands are a sparsely inhabited island group reliant on tourism and fishing in the South Pacific Ocean, situated about off the coast of Chile, and is composed of three main volcanic islands; Robinson Crusoe Island, Alejandro Selkirk Island and Santa Clara Island, the first...
off the coast of Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
. Sometimes individuals at the time of moulting have been found in South Africa
South Africa
The Republic of South Africa is a country in southern Africa. Located at the southern tip of Africa, it is divided into nine provinces, with of coastline on the Atlantic and Indian oceans...
or Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
. There have also been reports from time to time of animals lost on the shores of Mauritius
Mauritius
Mauritius , officially the Republic of Mauritius is an island nation off the southeast coast of the African continent in the southwest Indian Ocean, about east of Madagascar...
. There are two reports from the Río Guayas estuary area in Ecuador
Ecuador
Ecuador , officially the Republic of Ecuador is a representative democratic republic in South America, bordered by Colombia on the north, Peru on the east and south, and by the Pacific Ocean to the west. It is one of only two countries in South America, along with Chile, that do not have a border...
.
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, there has been an unexplained decline in the subpopulations of the Indian Ocean and Pacific Ocean. 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.
Social behavior and reproduction
Generally, the pups are born rather quickly in the breeding season. The newborn begins to suckle immediately. Lactation lasts an average of 23 days. Throughout this period, the female fasts. Newborns weigh about 40 kilograms (88.2 lb) at birth, and reach 120 to 130 kg (264.6 to 286.6 lb) by the time they are weaned. The mother loses significant weight during this time.
Young seals that are weaned gather in nurseries until they lose their birth coat. 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.
Feeding and diving
Squid
Squid are cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two, usually longer, tentacles...
and fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...
— at depths of 400 to 1000 m (1,312.3 to 3,280.8 ft). The documented diving records for the seals are nearly two hours for the duration, and more than 1400 metres (4,593.2 ft) in depth.
In the ocean, the seals apparently live alone. Most females mostly do only pelagic
Pelagic zone
Any water in a sea or lake that is not close to the bottom or near to the shore can be said to be in the pelagic zone. The word pelagic comes from the Greek πέλαγος or pélagos, which means "open sea". The pelagic zone can be thought of in terms of an imaginary cylinder or water column that goes...
foraging' dives, while males do both pelagic and benthic
Benthic zone
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean or a lake, including the sediment surface and some sub-surface layers. Organisms living in this zone are called benthos. They generally live in close relationship with the substrate bottom; many such...
foraging dives. Individuals will return annually to the same hunting areas.
While hunting in the dark depths, it is partly thanks to the use of vision that the elephant seals seem to locate their prey; the bioluminescence
Bioluminescence
Bioluminescence is the production and emission of light by a living organism. Its name is a hybrid word, originating from the Greek bios for "living" and the Latin lumen "light". Bioluminescence is a naturally occurring form of chemiluminescence where energy is released by a chemical reaction in...
of some prey animals can facilitate their capture. Elephant seals do not have a developed system of echolocation
Animal echolocation
Echolocation, also called biosonar, is the biological sonar used by several kinds of animals.Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects...
in the manner of cetaceans, but it is assumed that their vibrissae
Vibrissae
Vibrissae , or whiskers, are specialized hairs usually employed for tactile sensation. The term may also refer to the thick hairs found inside human nostrils, but these have no sensorial function and only operate as an airborne particulate barrier...
, which are sensitive to vibrations, play a role in search of food. When at the subantarctic or Antarctic coasts, the seals can also consume shellfish, nothothens
Nototheniidae
The cod icefishes or nothothens are the family Nototheniidae of acanthopterygian fishes, containing about 50 species in 13 genera. They are traditionally placed in the perciform assemblage together with their relatives, but like every lineage in the "Perciformes" their actual relationships are not...
, lanternfish
Lanternfish
Cooper Lanternfishes are small mesopelagic fish of the large family Myctophidae. One of two families in the order Myctophiformes, the Myctophidae are represented by 246 species in 33 genera, and are found in oceans worldwide. They are aptly named after their conspicuous use of bioluminescence...
, krill
Krill
Krill is the common name given to the order Euphausiacea of shrimp-like marine crustaceans. Also known as euphausiids, these small invertebrates are found in all oceans of the world...
, cephalopod
Cephalopod
A cephalopod is any member of the molluscan class Cephalopoda . These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot...
s or even algae
Algae
Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms, such as the giant kelps that grow to 65 meters in length. They are photosynthetic like plants, and "simple" because their tissues are not organized into the many...
. Weaned pups may be predated by orca
Orca
The killer whale , commonly referred to as the orca, and less commonly as the blackfish, is a toothed whale belonging to the oceanic dolphin family. Killer whales are found in all oceans, from the frigid Arctic and Antarctic regions to tropical seas...
s and (rarely) by leopard seal
Leopard Seal
The leopard seal , also referred to as the sea leopard, is the second largest species of seal in the Antarctic...
s, while juveniles may also fall prey to orcas.
Conservation
Minazo
One of the most famous southern elephant seals is Minazo, who lived in Japan's Enoshima Aquarium from when he was a half-year old until his death in 2005.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
Merzbow
is the main recording name of the Japanese noise musician , born in 1956. Since 1979 he has released in excess of 350 recordings.The name "Merzbow" comes from German artist Kurt Schwitters' artwork, "Merzbau”. This was chosen to reflect Akita's dada influence and junk art aesthetic...
, in a two-volume album
with artwork by Jenny Akita showing Minazo holding his beloved bucket.
In 2007, Minazo became the subject of an image macro
Image macro
In Internet culture, an image macro is a picture captioned with superimposed text for humorous effect.-Internet forums:On Internet forums and imageboards, image macros are used to emphasize a certain phrase by superimposing it over a related picture.-Formats:Although they come in many forms, the...
similar to lolcat
Lolcat
A lolcat is an image combining a photograph of a cat with text intended to contribute humour. The text is often idiosyncratic and grammatically incorrect, and its use in this way is known as "lolspeak" or "kitty pidgin"....
called lolrus. In his liner notes, Masami Akita suggests that 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. Minazo has also featured on several t-shirt designs.