narwhal
| narwhal | ||||||||||||
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Narwhals |
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| Monodon | ||||||||||||
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| Monodon monoceros | ||||||||||||
| Linnaeus , 1758 |
The narwhal ( Monodon monoceros ) is a type of toothed whale (Odontoceti). Together with the closely related white whale ( Delphinapterus leucas ) it forms the family of the gudgeon whales (Monodontidae).
Features and properties
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Without a tusk, the narwhal measures four to five meters. The male weighs around one and a half tons, the female a little less than a ton. The narwhal lacks a fin . However, it has a series of irregular bumps along its back. The pectoral fins, known as flippers , are relatively short, rounded at the end of an ovoid and curved upwards. The fluke is strongly convex at the rear edge of both wings and thus differs significantly from that of all other whales. The head is relatively compact. A pronounced snout is missing and the mouth is very small and narrow with the corners of the mouth bent upwards.
The basic color of the narwhal is a very light brown to white. The head and neck as well as the back are dark, almost black, as are the edges of the flippers and the fluke. The sides are speckled with gray and blackish brown spots. Older animals are usually lighter in color than younger ones.
The most prominent feature of the males is their tusk (see also Ainkhürn ). It is a (usually the left) canine tooth (caninus) of the upper jaw , which breaks through the upper lip in a counter-clockwise direction and can be up to three meters long and weigh eight to ten kilograms. Probably the largest example in the world is 2.74 meters long in the German Leather Museum in Offenbach am Main .
The only other tooth is also in the upper jaw and usually does not break out. In the male, additional teeth are created in the embryonic jaw, but usually do not develop any further. Where this happens in rare cases, two tusks can also develop. In the female, the teeth are usually developed normally, but occasionally one or even two tusks also develop as in the male (which makes it difficult to differentiate between the sexes). It is not uncommon for the tusk to break off. Then the fracture site closes with new dentine .
For a long time, the significance of the tusk gave rise to somewhat unusual speculations. Views of how the tooth is used to break through the ice sheet or to spear fish, to rummage through the seabed or as an instrument for echolocation have been controversial. Two possible functions have recently been favored: the hierarchy-determining characteristic of dominance (see section on reproduction) or the sensory organ. The latest studies have shown that the tooth contains around 10 million nerve endings, with the help of which, in addition to water temperature and pressure , the salt content of the seawater and the quantity of prey can be determined depending on the depth.
Narwhals are mammals and therefore warm-blooded animals . They are insulated from the cold by a layer of fat under the skin, the bubbling , up to ten centimeters thick . The most important physical adaptations took place in sensory perception in an environment predominantly determined by acoustic stimuli and in the storage of oxygen . The narwhals (like their close relatives, the beluga or belugas) communicate acoustically through their “songs”, and how the sound waves they emit are perceived by us humans. The narwhal stores the oxygen in a way that enables it to draw from its supply for around fifteen minutes while diving: around 10% remain in the lungs, around 40% each go into the blood and muscle tissue, the remaining 10% in other types of tissue. In the blood, as in humans, the oxygen is bound by hemoglobin , in the muscle tissue by myoglobin , which, as in all marine mammals, stains the muscle flesh dark. The blood absorbs little nitrogen, so that when surfacing does not develop the typical diving disease for humans . The breathing air is then expelled from the lungs like an explosion - the whale "blows".
distribution
Narwhals are common throughout the Arctic Ocean and always stay close to the pack ice . The whales are most common around Greenland , Baffin Bay , Hudson Bay and along the coast of Siberia . They are less common on the coast of Alaska , in the Chukchi Sea and the East Siberian Sea . Today it is assumed that the animals east and west of Greenland are two relatively strongly separated populations .
In summer, narwhals migrate further north than any other mammal. You will then stay in the fjords of Greenland , especially in the Inglefield Fjord , in the Canadian Arctic and around Svalbard . Even in winter, narwhals usually stay north of the Arctic Circle .
Apart from Svalbard, narwhals only occur as random visitors in Europe. As can be seen from documentation, only about 20 narwhals have been sighted here in the last 200 years, mainly off the coast of Iceland and Scandinavia , where they occasionally stranded. Stray narwhals were very rarely seen even in the North Sea. The southernmost sighting comes from the Zuiderzee in the Netherlands (1970).
Way of life
Narwhals feed on some types of fish , octopus and crustaceans , which they literally "suck into their mouths" through the suction created by their powerful lips and tongue. The simultaneous occurrence of narwhals and white whales in the same region is very rare and is naturally avoided by different summer and winter reasons. In cases where such overlaps nevertheless occurred, it was possible to observe how the animals circumvented competition by looking for food at different water depths. The narwhals preferred the deeper water layers.
In addition to humans, the killer whales ( Orcinus orca ) are probably the greatest enemy of the narwhals. They drive the narwhales towards the coast when they hunt and can thus capture them more easily. When killer whales approach, but also ships or the sound of ice breaking, the narwhals show a behavior known as adlingayuk ( Inuktitut ): They become motionless and sink silently into the water.
For Northwest Greenland were the main source of food than in spring and summer Arctic cod ( Boreogadus saida ) and the Greenland cod ( Arctogadus glacialis ) determined. Fish were also found to be the main food for this time of year in other analyzes (about 93 percent of the stomach content on average). In the late summer and autumn, on the other hand, the proportion of cuttlefish and crustaceans predominates. A narwhal eats around 45 to 80 kilograms per day, depending on the season. Depending on the source, it dives up to 350 or even up to 500 meters deep in search of prey and remains under water for about fifteen minutes. To find the food he uses his " sonar system ", for which he emits intensive "clicks". Other sounds such as whistling, gasping and clicking series - especially in the ultrasonic range - are used for communication .
Narwhals stay near the pack ice all year round; within the ice surface they can be found in polynyas and at breathing holes. Holes in an ice sheet over 15 centimeters thick are opened or kept open by powerful blows with the forehead. Although herds of a thousand animals can come together during the seasonal migrations, family groups (“narwhal schools”) usually only consist of five to twenty animals - one adult male as well as several females and young animals. As long as they are not old enough to take over the management of a school, young males form associations.
Occasionally the polar bear ( Ursus maritimus ) is said to prey on narwhals. The Greenland Shark ( Somniosus microcephalus ) is unlikely to attack narwhals and only eats the carcasses of dead whales in nets. On the other hand, fatal attacks by walruses ( Odobenus rosmarus ) are documented. Rapidly freezing ice can trap narwhals in bays or fjords, a phenomenon known as sassat in Greenland . The whales can then no longer escape and are forced to keep ice holes open to breathe; eventually they die of exhaustion or are captured by Eskimo hunters.
Reproduction and development
Narwhals become sexually mature between five and eight years of age ; however, the first pregnancies do not occur until the age of seven to twelve. The male narwhals then have an average length of about 3.90 meters, the females about 3.40 meters. The females are evidently fertile several times a year; however, the mating season is only between late March and early May.
Little is known about the reproductive behavior of the narwhals themselves. It has occasionally been observed that rival fights regularly take place between the males in which the tusks are used as weapons. Broken teeth and forehead scars are not infrequently a result of these disputes; even male skulls with broken tooth tips from opposing males were found. According to Lopez (1987), the males place their tusks side by side in opposition, and the animal with the shorter tusk receives abrasions or sometimes serious stab wounds in such fights - an indication of the hierarchical importance of the tusks.
The animals are obviously polygynous, so they mate with several females, which they defend against rivals. The mating behavior itself has not yet been observed. In one case, DNA tests showed that a conspicuous whale skull belonged to an animal that had emerged from a mating of a female narwhal with a male beluga .
The wearing time lasts about 14 to 15 months; the births take place accordingly in the summer between May and August. The usually only boy is around 150 centimeters long and weighs around 80 kilograms at birth, twin births are rare. The tusk breaks through during the first year of life and only develops to full length over the course of several years. Suckling is likely to last for two years. During this time, the mother will not become pregnant again.
The lifespan of narwhals is around forty years.
etymology
The first scientific description of the narwhal comes from Carl von Linné (1758) under the name Monodon monoceros , which is still valid today . The German name narwhal is probably derived from the Norwegian word nar , which can be translated as "corpse" and should refer to the appearance of the skin, which is reminiscent of a human corpse. Another interpretation is based on the old German narwa "narrow" and refers to the tusk.
Systematics
The narwhal is the only species of the genus Monodon and, together with the white whale ( Delphinapterus leucas ), forms the family of the gudgeon whales (Monodontidae). This is justified primarily with various skull features , the fused cervical vertebrae as well as with enzymatic and immunological features.
Humans and narwhals
Economical meaning
The Inuit of Greenland and Canada still traditionally hunt the narwhal for food and because of the tusk (see below). The offal and muscle meat play an important role as food for humans and dogs . The whale skin or whale rind (Inuktitut “maktaaq”, Greenlandic “mattak”) is considered a delicacy , like the white whale . The oil of oil obtained by the Inuit from beaten whale blubber used to be used as a source of light and heat and is still of traditional significance today when it is used to ignite a stone oil lamp ("Qulliq"). The domestic trade in "mattak" is still an important source of income for the Inuit in Greenland . In the Thule area, for example, around 150 to 200 narwhals are shot annually using traditional methods. Overall, the catch quota of narwhals in Greenland and Canada is around 1,000 to 1,100 animals annually. With an assumed total population of 23,000 narwhals, such catch numbers are, according to various experts, just about tolerable for population growth.
An important aspect for economically operated narwhal fishing was the extraction of the tusks. First reports of narwhal's teeth trade appear around 1100; the Vikings exchanged them for Inuit on their Greenland voyages. The ivory teeth of narwhal, walrus and elephant and objects made from them are still considered to be very valuable; however, the hunt for the animals mentioned and the ivory trade are strictly regulated.
Cultural meaning
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Since the Middle Ages, the narwhal tooth has been regarded as the forehead weapon of the unicorn described in fables , whose existence seemed to be secured by this only tangible evidence. As long as the origin of the turned racks was unknown, this " Ainkhürn " was weighed in gold . The narwhal tooth has been a relic in the possession of sacral institutions in Europe since the 13th century . The Church Fathers and after them numerous medieval authors confirmed that the unicorn hunt was equated with the Incarnation of Christ through the Virgin Mary . The legend of pagan origin was thus legitimized to be present in medieval writings and images. Crusaders stole two narwhal tusks in Constantinople and donated them to St. Mark's Basilica in Venice , where they are still kept today.
The belief in the effect of the "horn" as an antidote , adopted by ancient authors from Asian sources of the legend , was always present in Islam and was given even greater weight in Europe through the affection of Christological symbolism . In the 14th century, secular rulers began to include narwhal teeth in the state treasury. The Habsburgs owned a narwhal tooth and several objects made from its ivory . In 1671, the Danish King Christian V was crowned on a throne made entirely of narwhal's teeth.
Healers spread the doctrine that potential victims of poison attacks are immune to the use of cups or dishes made from the rod of the unicorn. In addition, doctors used narwhal tooth powder as a cure for the plague . The equivalent that was put on the scales ended up being twenty times the weight of a tooth in gold.
It was not until the 17th century that Nordic whalers were able to get the coveted tooth themselves. Scientists and wealthy private individuals could also afford narwhal teeth and studied the existence of the mythical animal and the pharmaceutical effectiveness of this forehead weapon. In 1638 the doctor and natural scientist Ole Worm recognized the supposed unicorn rod as a narwhal tooth and put an end to the misunderstanding without questioning its effectiveness as a medicine. Worm's findings did not detract from the belief in the existence of the land unicorn. Most scientists readily accepted the narwhal tooth as the rod of a sea unicorn. Only the symbolic value of the rotated tooth, which was tied to the land animal, was lost. Due to the increased supply, prices collapsed completely around the middle of the century, especially as the plague wave ebbed after the Thirty Years War .
Today, the ivory of the narwhal tooth, along with that of walrus teeth, is an important starting product for valuable sculptures by Inuit artists .
Ecological damage
As for all marine mammals, pollution poses a great threat to the narwhals. As fish eaters, they take up the toxins deposited in their prey, especially heavy metals such as mercury , lead and cadmium , and store them in the liver , kidneys , muscle tissue and in the Body fat. Heavy metal loads vary from region to region. While cadmium pollution is extremely high in Canadian waters, lead levels are significantly excessive around Greenland.
Among the chlorinated hydrocarbons derived from pesticides , the polychlorinated biphenyls (PCB) play a role, along with dichlorodiphenyltrichloroethane (DDT), dieldrin , hexachlorocyclohexane (lindane) and chlorobenzene . These substances are mainly found in the adipose tissue of whales. Comparisons with exposure to other whales have shown that narwhals appear to break down organic toxins more slowly than other toothed whales.
Protection provisions
The narwhal is internationally protected. It is listed in Appendix II of the Washington Convention on Endangered Species ; international trade in narwhal products is accordingly prohibited. In addition, there are special laws in various states that strictly regulate the hunting and trade in narwhal products.
Special rules apply to the Inuit of Canada and Greenland to preserve traditions. The narwhal in Canada has been protected by the “Fisheries Act” since 1971, but a quota of five animals per year and hunter is allowed for the indigenous population. The law has been tightened since 1978: Today, young animals and females with young animals are fully protected in Canada. In addition, carcasses of killed narwhals must be completely recycled. The quota is controlled by a label system. Hunters are required to put a label on every tusk and carcass. Possession of a tusk or a carcass without a label is a criminal offense.
Only residents of Greenland who are designated hunters are allowed to hunt narwhals in Greenland. There is no quota regulation, but the fishing methods are regionally regulated in order to keep fishing losses low. In addition, no more whales may be killed than can be transported to the hunter's hometown immediately after the hunt. All of the meat must be used. It is forbidden to catch whales with motor boats in the area around Thule .
In Norway, small whales such as the narwhal can only be caught with special permission from the Ministry of Fisheries, which is why the narwhal is practically not hunted in Norway. In the successor states of the Soviet Union , the narwhal is fully protected. The "Marine Mammal Protection Act" of 1972 prohibits the importation of narwhal products into the USA. In Europe, the import into all EU countries was restricted by the EU Directive No. 3626/82 from 1982 with validity until December 31, 1996 prohibited and the import ban maintained by EU regulation 338/97 of December 9, 1996.
literature
- Mark Carwardine: Whales and Dolphins. Delius Klasing, Bielefeld 1996, 2003, ISBN 3-7688-1456-4 .
- Pia Comtesse-Weidner: Investigations on the head of the fetal narwhal Monodon monoceros. An atlas on the development and functional morphology of the sonar apparatus . VVB Laufersweiler, Gießen 2007, ISBN 978-3-8359-5114-3 (plus dissertation, University of Gießen 2007; full text ).
- Vic Cox: whales and dolphins. Karl Müller Verlag, Erlangen 1994, ISBN 3-86070-194-0 .
- Wolfgang violence: whales and dolphins - top performers of the seas. Springer Verlag, Berlin-Heidelberg 1993, ISBN 3-540-56668-6 .
- Ralf Kiefner: whales and dolphins worldwide. Book of diving , internat. Underwater magazine. Year Top Special Verlag , Hamburg 2002, ISBN 3-86132-620-5 .
- J. Niethammer, F Krapp (Ed.): Handbook of Mammals in Europe. Vol. 6. Marine mammals. T. 1A. Whales and Dolphins - Cetacea. AULA, Wiesbaden 1994, ISBN 3-89104-559-X .
- Barry Holstun Lopez : Arctic Dreams. Claasen, Düsseldorf 1987, Goldmann, Munich 2000, ISBN 3-442-72642-5 .
- RR Reeves, BS Stewart, PJ Clapham, JA Powell: Sea Mammals of the World. A Complete Guide to Whales, Dolphins, Seals, Sea Lions and Sea Cows. Black, London 2002, ISBN 0-7136-6334-0 (guide with numerous pictures).
- Gérard Soury: The great book of the dolphins. Delius Klasing, Bielefeld 1997, 2000, ISBN 3-7688-1063-1 .
- Heathcote Williams: continent of whales. Zweiausendeins, Frankfurt 1988, 1998 (20th & 21st ed.), ISBN 3-86150-058-2 .
- M. Würtz, N. Repetto: Underwater world. Dolphins and Whales. White Star Guides. White Star, Vercelli 2003, ISBN 88-8095-943-3 .
Web links
- Monodon monoceros in the endangered Red List species the IUCN 2008. Posted by: TA Jefferson and others, 2008. Accessed on December 31 of 2008.
- Klaus Minges: Church treasure and cutlery: The unicorn. (PDF; 65 kB)
- Mechthild Müser: The narwhal - unicorn of the arctic ocean Bavaria 2 radio knowledge . Broadcast on December 6, 2019 (podcast)
Individual evidence
- ↑ Guinness Book of Records 1992, Ullstein, ISBN 3-550-07750-5 .
- ↑ Riddle about the "horn" of the narwhal solved (on scinexx.de)
- ↑ Mikkel Skovrind et al .: Hybridization between two high Arctic cetaceans confirmed by genomic analysis , Scientific Reports, Volume 9, 2019, Article No. 7729. doi: 10.1038 / s41598-019-44038-0 .