Bornean Dolphin
| Bornean Dolphin | ||||||||||||
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Group of Bornean Dolphins |
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| Systematics | ||||||||||||
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| Scientific name of the genus | ||||||||||||
| Lagenodelphis | ||||||||||||
| Fraser , 1956 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Lagenodelphis hosei | ||||||||||||
| Fraser, 1956 |
The Fraser's dolphin or Fraser's dolphin ( Lagenodelphis hosei ) is the only member of the genus Lagenodelphis within the Dolphins (Delphinidae). The species, which has only been known since 1956 , reaches a maximum body length of 2.70 meters and lives mainly in tropical waters.
features
According to estimates based on measurements on a few dozen specimens of this species, the Bornean Dolphin reaches a maximum total length of 2.70 meters and a maximum weight of 210 kilograms. Compared to other dolphin species, the snout is noticeably short, as are the dorsal fin , the pectoral fins ( flippers ) and the tail fluke . The back of these dolphins is black, the belly side is white with a light pink sheen. From the head, more precisely from the base of the melon to the base of the tail, there is a light stripe that widens towards the back and at the same time loses its clarity. Below is a black stripe that starts on the upper part of the snout and then divides into two branches. One of these branches colors the lower lip and runs down to the pectoral fin, where it changes into its black color. The other branch runs over the eye along the side and ends in the area of the anus . The dolphin's jaws have between 34 and 44 teeth in each half of their jaws.
distribution
Very little is known about the actual distribution of the Bornean dolphins. They live mainly in the open sea in the southern areas of the Indian Ocean and in the South Pacific . The first find comes from the seas around Borneo ( Sarawak ). It is frequently seen in the Camotes Sea and the Bohol Strait in the Philippines .
In the Atlantic , three animals were found on the beach of St. Vincent en Mer ( Caribbean Islands ) in 1976 and 17 skulls on the Florida coast in 1986 . In 1984 the only European find so far was made on the coast of Brittany . About 30 animals were seen there, eleven of them stranded. It is also the northernmost sighting of the Borneo dolphins. In 2019 there was also a Bornean dolphin in Europe, and a dead young bull washed up on the island of Gran Canaria . So far nothing is known about the migration of the animals, just as no statements can be made about regional differences, populations or subspecies.
Way of life
According to previous observations, the Bornean Dolphin lives mainly in the high seas . Before South Africa it was found that it occurs mainly in marine regions with a depth of over 1,000 meters. However, stranding shows that the dolphins venture into the coastal regions when hunting for prey.
The diet of the animals consists of various fish , octopus and crustaceans . Obviously, these are mostly prey that can be hunted at night in the shallow water layers down to depths of 250 to 500 meters.
The Bornean dolphins are sociable and usually live in schools of more than 100 individuals. It is not uncommon to see them together with other small whales , especially the round head dolphins ( Grampus griseus ). As with other small whales, sharks and killer whales are the main natural enemies for the Bornean dolphin , but there is no concrete evidence of this so far.
Reproduction and development
Based on examinations of the gonads and the genital system , it is assumed that the animals reach sexual maturity after about 7 years with a body length of 2.30 meters. Nothing is known about the mating times or the duration of pregnancy and lactation.
The young are probably born with a body length of about 80 centimeters, the smallest specimen caught so far was 85 centimeters long and had an umbilical cord that had not yet healed .
Systematics
The Bornean Dolphin was first discovered in 1956 in the form of a single skull in the collection of the British Museum of Natural History in London . The first person to describe it, Fraser, recognized a previously unknown genus in the skull and named it Lagenodelphis due to the similarities with both the common dolphin ( Delphinus delphis ) and the short- snouted dolphin (genus Lagenorhynchus ) .
It was not until 1973 that the external morphology of the dolphins could be elucidated, further investigations showed a closer relationship with the spotted dolphins of the genus Stenella .
Threat and protection
There is no specific use of the Borneo dolphins, occasionally there are reports of animals caught in bycatch by fishermen. Only from the inhabitants of the Lesser Antilles , Indonesia and Sri Lanka are the animals and other dolphin species occasionally caught in a targeted manner. In 1974/75, 16 individuals were specifically captured for keeping in captivity; six of these animals were then released, all others died within 45 days.
Although nothing is known about the exact population figures, the Borneo Dolphin is listed in Appendix II of the Washington Convention on Endangered Species and is therefore internationally protected. It is estimated that compared to other dolphin species it is rarer and only occurs locally.
literature
- FC Fracer: A new Sarawak dolphin. In: The Sarawak Museum Journal. 7, 1956, pp. 478-503.
- J. Niethammer, F. Krapp (ed.): Handbook of mammals in Europe. Volume 6: Marine Mammals. Part 1A: Whales and Dolphins 1 . AULA-Verlag, Wiesbaden 1994.
- WF Perrin, PB Best, WH Dawbin, KC Balcomb: Rediscovery of Fraser's dolphin, Lagenodelphis hosei in Western North Pacific. In: Nature . 241, 1973, pp. 345-350.
- WF Perrin, JS Leatherwood, A. Collet: Fraser's dolphin, Lagenodelphis hosei Fraser, 1956. In: SH Ridgway, RJ Harrison (Eds.): Handbook of marine mammals. Volume 5, London / New York 1994.
swell
- ↑ Rare and relatively unknown Bornean dolphin washed up dead in Pozo Izquierdo , accessed on March 7, 2019
Web links
- Lagenodelphis hosei in the endangered Red List species the IUCN 2006. Posted by: Cetacean Specialist Group, 1996. Retrieved on 12 May, 2006.
