White-beaked dolphin
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White-beaked dolphins ( Lagenorhynchus albirostris ) |
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| Lagenorhynchus albirostris | ||||||||||||
| Gray , 1846 |
The white-beaked dolphin ( Lagenorhynchus albirostris ) is a marine mammal from the genus of the short-beaked dolphin ( Lagenorhynchus ). It only lives in the North Atlantic , where it represents the representative of its genus with the northernmost distribution area.
features
With a size of 1.10 to 1.20 meters at birth and an average height of 2.75 meters in adulthood, the white-beaked dolphin is one of the larger dolphins . The animals reach a weight of up to 350 kilograms, males are slightly larger than females.
The white-beaked dolphin is characterized by its short, strong, cream-colored snout, from which the name of this species goes back. This is clearly anatomically separated from the head. Another distinct feature is the sickle-shaped dorsal fin, which is curved backwards and is known as the fin . The pectoral fins or flippers are very broad at the base and slightly rounded at the top. The caudal stalk is keeled on the abdomen and back, the rear edge of the caudal fin or fluke is concave and rounded and moderately notched.
The back and sides of the whale are dark gray to black, with two light gray fields on each side that can also merge. All fins are also black, but the belly and throat are white. However, there is a high degree of variability in terms of coloration . The underside of the fluke can be speckled with white spots or a dark streak from the mouth to the pectoral fin. The shape and the merging of the side spots in particular vary greatly.
With 88 to 93 vertebrae, the animals have the largest number of vertebrae of all whales. The number of conical teeth with 22 to 25 pairs per jaw is relatively low compared to other dolphins.
The white-beaked dolphin is often confused with the white-sided dolphin ( Lagenorhynchus acutus ), although this is generally found further north. Furthermore, the white-beaked dolphin is usually larger and does not have yellow stripes on its side.
distribution
The white-beaked dolphin is only distributed in the North Atlantic and is therefore an endemic species. The range extends in a band over the ocean from Cape Cod , the mouth of the Saint Lawrence River and southern Greenland in the west, around Iceland , across to northern France and Svalbard in the East.
In European waters it is mainly found around Iceland, but it is also often found off Norway , Great Britain , Ireland , Germany , the Netherlands and Denmark . Regular sightings also come from the western Baltic Sea . So far, only a few sightings and strandings are known from northern France. No such events are known from the marine areas south of the English Channel , which is why it can be assumed that the dolphin probably does not occur there.
Like other whales, the white-beaked dolphins migrate northwards in spring, often to the edge of the pack ice . In winter, the animals stay in more moderate areas of the North Atlantic.
Way of life
The white-beaked dolphins live mainly in the pelagic area of the waters, but they also come to the coasts and in the coastal areas. When hunting and during the mating season, the white-beaked dolphins appear in schools of 6 to 30 animals, but groups of up to 1,500 animals have also been observed. Mixed groups with other small whales , especially the bottlenose dolphin ( Tursiops truncatus ) and the white-sided dolphin , as well as large whales such as the fin whale ( Balaenoptera physalus ) have also been spotted.
The marine mammals feed mainly on schooling fish up to the size of mackerel and squid . They also occasionally ingest prey that live on the sea floor, such as various crustaceans . Sharks and the great killer whale ( Orcinus orca ) are likely to be mentioned as enemies, especially among the young dolphins , but there is no evidence for this.
The size of the population is estimated at several hundred thousand specimens, with the animals occurring more frequently in the east of their range than in the west.
Reproduction and development
Based on the animals examined, it is assumed that sexual maturity begins at a length of around 2.50 meters. However, this cannot be carried over to old age, as growth studies are lacking.
Due to the accumulation of young animals stranded in July to September, it is assumed that the time of birth falls in midsummer, but nothing is known about the gestation period and the mating times as well as the mating areas.
The birth length of the white-beaked dolphins is about 1.20 meters, but neither the growth rate nor the maximum age of the animals are known.
Systematics
The white-beaked dolphin was described as the first species of the genus Lagenorhynchus by John Edward Gray in 1846 .
Four other species are also classified in the same genus of short-snouted dolphins. It is the white-sided dolphin ( Lagenorhynchus obliquidens ), the Dusky Dolphin ( Lagenorhynchus obscurus ), the Peale's Dolphin ( Lagenorhynchus australis ) and hourglass dolphin ( Lagenorhynchus cruciger ). Phylogenetic studies on this group do not yet exist.
Threat and protection
The white-beaked dolphin is classified as a species of very little economic importance. There have been occasional catches of the animals in the past through fishing and whale catches on the coasts of Canada , Greenland and Scandinavia , but they were mostly not targeted at these whales. In the 19th century, white-beaked dolphins were apparently regularly driven into bays by Indians in eastern Canada and killed there. In 1983 five animals were caught alive for the Mystic, Connecticut aquarium . There are no other reports of live catches.
As with many other whales, the pollution of the oceans is also a burden for the white-beaked dolphins, but exact figures do not exist. Various fat-soluble environmental toxins such as polychlorinated biphenyls (PCB) and heavy metals such as lead , cadmium and mercury were found in its fat layer . Also avoid heptachlor epoxide , the degradation product of the once widespread but now banned in Germany pesticide heptachlor could be detected for this species.
Like all small whales, the white-beaked dolphin does not come under the protection regulations of the International Whaling Commission (IWC). However, it is listed in Appendix II of the Washington Convention on Endangered Species , and international trade in corresponding dolphin products is accordingly prohibited. In addition, there are special laws in various states that regulate the hunting and trade in dolphins.
literature
- Not so Galatius, Carl Christian Kinze: Lagenorhynchus albirostris (Cetacea: Delphinidae). Mammalian Species 48 (933), Aug. 5, 2016; Pp. 35-47. DOI: 10.1093 / mspecies / sew003
- J. Niethammer, F. Krapp (ed.): Handbook of mammals in Europe. Volume 6. Marine mammals, T 1a. Wale und Delphine 1. Aula, Wiesbaden 1994, ISBN 3-89104-559-X
- 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
- Mark Carwardine: Whales and Dolphins. Delius Klasing, Bielefeld 2008, ISBN 978-3768824736
- Mark Carwardine: Dolphins - Biology, Distribution, Observation in the Wild. Naturbuch, Augsburg 1996, ISBN 3-89440-226-1
- Ralf Kiefner: whales and dolphins worldwide. Year Top Special, Hamburg 2002, ISBN 3-86132-620-5
- Gérard Soury: The great book of the dolphins. Delius Klasing, Bielefeld 1997, ISBN 3-7688-1063-1
- Maurizio Würtz, N. Repetto: Underwater World. Dolphins and Whales. White Star Guides, Vercelli 2003, ISBN 88-8095-943-3
- Tsuneo Nakamura: Dolphins. Chronicle Books, San Francisco 1997, ISBN 0-8118-1621-4
Web links
- Lagenorhynchus albirostris in the endangered Red List species the IUCN 2006. Posted by: Cetacean Specialist Group, 1996. Retrieved on 12 May, 2006.