Pilot whale
| Pilot whale | ||||||||||||
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Common pilot whales ( Globicephala melas ) |
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| Scientific name | ||||||||||||
| Globicephala melas | ||||||||||||
| ( Traill , 1809) |
The pilot whale ( Globicephala melas ), from Faroese grind ,> grindahvalur , also known as pilot whale or falsely Calderon dolphin , is a species of dolphins ( Delphinidae ). To distinguish it from the short-finned pilot whale , it is sometimes referred to as the common pilot whale or long-finned pilot whale .
features
The male animal reaches a length of three to six, a maximum of eight meters and a weight of a maximum of three tons. Females are slightly smaller with a maximum length of 6 meters. The body is almost cylindrical, the spherical head is hardly separated from the body and the melon towers over the very short snout of the animals. The fin is elongated and narrow in adult animals. This also applies to the flippers , which can take up almost a fifth of the body length. The fluke is very heavily indented in the middle.
The color is black with the exception of a whitish area below the chin, which runs along the stomach as a narrow line to the anus . This drawing is reminiscent of an anchor with the tip pointing towards the chin of the animal. In some individuals, there is also a lighter area behind the eye and another behind the dorsal fin.
distribution
The mammals prefer temperate and cold waters; in the southern hemisphere they inhabit all oceans, in the northern hemisphere only the Atlantic . The thirtieth degree of latitude north and south forms the approximate limit of the separate distribution areas. There were once pilot whales in the North Pacific, but for unknown reasons they died out around the 10th century without human intervention.
The whale can be found almost everywhere in European waters, especially around Iceland , in the Barents Sea , off the coast of Norway and north of Great Britain . In the Mediterranean you can often find it in the area of the Strait of Gibraltar and Corsica . The animals are less common in the Tyrrhenian Sea and the Adriatic Sea and the North Sea . In the southern part of the North Sea and in the Baltic Sea they are very rare wanderers.
In the entire range, the pilot whales prefer the open sea and are only relatively rarely seen near the coast. In the Orkney and Shetland Islands as well as the Faroe Islands , however, large schools regularly move along the coasts.
Way of life
A pilot whale needs 50 kilograms of food every day, which consists mainly of cephalopods and, to a much lesser extent, fish . When foraging for food, mostly at night, the whales dive to depths of up to 600 meters. The dives rarely last longer than five to ten minutes. At least in Newfoundland and around the Faroe Islands, their distribution is closely linked to the occurrence of a species of octopus : In Newfoundland it is Ilex unbekanntcebrosus , in the Faroe Islands it is Todarodes sagittatus . The latter species is probably the most important food source for the pilot whales in Europe.
According to current knowledge, there are only very few natural enemies for the pilot whales with the killer whale ( Orcinus orca ) and some large sharks . However, these also pose only a minor threat, as very few pilot whales with wounds could be found.
Pilot whales, like most dolphins, live in groups called schools. These consist of an average of twenty animals, but schools of up to 600 individuals could be observed during the main seasonal occurrence of prey. It is not uncommon for schools of pilot whales to socialize with other small whales , especially bottlenose dolphins or round-headed dolphins . The social structure of the schools is highly developed and the members of the group always follow a lead animal (mostly a dominant male). The name pilot whale is derived from this behavior.
As a rule, the pilot whales travel through the sea at a leisurely speed of around 6 km / h, but in danger they can be up to seven times faster. Outside of the feeding times, the pilot whales swim and breathe largely synchronously, but they spread out in search of food. During the seasonal migrations they come together in large herds of several hundred or even a thousand animals. The migrations themselves are obviously due to the seasonal occurrence of squid, which the whales follow. However, longer hikes are not known.
The communication as well as the echo orientation takes place via an extensive tone repertoire with whistles in the frequency range from three to 18 kilohertz . These whistles are emitted about 14 to over 40 times per minute.
Strandings
Social behavior is sometimes a disadvantage for the pilot whales: If one of the animals is wounded, it swims away in a panic. The entire school follows the injured animal, often ending up in shallow water. Once in the shallow water, the pilot whales can no longer orientate themselves. The mass strandings that occur again and again may also have the same cause. Another theory is that if the leader of a group is affected by environmental factors or disease, the echolocation system fails, causing the whole group to misdirect and lead it to the coast. Anomalies in the earth's magnetic field , ship noise and attacks by sharks are also discussed as causes. Only a minority find their way back into the sea, even if people try to cool the dark animals in the sun by dousing them with sea water.
In New Zealand pilot whales beached repeated in large numbers. The largest mass stranding with 1000 individuals is known from 1918 on the island of Chatham , in 1985 there were 450 in Auckland . In the last 10 years there have been 9 strandings on the Farewell Spit headland , two of them in February 2017: one with 400 animals and one the following day with 200 animals. On December 9, 2017, a single animal was stranded on the beach at Norden- Norddeich in the East Frisian district of Aurich. However, the animal was already dead before it was washed up. On March 23, 2018, about 300 kilometers south of the city of Perth (west coast of Australia), more than 150 whales were driven to the coast. More than half of the animals were already dead.
Reproduction and development
The females become sexually mature at around six to ten years of age, the males only at around twice that age. In European waters, the main mating season is in April and May. Within a school only the dominant males mate with the females. The numerous finds of fighting tracks on male animals indicate rival fights . The animals are obviously polygynous, so a male mates with several females. Long-term relationships do not exist. However, there are several dominant males in a school. Genetic studies have shown that not all young animals in a school come from the males living in this group, so foreign mating occurs relatively often when several schools meet.
Fifteen to sixteen months pass from conception to birth, so the time of birth is in the summer months. The young animals are between 1.60 and 1.90 meters long at birth. They get their first teeth after about two months and complete dentition after about a year. The sex ratio of the newborn whales is slightly shifted in favor of the males. Because of the significantly higher mortality of the males, for animals of reproductive age it is 60 percent females and 40 percent males.
The female takes care of her offspring for an average of four years and is only then ready to mate again. The young animal is suckled in the first two years, but also eats squid from the first year of life. The life expectancy of pilot whales is estimated at an average of 30 to 50 years, the oldest known animal was a female of 57 years.
Systematics
The pilot whale and the short-finned pilot whale ( Globicephala macrorhynchos ) form the genus of the pilot whales ( Globicephala ) within the dolphin family (Delphinidae). The pygmy pilot whale ( Feresa attenuata ), on the other hand, does not belong to this genus, despite its common German name.
The pilot whale was first scientifically described in 1809 by Thomas Stewart Traill as Delphinus melas . In 1828 the whale was granted its own genus Globicephala , which was confirmed in 1898. As a result, the species name was transferred to the female form Globicephala melaena , which is now used synonymously alongside the name Globicephala melas, which is actually valid according to the priority rule of the International Code of Zoological Nomenclature .
Within the pilot whales there are a number of populations that differ slightly in terms of color and size. There is uncertainty as to whether the pilot whales of the southern oceans should be separated from the northern animals as a separate subspecies Globicephala melas edwardii .
Humans and pilot whales
Pilot whales have been hunted by humans for a long time. Great Britain , the USA and Norway have previously caught many pilot whales, but the hunt has mostly been discontinued due to decreasing populations. The pilot whale is still traditionally caught in the Faroe Islands when it gets lost in the narrow fjords of the North Atlantic archipelago. This traditional hunt is called grindadráp . Besides the Faroe Islands, the most intensive pilot whale fishing took place on the coasts of Newfoundland . However, whale populations there collapsed in the early 1970s and whaling ceased. In addition to the traditional hunt for the pilot whale, the animals are often caught as bycatch , especially when fishing for swordfish in Italy and when fishing for mackerel off the USA.
As with many other whales also provides for the existence of the pilot whales pollution of the seas, the main stress. Since they are at the top of the food chain, accumulate in the muscles and the liver and in the kidneys heavy metals such as mercury , lead or cadmium at. The fat-soluble environmental toxins such as polychlorinated biphenyls (PCB) or (now decreasing) dichlorodiphenyltrichloroethane (DDT) and its breakdown product dichlorodiphenyldichloroethene (DDE) are stored in the fat layer . On November 28, 2008, the science magazine New Scientist reported that the Faroe Islands health authorities called for the consumption of pilot whale meat from now on because it is unsuitable for human consumption due to the high concentration of toxins.
The current population of the species in the northern Atlantic is estimated at over 100,000 animals. Accordingly, it is considered frequent and little endangered. Like all small whales, the pilot whale does not fall under the protection provisions of the International Whaling Commission (IWC). However, it is listed in Appendix II of the Washington Convention on Species Protection . International trade in pilot whale products is therefore prohibited. The IUCN lists the species as “ Least Concern ”.
literature
- Mark Carwardine: Whales and Dolphins. Understand, recognize, observe. Gondrom, Bindlach 2005, ISBN 3-8112-2593-6 .
- EH Greig, AH Davenport: A Narrative of the Cruise of the Yacht Maria among the Feroe Islands in the Summer of 1854. Longman, Brown & Green, London 1855 (detailed eyewitness account of a pilot whale hunt in the Faroe Islands in 1854, the travel description appeared anonymously).
- Ralf Kiefner: Whales & Dolphins worldwide. Pacific Ocean, Indian Ocean, Red Sea, Atlantic Ocean, Caribbean, Arctic, Antarctica. Jahr-Top-Special-Verlag Hamburg 2002, ISBN 3-86132-620-5 , (detailed guide to the magazine diving ).
- 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).
- Daniel Robineau, Harald Benke (ed.): Marine mammals. (Handbook of Mammals in Europe; Volume 6). AULA-Verlag, Wiesbaden 1994 (2 volumes)
- 1. - whales and dolphins. ISBN 3-89104-559-X . (detailed textbook)
- Rüdiger Wandrey: The whales and seals of the world. Kosmos, Stuttgart 1997, ISBN 3-440-07047-6 , (identification book that takes into account all mammals of the seas).
- Maurizio Würtz, Nadia Repetto (eds.): Wale and Delphine. Biography of the marine mammals. Jahr, Hamburg 1998, ISBN 3-86132-264-1 , (reference book of the journal diving ).
Individual evidence
- ↑ The crackling background noise comes from the clicks to the echo location.
- ↑ Second whale death in just 24 hours: “Maybe we can save some” orf.at, February 11, 2017, accessed February 11, 2017.
- ↑ North: Dead whale washed up in Norddeich oz-online.de, December 10, 2017, accessed on December 16, 2017.
- ↑ More than 150 whales stranded on the west coast of Australia In: nzz.ch , March 23, 2018, accessed on March 23, 2018.
- ↑ The Faroe Islands health authorities urgently advise against eating whale meat on delphinschutz.org
- ↑ Globicephala melas in the endangered Red List species the IUCN 2018 Posted by: Minton, G. Reeves, R. & Braulik, G., 2018. Accessed August 7 of 2019.
Web links
- Behavior of short-finned pilot whales. on pilot-whales.org
- Pilot Whale Photos and Videos on oceanlight.com (page with photos and videos of pilot whales)
- Photos of pilot whales on wale.info
