Bottlenose dolphin
| Bottlenose dolphin | ||||||||||||
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Bottlenose dolphin |
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| Tursiops truncatus | ||||||||||||
| ( Montagu , 1821) |
The bottlenose dolphin ( Tursiops truncatus ) is a common type in all the oceans of the dolphins . It is this species that is demonstrated in dolphinariums and made famous through the Flipper series . This has made the bottlenose dolphin the most famous of all dolphins. Although the common dolphin is predominantly found in European waters and the killer whale is also a well-known representative of the dolphins, in Europe the porpoise shapes the image that people have of these animals.
features
The bottlenose dolphin is gray in color and has a lighter belly. It can be between 1.9 and 4 meters long. Its weight is usually between 150 and 300 kg, but it can also reach 650 kg. A newborn calf is 65 to 105 cm tall and 15 to 30 kg. Characteristic is the short snout, which gave this dolphin its English name Bottlenose Dolphin (Bottlenose = bottle nose) because of its shape and which has up to 80 homogeneous teeth. Thanks to its sickle-shaped, dark fin , it can be easily recognized. The bottlenose dolphin, like all other dolphins, sheds the outer skin cells ( peeling ) about every two hours . This permanent regeneration reduces the flow resistance and is also considered in regeneration research for humans and in shipbuilding.
distribution
The bottlenose dolphin is native to all three oceans. It also lives in the Mediterranean and is seen more and more frequently in the North Sea and occasionally in the Flensburg Fjord ( Baltic Sea ), although it was previously preferred to be found in tropical latitudes. This is justified with the rising water temperature, which offers a richer food supply in addition to the warmer water. It often stays near the coast and also gets into shallow bays and lagoons . One of the largest populations of the bottlenose dolphin is found in Shark Bay in Western Australia.
Way of life
Young bottlenose dolphins are born after a gestation period of one year and are about 120 cm long. Dolphin birth can take up to two hours. The young come caudal fin first, which prevents them from drowning at birth. Then the mother pushes it to the surface for its first breath. Surrounded by other members of the group, the mother giving birth is protected from possible shark attacks. There are seldom twins; if they do, they usually do not live long because the breast milk is insufficient. According to observations by Jerome M. Siegel et al. from the University of California at Los Angeles on captive animals, the mother almost never sleeps for up to two weeks after birth. The calf also stays awake during this time, but this lack of sleep does not weaken it; on the contrary, it gains weight. Afterwards, the mother and her calf sleep briefly and the mother does not achieve normal sleep until after a few more weeks. The young stay with the mother for about three years, one year of which is suckled.
Bottlenose dolphins have a lifespan of about 25 years, but they often get much older in captivity. The male dolphin "Moby" died in 2018 in Nuremberg Zoo at the age of 58, while the female dolphin "Nellie" died until she was euthanized in 2014 , who lived in Marineland Florida, is considered to be the oldest known bottlenose dolphin with a death age of approximately 61 years.
Bottlenose dolphins live in close social groups (schools). On average, they swim between 60 and 100 km per day and dive up to 500 m deep. A school consists of two to fifteen individuals, the average is five animals in the Atlantic, but seems to be higher in the Pacific and Indian Oceans. Bottlenose dolphins living in the open sea also have larger schools than the animals near the coast. The hierarchy of a school is headed by an old man. Besides this there are only females and young animals in the association. Young males form their own schools, so-called bachelor associations. The members of the group communicate with each other via whistling sounds; each individual animal has a characteristic recognition tone.
behavior
The "language" of the bottlenose dolphins has been a subject of research for decades. Some scientists believe that after deciphering such a language one could communicate with the dolphins. The predominant scientific doctrine, however, is that bottlenose dolphins have a limited range of signals at their disposal, with which they communicate their identity and how they are to one another.
In addition to the whistling tones, bottlenose dolphins can make high-frequency clicks that are used for echolocation . The sounds are sent forward in a bundled beam. Although bottlenose dolphins have two small ear openings, most of the sound travels through the mouth into the inner ear. This is where the sound is picked up and tells the bottlenose dolphin when it approaches a prey. However, bottlenose dolphins also have good eyesight. With these tools they look for small fish, which are their main prey. They only occasionally eat octopuses and crustaceans.
Bottlenose dolphins are reported to have grandparents overseeing, protecting, and even nursing their grandchildren.
In a study in June 2005 in the journal Proceedings of the National Academy of Science USA appeared, researchers reported the University of Zurich and the University of New South Wales ( Sydney ) that some of the bottlenose dolphins in Western Australia's Shark Bay foraging tools use : They detach sponges from the seabed and put them over their snouts. The sponges serve as a kind of glove to protect their snout when they search for food in the ground. Of the approximately 3,000 dolphins in Shark Bay, only about 30 are so-called Spongers , Dr. Michael Krützen from the Anthropological Institute at the University of Zurich. In order to investigate genetic influences, the DNA of 13 dolphins using sponges was analyzed, as well as the DNA of 172 dolphins who do not use sponges. It has been found that sponge use appears to be passed on in a direct line from mother to daughter. The animals using sponges also showed a significant genetic relationship. The researchers therefore assume that the use of sponges was only invented relatively recently by a female ancestor. It is the first example of a material culture in marine mammals.
Off the Brazilian coast, in a bay near Laguna , a group of free-living, unsupported bottlenose dolphins has been cooperating with local fishermen every autumn for generations. While the fishermen run just a few steps into the water of the Atlantic Ocean and pause there with their cast nets, the bottlenose dolphins drive fish towards the shore from the sea side. Young animals accompany their mothers here, from which it was concluded that in this way the behavior is passed on from generation to generation.
Taxonomy
Whether the bottlenose dolphin is one species or, in truth, needs to be divided into two or three species is controversial. Some zoologists name these three types:
- Atlantic bottlenose dolphin ( Tursiops truncatus )
- Indo-Pacific Bottlenose Dolphin ( Tursiops aduncus )
- Pacific Bottlenose Dolphin ( Tursiops gillii )
While most zoologists lately considered these to be at most subspecies of a single species, Dale W. Rice has in his standard work Marine Mammals of the World. Systematics and Distribution (1998) saw T. aduncus as an independent species, but T. gillii was classified as a subspecies of T. truncatus .
Bottlenose dolphins living in the Black Sea are a subspecies of the Atlantic bottlenose dolphin and are listed as Tursiops truncatus ponticus .
People and bottlenose dolphins
The bottlenose dolphin is not endangered because it is numerous and adaptable in its extensive range. Bottlenose dolphins have been hunted in different parts of the world for their meat and trans. Today such hunting still takes place in West Africa, Sri Lanka, Indonesia and Japan. European countries as well as the USA stopped hunting bottlenose dolphins in the middle of the 20th century. Bottlenose dolphins, on the other hand, often get caught in fishing nets and drown; far more bottlenose dolphins die in this way than through active hunting.
When experimenting with different species of dolphins, it was soon found that the bottlenose dolphin was the most suitable for performing tricks in shows. However, there has recently been more and more criticism of the keeping in dolphinariums , as it is controversial whether bottlenose dolphins can be kept under species-appropriate conditions. There are two dolphinariums in Germany, one in Duisburg Zoo and one in Nuremberg Zoo . The dolphinarium in the Allwetterzoo Münster was closed in February 2013 because there was no money for a new building.
Bottlenose dolphins are also becoming increasingly important in other areas. In dolphin therapy he is supposed to help support autistic and handicapped children. Bottlenose dolphins are trained to find sea mines in both the United States and Russia .
The film The Bay from 2009 describes the annual rounding up and killing of these animals in Japanese Taiji .
Individual evidence
- ^ Dolphins in front of Flensburg. In: Spiegel online. February 18, 2016.
- ↑ Oliver Manlik, Jane A. McDonald, Janet Mann, Holly C. Raudino, Lars Bejder: The relative importance of reproduction and survival for the conservation of two dolphin populations . In: Ecology and Evolution . 2016, ISSN 2045-7758 , doi : 10.1002 / ece3.2130 ( wiley.com [accessed May 6, 2016]).
- ↑ Ceta Base | Captive Cetacean Database - Duisburg Zoo • Germany. Retrieved August 11, 2020 (American English).
- ↑ Marineland Florida: Dolphin Facts. ( Memento of April 18, 2012 in the Internet Archive ) on: marineland.net , February 2012.
- ↑ Ceta Base. Retrieved August 11, 2020 .
- ^ JR Carey, C. Gruenfelder: Population Biology of the Elderly. In: KW Wachter, CE Finch (Ed.): Between Zeus and the Salmon: The Biodemography of Longevity. Natl. Acad. Press, Washington, DC 1997, pp. 127-160. Quoted from Ronald D. Lee: Rethinking the evolutionary theory of aging: Transfers, not births, shape senescence in social species. In: PNAS . Volume 100, No. 16, 2003, pp. 9637-9642. doi: 10.1073 / pnas.1530303100
- ↑ Michael Krützen et al .: Cultural transmission of tool use in bottlenose dolphins. In: PNAS. Volume 102, No. 25, 2005, pp. 8939-8943. doi: 10.1073 / pnas.0500232102
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↑ FG Daura-Jorge et al .: The structure of a bottlenose dolphin society is coupled to a unique foraging cooperation with artisanal fishermen. In: Biology Letters. Online advance publication of May 2, 2012, doi: 10.1098 / rsbl.2012.0174
sciencemag.org ( page no longer available , search in web archives ) Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. from May 1, 2012: Clues to an Unusual Alliance Between Dolphins and Fishers. "Bottlenose Dolphins in Laguna Requesting a Throw Net"
- ↑ WDSF: Dolphinarium Münster is closed
Web links
- Tursiops truncatus in the endangered Red List species the IUCN 2006. Posted by: Cetacean Specialist Group, 1996. Retrieved on 8 May, 2006.