walrus
| walrus | ||||||||||||
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Pacific walrus |
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| Systematics | ||||||||||||
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| Scientific name of the family | ||||||||||||
| Odobenidae | ||||||||||||
| Allen , 1880 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Odobenus | ||||||||||||
| Brisson , 1762 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Odobenus rosmarus | ||||||||||||
| ( Linnaeus , 1758) |
The walrus ( Odobenus rosmarus ) is a species of seal that occurs in the cold seas of the northern hemisphere . Two subspecies, the Atlantic ( O. r. Rosmarus ) and the somewhat larger Pacific walrus ( O. r. Divergens ), are distinguished. The walrus belongs to the order of predators and is the only species in the walrus family (Odobenidae).
The zoological name Odobenus is derived from the Greek ὀδούς odous , German 'tooth' , and βαίνω bainō , German ' to go' , and comes from the observation that walruses pull themselves on land with their tusks . It was awarded by Mathurin-Jacques Brisson in his work Le regnum animale in 1762 , while the original species name Phoca rosmarus goes back to the Swedish naturalist Carl von Linné , who still counted walruses among the real dog seals in his work Systema naturae .
The epithet of the Pacific subspecies divergens (diverging) comes from Latin and refers to the tusks.
features
Walrus bulls are about three and a half meters long, while the cows are three meters; the weight of a male can exceed 1200 kilograms, females weigh between 600 and 800 kilograms depending on the subspecies. Walruses can live up to 40 years.
The plump body of the walruses looks bald from a distance, but is covered by a stubby coat that is about one centimeter short and thins with age. The skin is extremely thick and wrinkled at about four centimeters; underneath is a five to eight centimeter thick layer of fat . It protects the animals from the cold and injuries caused by sharp ice edges or pointed stones. In adult males it is reinforced at the neck and shoulders and is used here to protect against injuries in rank fights among the males. At birth, walruses have a strong red-brown color, with age they become increasingly pale and finally are yellowish-brown. The color of a walrus can therefore be used to estimate its age. The chest and abdominal regions are usually darker than the back area; the fins are dark gray in the newborn, but take on a paler color over time.
denture
The most striking feature of the walrus are the upper canine teeth, which are formed into long tusks, which are also known as tusks . They are present in both sexes, but in the males they are usually longer, stockier, more angular in cross-section and also more straight, while the tusks of females are usually round in cross-section and have a stronger curvature. On average they are 50 centimeters long; exceptionally, record lengths of 1 meter are observed. The canines of young walruses are not yet developed, they do not break through until they are six to eight months old and are usually only visible after a year and a half because of the voluminous, wrinkled lip. The initially remaining tooth enamel wears out in the adult animals over time and is sooner or later completely lost. In older animals, the tusks are often very blunted from long use and sometimes even broken.
The most important function of the tusks, along with numerous other functions, such as defense against predators, as a headrest, to break breathing holes in the ice or as an aid when leaving the water, is to demonstrate the gender, age and social status of their wearer. By simply showing their imposing tusks, dominant animals of both sexes, for example, are regularly able to displace subordinate individuals from favorable resting places. As a result, a fight only occurs when two porters of approximately the same length meet.
While young animals initially still have full dentition, their lower incisors fall out as soon as the two tusks break through; behind the 3 to 4 Vormahlzähnen located molars are stunted anyway. The total number of teeth varies between 18 and 24 and can be expressed by the tooth formula 1–2 / 0 1/1 3–4 / 3–4 0/0.
Head and sense organs
The most characteristic feature of the roughly cuboid skull is the large protruding wart ( processus mastoideus ) of each temple bone ( os temporale ), to which the strong neck muscles attach. In contrast to the ear seals, walruses have no protrusions on the eye sockets ( orbita ) on their frontal bones ( os frontale ) and also have no crest . The rostrum , the snout, is blunt, the skin on the top is very keratinized.
Characteristic is the bristle whiskers made up of up to 450 whisker hairs, which hangs down like a trap from the upper lip and serves to recognize and differentiate between different types of prey. However, it is largely worn out in the wild and is only so prominent in animals kept in zoos.
The eyes of the walruses are very small compared to the size of the skull; Unlike the ear seals, they do not have externally visible ears. The middle ear bones are comparatively thin.
Fins
Like the probably related ear seals , walruses have very agile fins that allow them to reach almost any point on their body. They allow greater agility on land than, for example, the limbs of the seals , even if walruses are not as skillful as ear seals . The fins are usually triangular in shape, the upper fin side is slightly hairy, while the underside has no hair. The five toes each end in cartilaginous tips, on which the actual nails are located a little away from the toe ends.
Internal anatomy
Males have two air sacs in their throats that they can inflate to make different sounds. They probably have a second function as air cushions, with which the specific weight is reduced in the water, so that the animals can swim on the surface without great effort.
Arteriovenous anastomoses , cross-connections between arteries and veins that enable rapid heat exchange, are distributed over the entire surface of the body . Walruses resemble dog seals in this respect.
The penis bone is the cops having a length of about 60 centimeters, the longest in the animal kingdom, both in absolute length as well as in relation to the body size; the testicles are inside the body. The females have four mammary glands twice.
distribution and habitat
Most of the time walruses live on the Arctic drift ice . In winter they move south to avoid the pack ice, but usually do not leave the polar latitudes. There are four distinct populations:
- The Pacific walrus is found in the Bering Sea in winter ; in summer, the populations cross the Bering Strait towards the north and seek out the edge of the pack ice in the Chukchi Sea .
- The western populations of the Atlantic walrus live between Hudson Bay and the west coast of Greenland .
- The eastern populations of the Atlantic walrus live on the east coast of Greenland and in the area between Svalbard and the northwest coast of Siberia . The animals are less common further south; however, more than 20 records of walrus catches off the coast of the British Isles are known from historical times . More recently there have also been sightings of walruses, for example on the Shetland Islands ; Walruses have also been sighted off the Netherlands and on the French and Spanish coasts.
- Another population lives on the north coast of Siberia and is occasionally classified as a third subspecies (Laptev walrus, O. r. Laptevi ).
- A walrus population originally found in Iceland was exterminated by the Vikings .
The Atlantic walruses are characterized by shorter tusks and a slightly differently proportioned head with a wider occiput and a narrower facial skull.
The animals almost always stay in shallow coastal waters, close to the continental slopes or on pack ice. Although they usually do not go deeper than about 80 meters, diving depths of up to 180 meters have been proven in individual cases.
Way of life
nutrition
Walruses feed underwater and can dive for up to 30 minutes. They occasionally catch fish, but live mainly on shellfish , especially the genera Mya , Cardium and Clinocardium of snails , crustaceans such as shrimp or crab , squid , sea cucumbers , tunicates and worms as Vielborstern (Polychaeta) or Priapswürmern (Priapulida). When looking for organisms living in the sea floor, they have to dig it up. For this they mainly use their right fin (66%), the left much less often (4%). They also make use of their snouts (29%) and in some cases a self-generated jet of water that they direct onto the seabed (1%). The tusks are not used to search for food.
Clams and snails are cracked either between their forefins or by pressing their lips firmly together. From stomach contents it can be concluded that a walrus can ingest more than 50 kilograms of food.
Although small animals make up the main diet, the walrus also sometimes overwhelms very large prey. Other seals in particular are occasionally killed by a walrus, but attacks on seabirds have also been observed in rare cases; there is also fresh carrion . Seals are almost exclusively hunted by males who live solitary. In some cases cannibalism also occurred , with an old animal eating newborn walruses.
Locomotion
In the water, walruses use their muscular hind fins for propulsion, while the front fins are used as rudders. On land they often move forward with all four limbs. The weight rests on the "palms" of the front fins and the "heels" of the rear fins. Both “fingers” and toes face outwards; the former point to the rear, the latter to the front. Sometimes, however, only the front fins are used, while the rear fins are pulled along as with the dog seals.
Predators, parasites and pathogens
The walrus has hardly any enemies to fear. The polar bear occasionally tries to set off a herd in order to prey on solitary animals or young animals that remain behind, but will be careful not to attack an adult animal that can defend itself well with the help of its tusks. Occasionally, killer whale attacks on walruses are reported.
The skin of the walrus is a diverse habitat for numerous species of blood-sucking lice (anoplura); Scratchworms (Acanthocephala) and roundworms (Nematoda) are the most common internal parasites .
Broken tusks and bacterial infections of the fins or eyes quickly lead to weight loss and death; The genus Brucella in particular is frequently identified . The effects of viral infections caused by caliciviruses and morbilliviruses are still largely unexplored.
Social behavior
Walruses spend half of their lives on the coasts of Arctic islands or on the edge of the pack ice, where they gather in large herds. Outside of the mating season, these herds are usually separated according to sex; Exceptions to this rule exist in some northern Canadian populations, where males and females stay together year round.
For communication within the groups, walruses have a large repertoire at their disposal, which includes grunting, roaring and screeching sounds. Often the animals lie close to each other or even on top of each other and rub their bodies against each other or scratch each other, a behavior that is presumably used to remove parasites . There is a fixed hierarchy based on the size of the tusks and height. Above all between the bulls there are fights outside of the mating season, the reason for which may be a preferred resting place on land. If threatening gestures are unsuccessful, fights arise in which the tusks are used and which can end with bloody wounds.
The social structure of the herds at mating season and the reproductive system itself differ somewhat between the subspecies. Walruses of the Pacific subspecies gather in medium-sized groups consisting of numerous females and their offspring and a few accompanying bulls. Where the hunt by humans has not yet had any serious consequences, these can temporarily or permanently unite to form even larger herds, which then comprise several thousand animals. Coastlines of 100 kilometers and more are then taken over by the colonies. The males spend most of the time in the water and are in strong competition with one another. Unlike the Atlantic subspecies, however, they are unable to defend individual females or lead a harem. As a result, elaborate rituals of partner recruitment have developed: the males generate sequences of clicks and bell-like sounds under water, which they produce by inflating their air sacs, on the other hand various whistling tones on the surface; in particular, the bell sounds are only performed during the mating season. Today it is assumed that this rich palette of sounds and their incessant performance correspond to the function of birdsong, that is, to attract the attention of competitors and possible partners. An important basis of this system is the choice of mate that the females choose. Bulls that have not yet reached sexual maturity usually gather in separate single-sex groups outside the mating areas.
The more stable conditions in the Atlantic and the generally smaller groups have probably led to the subspecies there having a harem system instead. Even if similar vocalizations can be registered, they probably only play a subordinate role in the choice of mate: In contrast to the Pacific walruses, the males here are able to monopolize larger groups of females due to the development of stable hierarchies. In some colonies there is one strong bull for every twenty cows, while younger and weaker males have no chance in competition and are pushed to the edge of the colony. On the other hand, fierce fighting can occur between bulls of about the same strength.
Reproduction
Mating will likely take place in the water between January and February. After fertilization, the egg remains dormant for four to five months ( egg rest , i.e. it does not develop any further) before the actual eleven month gestation period begins. As a rule, the birth takes place in May of the year after next, so that there is a two-year reproductive rhythm that can be increasingly lengthened in older cows. Each pregnant cow gives birth to only one calf; Twin births are extremely rare. The low number of births and offspring means that walruses have an extremely low reproduction rate, even for mammals, and can therefore only compensate for population declines over long periods of time.
At birth, the calves are less than a meter long, weigh around 50 kilograms and can swim immediately. For the first six months they are only nourished by breast milk, after which the food is increasingly supplemented by other components. The young are weaned after two years, but remain with the mother for another one to three years. Females become sexually mature at four to ten, but on average around six years, while males reach physiological sexual maturity at nine to ten years. However, they are only able to compete against conspecifics when they are around fifteen and actually gain access to females, a condition that is known as social sexual maturity .
Tribal history
The walrus family has been fossilized since the Miocene and, like the ear seals, probably comes from the northern Pacific. In the Miocene and the subsequent Pliocene there were several species of walrus that looked very much like today's sea lions . In the late Miocene, about five to ten million years ago, they were apparently the dominant and at the same time most diverse seal group in the Pacific. At this time, there was also a switch from mostly fish-based food to a range of prey dominated by the fauna of the seabed ( benthos ) in some species , which was also accompanied by morphological changes. This included, for example, changing the propulsion in the water to the hind fins and enlarging the canine teeth.
There are two hypotheses about the colonization of the Atlantic, which took place around five to eight million years ago. According to one, it took place along the North American or Siberian coasts of the Arctic Ocean, according to the second, the ancestors of today's walrus immigrated to the Caribbean before the land bridge between North and South America was formed and from there they reached the polar waters of the Atlantic.
Whether the Pacific populations became extinct in the meantime and the Pacific was only secondarily repopulated in the Pleistocene about a million years ago by Atlantic populations immigrating along the coasts of the Arctic Ocean, or whether the ancestors of the Pacific subspecies can be traced back to the original inhabitants of the Pacific remains to be seen still unclear.
What is certain is that the walrus colonies in the Pleistocene lived much further south than they are today and were even found on the coasts of Central Europe and California because of the favorable ice age conditions.
Human and walrus
Indigenous peoples
The walrus has always played an important role in the life and culture of Arctic peoples, especially the Inuit , Chukchi and Koryaks . They used virtually all parts of the body: The walrus provided food (meat, entrails and offal), fuel (eg. Tran ), building materials (walrus, stomach skin, bones and tusks) for Erdsodenhäuser and boats ( Aleutian Kayak , kayaking and Umiak ) and Material for clothing (walrus skin, stomach skin). Walrus meat and even fins, fermented in the earth for months, are still considered a delicacy today. The walrus also plays an important role in the mythology and folklore of the indigenous peoples.
Some ethnic groups, especially the coastal Chukchi and the Yupik on the Bering Sea , still cover up to half of their protein requirements with walrus meat , and the rest with the meat of bearded seals , ringed seals and whales . Walrus ivory carvings have a long artistic tradition in the Arctic . To this day, the creation of works of art made of walrus ivory contributes to value creation in many places in the Arctic, for example in many villages in Chukotka (especially Uelen ) and Alaska (e.g. Shishmaref ) and Nunavut (including Iglulik ), although international trade in walrus ivory is restricted by the Washington Convention on Endangered Species .
In Alaska and Russia there is a regulated subsistence hunt of four to seven thousand Pacific walruses annually, including a high proportion (about 42%) of injured animals. In Greenland and Canada, where the numerically smaller Atlantic populations are still threatened, only a few hundred are shot a year. It is difficult to determine the threat to the populations from such hunting, since there is still considerable uncertainty with regard to the population estimate and population parameters such as fertility and mortality .
Walrus hunting by non-indigenous people
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With the advance of white hunters into the Arctic seas, a fatal situation developed for the walrus colonies. Walruses were now hunted intensively, mainly because of the ivory of their tusks, which is only inferior to that of elephants in terms of quality. Walruses were found along the east coast of North America as far as Cape Cod and the Gulf of St. Lawrence . Several thousand walruses were shot there every year in the 16th and 17th centuries. In the 19th century, all walruses south of Labrador were wiped out. In search of colonies that were not yet extinct, the hunters penetrated into ever more remote regions. The extent to which walruses were slaughtered is shown by the estimate that between 1925 and 1931 around 175,000 walruses were killed on the coasts of the Canadian Baffin Island alone . The Atlantic walrus was almost extinct for a time. Today the population of Atlantic walruses is estimated at around 15,000 animals; for unknown reasons, a recovery has not yet occurred by far, despite protective measures.
The Pacific walrus was decimated in a comparable way, although hunting only began much later. Due to protective measures by the USA and Russia, however, the population has recovered, so that the number of Pacific walruses is again around 200,000 today and the species is no longer considered to be threatened.
pollution
With regard to the pollution of their habitat, walruses are primarily affected by oil gaps, as high-molecular hydrocarbons can accumulate on the seabed and thus in the walruses' foraging and reduce the number of their prey. Due to the low fat content of their food, the exposure to organic chlorine compounds and heavy metals such as mercury is lower than that of other marine mammals (seal-hunting walruses are an exception, as they absorb pollutants from this food source). Regular noise, such as that associated with airfields near human settlements, can lead to nearby mating sites being abandoned.
How global warming will affect is still uncertain. On the one hand it is known that walruses once lived in much warmer sea areas; on the other hand, studies of Pacific populations show that a decline in the reproductive rate is closely related to the loss of large contiguous areas of pack ice. In addition, the effects of rising sea temperatures on walruses' prey are unpredictable.
Conduct towards humans
If humans stay out of the walrus' flight distance , they will observe them curiously but are usually not very concerned. However, if the person comes too close to it (e.g. in a boat), the walrus usually withdraws from its bed on the ice floe into the protective water and submerges for a short time. In individual cases, however, people can also be attacked. In particular, smaller boats such as kayaks are occasionally knocked over by aggressive cops and the occupants are attacked (often with fatal consequences). The ethnologist and anthropologist Barry Lopez even tells of a bull walrus who attacked a person on an ice floe. A walrus cow wrecked a Russian Navy landing craft, presumably to protect her young.
Zoos
Occasionally walruses are kept in zoos. The walrus Antje , for example, gained popularity as the mascot of the North German Radio . In Germany, no walrus was kept in captivity for 5 years after Tanja , a 33-year-old female walrus, was euthanized in the Hanover Zoo in 2007 because of old age problems. In July 2012, the new Arctic Ocean opened in the Hagenbeck zoo , where the walrus Neseyka currently lives with three other female walrus and a bull walrus named Odin. A breeding group is to be set up in the future. In June 2014 a walrus bull (Thor) was born in the Hagenbeck Zoo, making it the first walrus calf in Germany to be born in captivity. On June 5, 2015, also in Hagenbeck, Loki, a female walrus calf with a deformity was born, it died on August 21, 2017. Nevertheless, species conservation is supported by breeding: on June 17, 2018, a small walrus bull was born there World. The mother of the young is the female walrus Dyna.
The walrus in lyrics
The Walrus and the Carpenter (Engl. The Walrus and the Carpenter ) is a poem that the girl Alice in Lewis Carroll's book Through the Looking Glass is performed by Tweedledum and Tweedledee. It comprises 18 stanzas and contains surreal nonsense elements, which are discussed in conversation between the walrus and the carpenter during the walk on the beach. Only a few oysters follow them by invitation, then more and more oysters . The poem ends with the protagonists casual consumption of these shellfish, which causes a conflict in Alice as to which of the two she likes less. There is no answer to this question.
Also inspired by this poem I Am the Walrus of the Beatles from 1967 used absurd and psychedelic word constructs and metaphors.
nomenclature
- C. v. Linné: Systema naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus differentiis, synonymis, locis. Curt, Magdeburg 38,1758,1 (10th edition), Georg Emanuel Beer, Leipzig 1788 (13th edition), Trustees British Museum, London 1956 (reprint. Faks.).
- MJ Brisson: Le regnum animale in classes IX distributum, sive synopsis methodica sistens generalem animalium distributionem in classes IX, & duarum primarum classium, quadrupedum scilicet & cetaceorum, particularem dibvisionem in ordines, sectiones, genera & species. T. Haak, Paris 1762.
literature
- Ronald M. Nowak: Walker's Mammals of the World. Johns Hopkins University Press, Baltimore 6 1999, ISBN 0-8018-5789-9
- Barry Lopez: Arctic Dreams. Btb bei Goldmann, Munich 2000, ISBN 3-442-72642-5
Web links
- Walrus Projects at the Alaska Science Center (English)
- Odobenus rosmarus in the endangered Red List species the IUCN 2006. Posted by: Seal Specialist Group, 1996. Retrieved on 12 May, 2006.
Individual evidence
- ^ Arctic walrus spotted in North Ronaldsay and Sanday. BBC News, March 9, 2018, accessed March 9, 2018 .
- ↑ Xénia Keighley, Snæbjörn Pálsson, Bjarni F Einarsson, Aevar Petersen, Meritxell Fernández-Coll, Peter Jordan, Morten Tange Olsen, Hilmar J Malmquist: Disappearance of Icelandic walruses coincided with Norse settlement. Molecular Biology and Evolution, msz196, doi: 10.1093 / molbev / msz196
- ↑ Handbook of the North Pacific (PDF file; 1.29 MB)
- ↑ J. Forsyth (1992) A History of the Peoples of Siberia: Russia's North Asian Colony, 1581-1990 . Cambridge University Press, London
- ↑ W. Bogoras. (1902) The Folklore of Northeastern Asia, as Compared with That of Northwestern America. American Anthropologist, New Series , Vol. 4, No. 4. (Oct.-Dec., 1902), pp. 577-683.
- ↑ AI Kozlov, and Zdor, EI (2003) Whaling Wall as on element of Indigenous Diet in Chukotka. "The Anthropology of East Europe Review: Central Europe, Eastern Europe and Eurasia. Special Issue: Food and Foodways in Post-Socialist Eurasia", 21 (1): 127-137.
- ^ Eleanor, EW, MMR Freeman, and JC Makus. 1996. Use and preference for Traditional Foods among Belcher Island Inuit. Artic 49 (3): 256-264.
- ↑ Chester S. Chard (1955) Eskimo Archeology in Siberia. Southwestern Journal of Anthropology , Vol. 11, No. 2.
- ↑ C. Taksamiin (1990) Ethnic Groups of the Soviet North: A General Historical and Ethnographical Description. in Arctic Languages, to Awakening ( PDF )
- ^ Ivory ( Memento from March 15, 2008 in the Internet Archive )
- ↑ Garlich-Miller, JG and DM Burn (1997) Estimating the harvest of Pacific walrus, Odobenus rosmarus divergens , in Alaska. Fish. Bull. 97 (4): 1043-1046.
- ^ Witting, L. and Born, EW (2005) An assessment of Greenland walrus populations. ICES Journal of Marine Science. 62 (2): 266-284.
- ↑ Garlich-Miller et al. (1997)
- ↑ Barry Lopez: Arctic Dreams, dtv (1st edition, p. 149) Munich 1989. ISBN 3-423-11154-2
- ^ Rory Sullivan, Darya Tarasova: Walrus sinks Russian Navy boat in the Arctic Ocean. In: CNN. Retrieved September 27, 2019 .
- ↑ Press service of the Russian Navy (Northern Fleet): Report of the Russian Navy on the destruction of a boat by a walrus cow. Russian Navy Press Service (Northern Fleet), September 18, 2019, accessed on September 27, 2019 (Russian).
- ↑ Hagenbeck: Eismeer for polar bears , walrus and Co. In: NDR.de. July 5, 2012, archived from the original on July 6, 2012 ; Retrieved July 9, 2012 .
- ↑ Second walrus birth. Walrus offspring at Hagenbeck ( Memento from June 10, 2015 in the Internet Archive ), hamburg.de, accessed on June 10, 2015.
- ↑ Walrus baby born , hagenbeck.de, accessed on June 26, 2018.
- ^ Lewis Carroll The Walrus and the Carpenter at Poetry Foundation
