Otter
| Otter | ||||||||||||
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River otter ( lutra lutra ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Lutra lutra | ||||||||||||
| ( Linnaeus , 1758) |
The otter ( Lutra lutra ) is a marten that has adapted to aquatic life and is one of the best swimmers among land carnivores . It occurs in almost all of Europe and is about 130 centimeters long including the tail. A clearer name for this species is Eurasian otter , as it is in the group of otters are other species that otters are called, such as the Indian or American otters .
features
The otter has a head-trunk length of up to 90 centimeters, plus a 40-centimeter tail. The tail, which is rounded and muscular in cross section, serves the otter as a control and stabilization organ.
Otters have a shoulder height of around 25 to 30 centimeters. Adult otters can weigh up to 12 kilograms. On average, the females weigh around 7.4 and males 10.5 kilograms. The body is elongated and cylindrical and the legs are short, the head is rounded and blunt-snouted, and there are long whiskers on the muzzle, which are an important sense organ in murky water. The toes are webbed . The fur is light brown. With increasing age, the throat and front neck become whitish.
The fur of the otter has due to the unusual structure of his hair a particularly effective insulation against cold and wet: the hair, like a zipper , by microscopic another small, interlocking wedges and grooves interlocked . The result is an extremely dense fur braid, which holds insulating air bubbles in place, but at the same time repels water . In this way, the otter's skin remains dry and the body warm, even though, unlike dolphins , whales , polar bears or sea lions , it does not have a thick, insulating layer of fat . A total of 80 to 100 million hairs protect the otter from heat loss; that is from 60,000 to 80,000 hairs per square centimeter. The hair change in the otter takes place very slowly and the animal spends around ten percent of its waking time caring for its fur.
distribution
The otter can be found all over Europe . It is only missing in Iceland and the islands of the Mediterranean . In Asia it is common north to the Arctic Circle and a few kilometers beyond. However, he avoids the Central Asian steppes and deserts here. It is also found in Japan and as far as the Sunda Islands and in western North Africa ( Morocco and Algeria ). In the mountains it occurs at altitudes up to 2500 meters. However, within the range it is threatened in many regions. In Central Europe there are even larger populations in the Czech Republic , in eastern Germany and in the Bavarian Forest, as well as small populations in Austria. In France it was on the verge of extinction, but since it was placed under protection in 1973, the populations have been increasing again. It has been extinct in Switzerland since 1989 - individual animals have occasionally been found.
Up to 13 subspecies are described within this large distribution area. The exact taxonomic classification has still not been conclusively clarified. In Central Europe, which is nominate Lutra lutra lutra home, which in 1758 by Carl Linnaeus described.
habitat
Its preferred habitat are shallow rivers with overgrown banks and flood plains. The decline of such habitats and hunting have resulted in the otter disappearing in places and becoming extremely rare in many places. However, it can cope with all types of freshwater habitats, as long as the waters are clear, rich in fish and offer sufficient hiding places along the banks.
Otters are also found in salt water. You can find otters on the coasts of Germany (including the Vorpommersche Boddenlandschaft National Park ), in Scandinavia and Scotland.
He reveals his presence through well camouflaged exits on the bank. Otter droppings (solution), marking secretions and remains of prey can be found along the occasionally trodden otter paths. On muddy ground or in snow, you can not only see the footprints (footstep seals), but also the traces of the tail being dragged.
Way of life
There is no uniform way of life for otters: Depending on the environment (landscape, disturbances) and individual inclinations, otters adapt their way of life in order to be able to survive as well as possible. They are active at night and during the day. While resting on the bank, they move around in the water at the time of their activity. The animals are good swimmers and divers. They can stay underwater for up to eight minutes if not disturbed. When swimming, the head and neck protrude from the water, while the rest of the body remains under the water.
On the bank the otter digs a burrow, the entrance of which is about 50 centimeters below the surface of the water; the living chamber is located above the flood line and remains dry. An air shaft connects them with the outside world.
Food and subsistence
The otter eats what it can easily catch. Fish represent a large part of its prey spectrum, whereby it prey predominantly small fish species and among them slow and weakened animals. It therefore has a role to play in keeping fish stocks healthy. Other animals are also hunted by the otter: coots , ducks , gulls , muskrats , water voles , rabbits , snails , frogs , crayfish and insects , and occasionally it also takes carrion and eats mussels . Smaller prey animals are eaten in the water, larger ones brought ashore.
Reproduction
The otters do not mate in the water, but on land. The main mating season is in February and March. During this time, males join the females and always stay close to them.
The gestation period of the female is between 58 and 62 days. Then the one to four cubs who normally make up a litter are born. The young are blind when they are born, weigh around 80 to 100 grams and are rarely more than 15 centimeters long. The initially helpless animals crawl around the burrow for the first time when they are two weeks old, they open their eyes at the earliest on their 31st day of life. They make their first attempts to swim from the age of six weeks. They are suckled by the mother for between 8 and 14 weeks; however, they usually stay with the mother for fourteen months. During this time you will learn to hunt yourself.
Male otters become sexually mature at two years of age, females become sexually mature between 18 and 24 months and reproduce for the first time at an average of two and a half years.
Otters can make a whole range of different noises and calls while rearing their young, playing with young animals and fighting in territory. See also web links .
Enemies and life expectancy
Captured otters lived up to 22 years of age. Otters living in nature do not reach this age; only 15 percent of the young animals in a year are older than three years. On average, they live 8 to 13 years.
The enemies of the otter include the wolf , the lynx , the sea eagle and free-roaming dogs. However, it is mainly less experienced young animals that fall victim to them.
The otter's most dangerous enemy, however, is humans. Habitat destruction and water pollution, food shortages, road traffic and fish traps are the main reasons why otters do not reach old age.
Development history
The marten family, which also includes the otter, began to split into different lineages about 38 million years ago. The small and extremely agile hunters, to which the otter is one, developed from one of these lines. Fossils of the otter genus are found for the first time in the Middle Pleistocene , which means they are around a million years old. However, paleontologists are convinced that the findings so far do not represent direct ancestors of the otters.
Remains, which are clearly assigned to the Eurasian otter, are around 120,000 years old and come from the Eem warm period . Other fossil finds from Austria , among others, are significantly younger with an age between 18,000 and 10,000 years. They show that the otter was a typical element of the alpine fauna even in prehistoric times .
Inventory development
The otter had a bad reputation for a long time. He was believed to have killed lambs and was said to pull hunting dogs underwater and drown them there. In the Middle Ages , the hunt for the otter was considered useful and "enjoyable" hunting . In the 19th and early 20th century, the hunt intensified this marten, especially otter skins of furriers like to caps , collars and coats were processed. At the end of the 19th century, for example, the hunt for alleged fish robbers was even subsidized by the cantons and the federal government in Switzerland . The same was true for Germany .
Today the otter is under protection in most countries. In Germany the otter still falls under the hunting law , but hunting has been prohibited since 1968. The protection of the otter began at a point in time when the population of the animals had already been decimated for a long time. In most countries it was considered an endangered species at the time it was placed under protection. In Germany it became apparent that the otter populations were declining despite being protected. The construction of bodies of water , extensive drainage of habitats that are important for it and extensive clearing of riparian vegetation all contributed to this. At the same time, heavy metals , pesticides and polychlorinated biphenyls (PCB) made many otters no longer able to reproduce. With regard to the harmful influence of otters on fishing and pond management, which was claimed in the past and in some cases still today, studies have shown that the species prefers prey from natural waters even when it is easy to reach breeding ponds and only increasingly relies on fish from farmed ponds in areas with poorer living conditions .
The BfN lists the otter in Germany under risk level 1 as “critically endangered”. Thanks to good protective measures, the populations in Mecklenburg-Western Pomerania , Brandenburg and Saxony have been increasing again since around 1990. Due to anthropogenic influences, the species was almost extinct in Schleswig-Holstein at the end of the twentieth century. Since around 2000, however, a clear re-spread of the species has been noticeable here, which is evidenced, among other things, by faeces found on bodies of water and otters found dead on roads. Successful resettlements were also made in Bavaria , Bremen , Lower Saxony and Schleswig-Holstein. In Lower Saxony it occurs again in all suitable habitats. In northern Hesse and Baden-Württemberg there are residual stocks that are strictly protected. After Thuringia and North Rhine-Westphalia animals are already immigrated from neighboring regions again. Due to the negative influences to which the otter is exposed when repopulating a heavily anthropogenic transformed landscape, monitoring should not only consist of a control of the distribution or occurrence at the state level, but also the condition of the population (s) with regard to the protection of the species to verify. In addition, biological data from otters found dead and dissected allow insights into the population-biological processes within the species in Schleswig-Holstein. So far, only a few immigrant animals have been found in Berlin and Hamburg . Evidence of the otter has been available for several years. The otter is absent in Rhineland-Palatinate and Saarland .
In Austria it occurs mainly in the Waldviertel and Mühlviertel . There are also some populations in southern Burgenland and Eastern Styria . The population has been increasing again for about ten years. In 2017, Steven Weiss, University of Graz, researched the otters in Carinthia using fecal sample analysis; according to this, 360 individuals would live in the running waters of this state. In 2009–2017 the number would have increased by 19 percent annually. This favorable development enables the country to regionally allow the removal, i.e. the shooting, of a certain number of the protected animals. The decline in fish stocks in Lieser and Gurk by 90 and 80% is attributed to the otter. In contrast, nature conservation organizations emphasize that this cannot be blamed on the otter, but is primarily due to the poor ecological condition of the local rivers - caused by hydropower plants, regulation, pollution and global warming.
In Switzerland , for the time being, the last trace of an otter was found in 1989 on Lake Neuchâtel . Resettlement projects are still in the clarification phase. On the other hand, priority is given to maintaining the population in neighboring countries. Since 2004 there have been sporadic observations of individual animals of unknown origin in Zealand . In August 2005, during a flood, a pair of otters escaped from the Dählhölzli zoo in Bern. They settled on the Aare and successfully reproduced. An animal captured in November 2009 not far from Lake Murten turned out to be an Asian dwarf otter , which had escaped from a private owner. In the winter of 2009/10 an otter was detected in the Graubünden Alpine Rhine . He was repeatedly filmed by the video surveillance system on the fish ladder at the Reichenau power plant . The animal could not be seen, but there were tracks in the snow.
The stocks in France were estimated to be at least 2,000 specimens at the beginning of the 2000s, mainly in the regions of Brittany , along the Atlantic coast (e.g. on the Hourtin lagoon ) and in the Massif Central .
In the past centuries the otter also inhabited the coasts and regularly swam to the islands in the North and Baltic Seas . The otter population was able to survive in the Swedish archipelago and in Norway's fjords. It is now at home again in places on German coasts.
In the Czech Republic , the otter has been spreading again since the early 1990s and is now resettling around half of the country.
The IUCN classifies the otter overall as "low risk". However, the population trend is decreasing.
Reception in culture
heraldry
The otter rarely appears in heraldry as a heraldic animal, for example in the Brandenburg city of Schwarzheide and in the communities of Gossau and Männedorf , both in the canton of Zurich . The two municipalities of Ottersberg and Otterndorf in Lower Saxony and the municipality of Grambek in the Duchy of Lauenburg ( Schleswig-Holstein ) also have an otter in their coat of arms.
- See main article: Otter (heraldic animal)
additional
literature
- Otter Post . Journal of Aktion Fischotterschutz e. V., Hankensbüttel (appears quarterly with around 36 pages each. In 2004, the 25th year appeared).
- Claus Reuther: The Otter Center Hankensbüttel. In: Museums and excursion destinations in the Gifhorn-Wolfsburg area. Sparkasse Gifhorn-Wolfsburg, Gifhorn 1989.
- Claus Reuther, Antal Festetics (ed.): The otter in Europe. Results of the 1st International Otter Colloquium from October 28th to 31st, 1979 in Göttingen. Self-published, Oderhaus and Göttingen 1980.
- Kriegs, JO et al .: Current occurrence of the otter Lutra lutra (Linnaeus, 1758) in North Rhine-Westphalia and indications of its genetic origin . Nature and Homeland 70 (2010): 131-140. PDF
- Irene Weinberger, Hansjakob Baumgartner: The otter: a secret hunter returns. Haupt, Bern 2018, ISBN 978-3-2580-8084-0
Web links
- Lutra lutra in the endangered Red List species the IUCN 2008 Posted by: J. Ruiz-Olmo u. a., 2008. Retrieved February 24, 2009.
- Fish inventory survey in five selected bodies of water in Lower Austria. Vienna 2016.
- Otter Center Hankensbüttel and Aktion Fischotterschutz e. V.
- www.otterspotter.de - otter find data
- Pro Lutra Switzerland Foundation
- How otters stay warm and dry. On: Wissenschaft.de from August 20, 2005
- Otter photos
- tierstimmenarchiv.de : Access to the entry otter via "Database"> "Standard search" > Lutra lutra > "Search"
Individual evidence
- ↑ Kuhn, RA, Ansorge, H., Godynicki, S. et al. Acta Theriol (2010) 55: 211. DOI: 10.4098 / j.at.0001-7051.014.2009 (“ The hair density of adult Eurasian otters Lutra lutra (Linnaeus, 1758) and sea otters Enhydra lutris (Linnaeus, 1758) was analyzed using skin samples taken from frozen carcasses. Lutra lutra exhibited a mean hair density of about 70000 hairs / cm2 (whole body, appendages excepted), the mean individual density ranging from about 60,000 to 80,000 hairs / cm2. ")
- ↑ Jacquet, François: THE RETURN OF OTTER (LUTRA LUTRA) IN HAUTE-SAVOIE (FRANCE): DEVELOPMENT OF A NEW METHOD OF HABITAT ANALYSIS, in: Revue d'Ecologie, Vol. 64 (4): 2019, p. 359.
- ^ BfN: Lutra lutra (Linnaeus, 1758) .
- ↑ Otter killing by ordinance orf.at, February 3, 2018, accessed on February 3, 2018.
- ↑ WWF Austria: WWF criticizes plans to hunt otters in Carinthia. Retrieved April 14, 2019 .
- ↑ Federal Office for the Environment of April 3, 2005: An otter visiting Zealand. Retrieved November 11, 2009 .
- ↑ KORA Report No. 44f: Suivi des loutres de l'Aar. (PDF; 1.6 MB) Archived from the original on June 13, 2010 ; Retrieved November 11, 2009 .
- ↑ KORA-News of November 16, 2009: La loutre Fribourgeoise n'est sans doute pas une loutre d'Europe. Archived from the original on November 19, 2009 ; Retrieved November 16, 2009 .
- ↑ Berner Zeitung of November 17, 2009: The riddle about the otter has been solved. Archived from the original on November 20, 2009 ; Retrieved May 6, 2010 .
- ↑ Media release and pictures from the Office for Hunting and Fisheries Graubünden. (No longer available online.) Archived from the original on May 9, 2010 ; Retrieved May 6, 2010 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ So at least the current signs along the lagoon (last visited on January 11, 2020) and reports from residents about at least one copy that was unfortunately run over on Seestrasse.
- ^ Bendele, Robert: Répartition de la Loutre (lutra lutra L.) dans le département de l'ardèche - actualization. Center ornithologique Rhône-Alpes (CORA): 2001.
- ^ IUCN 2012. IUCN Red List of Threatened Species. Version 2012.1. < http://www.iucnredlist.org/ > Downloaded July 21, 2012.
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