Southern elephant seal
| Southern elephant seal | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Southern elephant seal, bull |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Mirounga Leonina | ||||||||||||
| ( Linnaeus , 1758) |
The southern elephant seal ( Mirounga leonina ) is one of the two species of elephant seal . It is the largest species of seal and at the same time the largest representative of the order carnivores (Carnivora) . Older reports, the credibility of which are questionable, mentioned bulls nine meters long and weighing five tons. Six and a half meters and three and a half tons are confirmed. The trunk is only 10 cm long, compared to the northern elephant seal ( Mirounga angustirostris) significantly smaller. With a maximum length of three meters and a weight of 600 to 800 kilograms, females only achieve much smaller body shapes.
The large colonies of the southern species are located on several islands that are in a ring around Antarctica . Outside the mating season, wandering individuals can also be found on the coasts of South Africa, Australia, New Zealand, Patagonia and Antarctica . Individual animals cover distances of up to 4800 km.
features
The bulls of the southern elephant seal are the largest of the seals. They reach a length of up to over 6 meters with a weight of up to over 4000 kilograms. The animals have their maximum weight when they arrive at the colony in late autumn, after having spent most of the summer and autumn foraging for food. With a body length of up to 4 meters and an average weight of 800 kilograms, the females are significantly smaller than the males. The weight can fluctuate greatly and after birth, the females can within the lactation of about 25 days, half lose their weight.
The males have a large, inflatable trunk , which mainly serves as a sound amplifier during communication and as a sign of dominance over other males. The southern species differs from the northern elephant seal in that it is slightly larger and the sex differences are more extreme; the trunk of the male, however, is relatively smaller than that of the northern elephant seal and protrudes only about 10 centimeters above the mouth.
In terms of physique, the elephant seals correspond to the typical dog seal with short forelegs that have been converted into fins, which are primarily used for stabilization when swimming, and strong hind fins that ensure the animals propulsion in the water. The body is covered by a coat of short and hard hair, which after the coat change has a dark brown to dark gray color with a lighter belly side and fades over the year.
distribution and habitat
The southern elephant seal is circumpolar in the Antarctic and spends most of its life in the sea. It occurs mainly in the areas and islands north of the pack ice regions , but sometimes also lives directly on the coast of Antarctica. Outside the mating season, wandering individuals are also found on the coasts of South Africa, Australia, New Zealand and Patagonia.
During the litter and mating season, it forms colonies on land in which a large number of the animals collect. The largest colonies are found on the island of South Georgia in the South Atlantic, others on Macquarie Island, Heard Island , the Kerguelen and the Valdés Peninsula in southeast Argentina . On the continent of Antarctica, they occur regularly in the Vestfold Mountains area .
Way of life
The southern elephant seal, like the northern species, spends most of its life in the sea, only occasionally appearing on the sea surface to take a breath .
nutrition
Like the northern elephant seal, the southern species only eats food outside of the mating and whelping season. She hunts her prey in the sea. This consists mainly of octopus , crustaceans , bony fish and cartilaginous fish such as bottom-dwelling sharks and rays .
Reproduction
The mating of the southern elephant seals and their birth take place in large colonies on land. These are formed during the mating season in August to November of the year. The males reach these colonies a few weeks before the females and determine their territories. This leads to demonstrations of power and rivalry between the bulls, in which the most dominant bulls occupy the central and largest territories, while the inferior bulls are pushed to the edge of the colonies. When the females arrive, depending on their position on the beach, they are claimed by the respective alpha males and defended against intruders, with individual males leading harems with up to 60 females and mating with them. The females have no control over whose harem they are in; often single females change harem randomly when moving on the beach.
The females who reach the beach pregnant from last year give birth to their young within the first five to seven days after arriving in the colonies. They each give birth to a young animal that is suckled for about 23 days and then left to its own devices. Rare twin births usually lead to the weaker of the two young animals dying shortly after birth. During the breastfeeding period, the mother animal does not eat any food and accordingly quickly becomes lighter and weaker.
At the end of the lactation period in October, the females are ready to mate. When a bull wants to mate with a female, it places one of its pectoral fins over it, grabs it with its teeth in the neck and begins mating . The actual gestation period of the females is about 8 months, so the delayed implantation of the fertilized egg in the uterus takes about three months. Immediately after mating, the young animal is weaned and the adult elephant seals leave the colony again, while the young animals remain on land for some time and then swim into the sea.
The females reach sexual maturity after about 3 years and take part in the annual reproductive cycle after about 6 years. The males only become sexually mature after 5 or 6 years, but can usually only successfully mate after 10 to 12 years. The average maximum age of the males is about 14 years, that of the females about 21 years.
Predators and parasites
One of the few predators of the adult southern elephant seals is the killer whale ( Orcinus orca ), which can inflict severe wounds even on large bulls. There are also large species of shark, especially the great white shark ( Carcharodon carcharias ). The leopard seal ( Hydrurga leptonyx ) primarily hunts smaller seals, including the young elephant seals.
The parasites that appear on southern elephant seals include the animal louse Lepidophthirus macrorhini , which attaches itself to the area of the rear fins. The scratch worm Corynosoma bullosum and the nematode Pseudomonas Terranova decipiens were in intestinal elephant lake found the. The larvae of both species live in Antarctic cod as hosts , which serve as food for the elephant seals.
Older animals can also be colonized by sessile mussel crabs, which only colonize the surface.
The bacterium Jeotgalicoccus pinnipedialis , which occurs there as a natural component, was isolated from the oral flora of the southern elephant seal .
Fossil History and Evolution
There are two theories about the origin of the two species of elephant seals, according to which either the northern species is regarded as a descendant of the southern or the southern species is regarded as a descendant of the northern one. According to an older theory, the northern elephant seals originated from a group of southern elephant seals that migrated to the North Pacific during the Pleistocene and became separated from the original population after the warming of the equatorial regions. Alternatively, it is believed that the origin of the elephant seals lies in the more northern tropical areas of the Pacific and from there a group split off and migrated south, where the southern elephant seal emerged. The last view is considered to be more probable and it is assumed that the family group around the elephant seals and the fossil genus Callophoca originated in the Miocene in the area of today's Caribbean and the ancestors of the elephant seals through the not yet closed gap between the north - and South America reached the Pacific in the early Pliocene . As a result of the cooling of the equatorial areas in the Pleistocene, the populations of the later northern and southern elephant seals separated and were genetically isolated accordingly. The oldest fossil finds of the northern elephant seal come from the late Pleistocene from southern California, fossil finds of the southern species are known from South Africa and the north of Chile .
Taxonomy and systematics
|
Phylogenetic system of dog seals according to Higdon et al. 2007
|
The northern elephant seal was described scientifically for the first time in 1758 by Carl von Linné in the 10th edition of his Systema Naturae under the scientific name Phoca leonina , and was accordingly already known. Juan Ignacio Molina renamed this species to Phoca elephantina in 1782 and the naturalists François Péron , Juan Ignacio Molina, Anselme Gaëtan Desmarest and Henri Marie Ducrotay de Blainville described further species as Phoca proboscidea , Phoca resima , Phoca coxii , Phoca ansonii and Phoca ansonina and until 1820 different islands in the Antarctic, which were later summarized and synonymous with one species . In 1825, John Edward Gray first set up the genus Macrorhinus , which was invalid due to the similarity of names with a beetle genus, and later the genus Mirounga for the Phoca proboscidea described by Péron in 1816 . In the following years further new descriptions and different name combinations of the described species and generic names were added, the first use of the scientific name Mirounga leonina , which is valid today , was in 1905 by Joel Asaph Allen .
Together with the northern elephant seal, the southern elephant seal forms the genus Mirounga , which is assigned to the dog seals . The position within the dog seals is unclear and has been discussed regularly. In 1983 King put forward the theory that is still often cited today that the elephant seals are most closely related to the monk seals ( Monachus ) and that both were particularly original representatives of the dog seals . On the other hand, Bininda-Emonds and Russell could not find any evidence of such a close relationship in 1996, but confirmed the basic position of the elephant seals in the dog seal system. Based on molecular biological results from the year 2007, the elephant seals are currently a sister group of the Lobodontini combined species group from Ross Seal ( Ommatophoca rossii ), Crabeater ( Lobodon carcinophaga ), leopard seals ( Hydrurga leptonyx ) and Weddell ( Leptonychotes weddellii considered) , The monk seals are considered to be a sister group of both taxa, elephant seals and lobodontini.
The generic name Mirounga is derived from "miouroung", the name for southern elephant seals in a language of the Australian Aborigines. The species name leonina is derived from the Latin word "leoninus" for "similar to the lion".
Threat and protection
The species was also heavily persecuted in the 19th century, but never as threatened as the northern elephant seal. There were once colonies on Tasmania , King Island , the Juan Fernández Islands and St. Helena , but here the elephant seals were exterminated by human hunters. A total of about 750,000 individuals live today, more than half of which are found in South Georgia .
Due to the large distribution area and the current lack of serious threats, the International Union for Conservation of Nature and Natural Resources (IUCN) classifies the species as “Least Concern”.
Individual evidence
- ↑ a b c d e f g h i j k Derek Block, Philip Meyer: Mirounga leonina in the Animal Diversity Net.
- ↑ a b c Mirounga leonina in the Red List of Threatened Species of the IUCN 2011.2. Posted by: C. Campagna (IUCN SSC Pinniped Specialist Group), 2008. Retrieved April 13, 2012.
- ↑ a b c d e J.K. Ling, MM Bryden: Mirounga leonina . In: Mammalian Species . tape 391 , 1992, pp. 1–8 ( full text (PDF; 1.1 MB)).
- ↑ L. Hoyles, MD Collins et al. a .: Jeotgalicoccus pinnipedialis sp. nov., from a southern elephant seal (Mirounga leonina). In: International journal of systematic and evolutionary microbiology. Volume 54, No. 3, May 2004, pp. 745-748, doi : 10.1099 / ijs.0.02833-0 . ISSN 1466-5026 . PMID 15143018 .
- ↑ JL Davies: The Pinnipedia: An Essay in Zoogeography. Geographical Review 48 (4), October 1958; Pp. 474-493. doi : 10.2307 / 211670
- ↑ a b c Brent S. Stewart, Harriet S. Huber: Mirounga angustirostris . In: Mammalian Species . tape 449 , 1993, pp. 1–10 , doi : 10.2307 / 3504174 ( full text (PDF file; 1.27 MB)). Full text ( Memento from March 18, 2014 in the Internet Archive )
- Jump up ↑ Ana M. Valenzuela-Toro, Carolina S. Gutstein, Mario E. Suárez, Rodrigo Otero & Nicholas D. Pyenson: Elephant seal (Mirounga sp.) From the Pleistocene of the Antofagasta Region, northern Chile. Journal of Vertebrate Paleontology 35 (3), April 2015; e918883. doi : 10.1080 / 02724634.2014.918883 .
- ↑ a b Jeff W Higdon, Olaf RP Bininda-Emonds, Robin MD Beck, Steven H. Ferguson: Phylogeny and divergence of the pinnipeds (Carnivora: Mammalia) assessed using a multigene dataset. BMC Evolutionary Biology 7, 2007. doi : 10.1186 / 1471-2148-7-216 .
- ↑ Olaf RP Bininda-Emonds, AP Russell: A morphological perspective on the phylogenetic relationships of the extant phocid seals (Mammalia: Carnivora: Phocidae) . In: Bonn Zoological Monographs 1996, Vol. 41.
literature
- JK Ling, MM Bryden: Mirounga leonina . In: Mammalian Species . tape 391 , 1992, pp. 1–8 ( full text (PDF; 1.1 MB)).
- Ronald M. Nowak: Walker's Mammals of the World . Johns Hopkins University Press, 1999, ISBN 0-8018-5789-9
- Judith E. King : Seals of the World . Cornell University Press, 1983, ISBN 0-8014-1568-3
Web links
- Mirounga leonina inthe IUCN Red List of Threatened Species 2011.2. Posted by: C. Campagna (IUCN SSC Pinniped Specialist Group), 2008. Retrieved April 13, 2012.
- Derek Block, Philip Meyer: Mirounga leonina in the Animal Diversity Net.
- Mirounga leonina in the Encyclopedia of Life