Bottlenose dolphin ( Tursiops truncatus )
|Gray , 1821|
The dolphins or dolphins (Delphinidae) belong to the toothed whales (Odontoceti) and are therefore mammals (Mammalia) that live in the water ( marine mammals ). Dolphins are the most diverse and with around 40 species the largest family of whales (Cetacea). They are common in all seas, some species are also found in rivers.
Dolphins are usually between one and a half and four meters long, the killer whale as the largest dolphin even reaches eight meters. They have a streamlined body that is adapted to the high swimming speeds. There is a round organ in the head, the melon . It plays a role in echolocation . In many species, the jaws are clearly set off and form an elongated beak. The snout can contain many teeth in several species.
The dolphins' brains are large and complex, which is why many zoologists consider them among the most intelligent animals. But there is also the controversial theory that the large brain is merely an adaptation to life in the water and serves to better regulate the loss of heat to the water. This theory is based on the fact that the dolphins' brains have a large number of glial cells and, in relation to this, few nerve cells . It is believed that the glial cells help with thermal insulation. Dolphins can quickly learn sequences of movements and reactions to acoustic stimuli, but with abstract objects such as triangles or squares, their learning speed is slower than that of pigeons and rats. Some ethicists, however, speak of dolphins as individuals who, according to this definition, even have personality rights, due to their supposedly high mental capacity and emotional intelligence.
The body color is usually made up of black to white, with the underside usually being lighter and the back being clearly defined by a darker color, the cape . The color exceptions include the bluish blue-white dolphin and the brown-yellow common dolphin . In addition, the species are distinguished by lines and fields in different colors and contrasts.
Dolphins have very good hearing and sight. While external ear openings exist, these are unlikely to be functional. Sounds reach the inner ear via the lower jaw and middle ear. Your hearing range extends in frequencies of up to 220 kHz and you can perceive sounds far into the ultrasonic range. The eyes are mainly adapted to seeing underwater, but they also function well outside of the water. Echolocation by means of ultrasound plays a major role in perception.
Dolphins differ from other toothed whales in the following features: fusion of the first two cervical vertebrae, a smaller number of ribs, fusion of the two halves of the lower jaw to a maximum of one third of the jaw length and blunt teeth.
All dolphins shed the outer skin cells about every two hours ( peeling ). This permanent regeneration reduces the flow resistance and is also considered in regeneration research for humans and in shipbuilding. The skin of the dolphins promotes their rapid swimming through low flow resistance over fine relief and vortex damping through plasticity, typical for the skin of whales .
Dolphins are fast swimmers, they can reach speeds of up to 55 kilometers per hour. They often jump out of the water, sometimes performing acrobatic figures (e.g. the spinner dolphin ). Such jumps are interpreted as game behavior and communication. In addition, the jumps also enable the dolphins to move around with less effort. Jumps may also help in the search for feeding places, as dolphins can use them to orient themselves to groups of gulls. When hunting, they can dive up to 300 meters for 15 minutes; however, most dives last a few minutes. Dolphins are known to approach ships to ride the waves.
Dolphins are social animals that live together in groups. These so-called schools can temporarily unite to form groups of over 1000 animals in places with plenty of food. The individuals communicate with one another with clicks, whistles, chattering and other noises. But they also communicate with their fellow species through physical contact.
With high-frequency tones, they are also able to perceive their environment by means of echolocation .
Membership in the groups is not very stable and changes between them are common. Nevertheless, the animals can develop strong bonds with each other, which is particularly evident in the support they provide for injured or sick conspecifics.
Dolphins sleep by letting one side of their brain fall asleep and staying awake with the other. This will maintain breathing. In addition, one eye always remains open while sleeping so that the environment and possible attackers can be seen. The dolphins' mobility is limited during sleep.
Like all whales, dolphins only give birth to one cub at a time. The gestation period is on average one year, but varies from species to species. The calves stay with their dams for up to six years; they begin to look for food independently at the age of a few months.
Findings from a marine biology research team have been suggesting since 2006 that bottlenose dolphins can identify themselves using personal whistling sounds. In this way, the animals not only identify themselves individually, but are also "called" by members of their group with this whistling sound and also answer it. This sound is defined by the sound sequence and not by the characteristics of the voice and is therefore used like a name, a phenomenon that is unique in the animal kingdom to this day.
Dolphins are fast predators that actively hunt their prey. They find their prey by echolocation and have a specialized organ for this, the melon . In general, dolphins have uniformly conical teeth that are only used to hold prey in place. The caught fish or squids are almost always eaten in one piece. The teeth are adapted to the respective prey: species with a large number of teeth feed mainly on fish, while species with fewer teeth mostly hunt squids. Some dolphins sometimes catch crustaceans . The killer whale is the only dolphin to feed on other marine mammals such as seals or other whale and dolphin species. Some dolphins use cooperative hunting strategies, with a school of prey being circled by the whole school or driven to the coast.
Suckling works like all whales: the mother dolphin actively injects the high-fat milk through the muscles of the mammary glands into the boy's mouth, as the boy's mouth has no lips with which to suckle.
The internal system of the dolphins is controversial. Several subfamilies were introduced on the basis of morphological differences, but these are not likely to correspond to the actual relationships of descent. The position of the Irrawaddy dolphin was also controversial, sometimes completely removed from the dolphins and classified with the gudgeon whales ; however, according to genetic studies, he is one of the dolphins.
A distinction is made between the following genera and species (sorted alphabetically):
- Genus black and white dolphins ( Cephalorhynchus )
- Genus Delphinus
- Genus Feresa
- Little pilot whale ( Feresa attenuata )
- Genus pilot whales ( Globicephala )
- Genus Grampus
- Round-headed dolphin ( Grampus griseus )
- Genus Lagenodelphis
- Borneo dolphin ( Lagenodelphis hosei )
- Genus short-snouted dolphins ( Lagenorhynchus )
- Genus smooth dolphins ( Lissodelphis )
- Genus Orcaella
- Genus Orcinus
- Killer whale or orca ( Orcinus orca )
- Genus Peponocephala
- Broad-billed dolphin ( Peponocephala electra )
- Genus Pseudorca
- Little killer whale ( Pseudorca crassidens )
- Genus Sotalia
- Genus Sousa
- Genus Fleckendelfine ( Stenella )
- Genus Steno
- Rough-toothed dolphin ( Steno bredanensis )
- Genus Tursiops
In the article Systematics of Whales there is a comparison of the distribution area, the frequency and threat, as well as the size of the different dolphins.
Genetic studies reveal different groups of species. The genus Orcaella is likely to be closely related to the killer whale. Likewise, a generic group of short-nosed, pilot whale-like dolphins (genera pilot whale ( Globicephala ), dwarf pilot whale ( Feresa ), round-headed dolphin ( Grampus ), broad -beaked dolphin ( Peponocephala ) and killer whale ( Pseudorca )) is likely. In return, the genera Lagenorhynchus and Stenella could be polyphyletic , that is, summarize only outwardly similar but not closely related species. It is possible that not only these two genera, but also Tursiops , Lagenodelphis and Sousa are poly- or paraphyletic and would ultimately have to be synonymous with the generic name Delphinus (under which the species were usually first described). There is no generally recognized internal system of dolphins.
Dolphins and people
If, as David Fouts suspects, the nahiru (mostly translated as "sea horse") mentioned in the annals of Aššur-bēl-kala is actually a dolphin, this is the earliest written record of a dolphin. The Assyrian king sailed the Mediterranean in a ship from Arwad and "slew a nahiru on the great sea". Two nahiru were also among the guardian figures of Aššur-bēl-kalas palace in Aššur .
Of all the dolphin species, the bottlenose dolphin ( Tursiops truncatus ) is the best known. It is most often kept in dolphinariums and has been successfully bred there for years. The keeping of dolphins in dolphinariums is controversial . a. because a tank never has the standards of a sea and the attitude prevents natural social and hunting behavior. There are also ethical concerns about keeping dolphins. Scientists attribute dolphins, like primates, among others, the ability to see themselves in the mirror. The intelligence of whales also seems to be considerably higher than previously assumed. The largest dolphin is the orca , which is popular because of its popularity as a crowd puller.
Because of their high learning ability, bottlenose dolphins are kept by the military in the USA and Russia, for example to install sea mines on enemy ships or to defuse mines. That dolphins were trained to kill enemy combat divers is probably a legend that in the wake of the thriller of the Dolphin Day (The Day of the Dolphin) by Mike Nichols has arisen from the year 1973rd
Dolphins are also used for dolphin therapy for seriously ill and autistic people. Because of their playfulness, they are particularly suitable for this. Usually the patients hold on to the dolphin's dorsal fin and are pulled through the water by it. In many patients, this releases blockages. The study by the University of Würzburg in cooperation with the Nuremberg Zoo is probably the best known in the German-speaking countries. However, dolphin therapy is also controversial, as the same effect can usually be achieved with other animals at significantly lower costs. In addition, the known studies are accused of methodological deficiencies.
Threat from dolphin hunting and fishing nets
Dolphin hunting takes place through the Faroe Islands at Grindadráp (here with dolphins mainly white-sided dolphins ) and Japan . The 2009 Oscar-winning documentary The Bay made famous the city of Taiji , where more than a thousand dolphins are caught and killed every year.
Also fishing nets are a threat to the animals. Either they are thrown overboard as “worthless” bycatch and perish injured, or they get tangled in the net and drown. It is estimated that in 2019 alone, more than 11,000 dolphins died as bycatch off the coast of France as a result of fishing. That is why pingers are being negotiated to protect animals in Europe.
The aquatorium between the islands of Cres and Lošinj in Croatia was officially declared a dolphin sanctuary in 2006 . It is thus one of the first sanctuaries in the world for dolphins and the first in the Mediterranean . The organization Blue World , which has its base in the nearby coastal town of Veli Lošinj and is actively committed to the protection of dolphins and other marine animals, provides information about the correct behavior when sighting dolphins, how to steer boats, etc. v. m. There is also a small dolphin museum in Veli Lošinj. Every year in August there is a big dolphin festival in the village, which tries to make the population aware of marine animals and nature conservation.
Dolphins in mythology
In Greek mythology , dolphins appear as an animal of the goddess Demeter . When the sun god Apollo was born on an island in the middle of the sea, he was then brought ashore by a dolphin. The dolphin was raised into the sky as a constellation because it helped Poseidon win the hand of the sea nymph Amphitrite . In many ancient Greek depictions the Nereids rode on the backs of dolphins. According to legend , the singer Arion from Lesbos , thrown overboard out of envy , was saved by dolphins.
Due to the appreciation of the dolphin and its extremely positive occupation in mythology, it was also used as a heraldic animal in the heraldry of the European Middle Ages . The most momentous was the corresponding use by the Counts of Vienne , which ultimately led to the French crown prince using the title Dauphin , or “dolphin”, for centuries .
Dolphins also play a significant role in modern mythology and esotericism . In particular, the American neurophysiologist John Cunningham Lilly , who conducted obscure experiments with isolation tanks and LSD in the sixties and seventies and claimed to be able to communicate with dolphins in this way, made dolphins a symbolic animal in the esoteric and hippie movement. In the fifties and sixties, Lilly had initially made scientifically recognized contributions to communication and the behavioral physiology of dolphins.
Dolphins in Literature
Dolphins are popular characters in literature and film. A well-known novel is A rational animal (construction Tb 2003, ISBN 3-7466-1222-5 ) by Robert Merle . The character Flipper from the television series of the same name is also very well known. In Take Care and Thank You for the Fish by Douglas Adams we experience the mystery of a new earth, similar to the old one, but this time without dolphins.
In David Brin's novel Star flood dolphins are the species Tursiops and Steno , in addition to chimpanzees , by man using genetic modification to a higher consciousness and intelligence level "charged" been (Engl. Uplifting ). In Brin's uplift universe , they have an intelligence and position in society that is comparable to humans.
Scheffel sings about dolphins in front of Salerno in the song The Dolphin .
Dolphins, on the other hand, play a hostile and malicious role in the main work of the Sicilian author Stefano D'Arrigo . In Horcynus Orca , the genus serves as the consistent antagonist of the fishermen, as a cipher for Italian fascism and a mythical figure of death.
The International Year of the Dolphins was proclaimed in 2007.
The swimming style of butterfly swimming was formerly known as "dolphin swimming". “Dolphin flight” is a metaphorical term for a flight strategy that is used in gliding and is similar to the swimming style of dolphins.
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