User:Wikiuser5256/Common bottlenose dolphin

Taxonomy

Until 1998, all bottlenose dolphins were considered one species T. truncatus. That year, the Indo-Pacific bottlenose dolphin (T. aduncus) was recognized as a separate species. The two species are thought to have split during the mid-Pleistocene, about 1 million years ago.

Currently, four common bottlenose dolphin subspecies are recognized:

T. t. truncatus, the nominotypical subspecies

T. t. ponticus, or the Black Sea bottlenose dolphin

T. t. gephyreus, or Lahille's bottlenose dolphin

T. t. nuuanu, or the Eastern Tropical Pacific bottlenose dolphin

Bottlenose dolphins along the southern California and Baja California coasts were previously recognized as the Pacific bottlenose dolphin, T. t. gillii, originally described as distinct species T. gillii. The name has since been reclassified as a junior synonym of Tursiops truncatus. Additionally, bottlenose dolphins along the Pacific coast of Central America were described as T. nuuanu in 1911. A review of T. gillii and T. nuuanu specimens supported T. gillii as a synonym of T. truncatus and T. nuaanu as a unique subspecies.

A 2020 study identified four distinct lineages within T. truncatus, each of which could be a distinct subspecies: a lineage native to the coastal regions of the western North Atlantic (off the coast of North America), an offshore lineage found worldwide in pelagic ecosystems, a lineage native to the Mediterranean, and a lineage restricted to the Black Sea (previously described as T. truncatus ponticus). The study noted only weak differentiation between the Black Sea and Mediterranean lineages, and found them to form a sister group to the offshore lineage, indicating that they likely descended from offshore bottlenoses that colonized the Mediterranean and Black Seas. The clade containing the offshore, Mediterranean, and Black Sea populations was sister to the western North Atlantic lineage, indicating deep divergence between the two. An analysis of the morphology, genetics, and evolutionary divergence of the western North Atlantic coastal and offshore ecotypes supported the coastal form as being a distinct species. While the offshore type was retained within T. truncatus, the coastal dolphins are now recognized as Tamanend's bottlenose dolphin (T. erebennus).

Bottlenose dolphins are typically studied and researched due to their accessibility in many different environments for most of the year. This allows for researchers to be able to access them easily. Because of this we know a lot about the ways they communicate, echolocation, and reproduction.

Ecology and behavior

As a very social species, the common bottlenose dolphin lives in groups called pods that typically number about 15 individuals, but group size varies from pairs of dolphins to over 100 or even occasionally over 1,000 animals for short periods of time. Their geographic range dictates a lot of their behaviors including the densities of dolphins while travelling.^{[citation needed]} The types of groups include: nursery groups, juvenile groups, and groups of adult males. Male dolphins tend to form pair bonds, which are the strongest of dolphin bonds, while females stay with their calves for 3–8 years and then tend to stay in social groups. Bottlenose dolphins in Texas typically are in bigger groups and socialize more in the summer than in other months.

Diet

Its diet consists mainly of eels, squid, shrimp and a wide variety of fishes. It does not chew its food, instead swallowing it whole. Dolphin pods often work as a team to harvest schools of fish, though they also hunt individually. Dolphins search for prey primarily using echolocation, which is a form of sonar. Typically, the dolphins will hunt (forage) in the morning and then socialize in the afternoon.

The diet of common bottlenose dolphin pods varies depending on area. Along the U.S. Atlantic coast, the main prey includes Atlantic croakers (Micropogonias undulatus), spot (Leiostomus xanthurus) and American silver perch (Bairdiella chrysoura), while in South Africa, African maasbankers (Trachurus delagoa), olive grunters (Pomadasys olivaceus), and pandora (Pagellus bellottii) are common bottlenose dolphin's typical prey. Their hunting strategies depend on what they are eating; for example, with fish they will circle the school and use their echolocation to feed on them one by one. They can also stun fish using sonar or smash them into corals depending on their speed.

According to combined stomach content and stable isotope analyses in the Gulf of Cádiz, although European conger (Conger conger) and European hake (Merluccius merluccius) are most important prey of common bottlenose dolphins, mass-balance isotopic mixing model (MixSIAR), using δ13C and δ15N shows that Sparidae species; seabreams (Diplodus annularis and D. bellottii), rubberlip grunt (Plectorhinchus mediterraneus), and common pandora, (Pagellus erythrinus) and a mixture of other species including European hake, mackerels (Scomber colias, S. japonicus and S. scombrus), European conger, red bandfish (Cepola macrophthalma) and European pilchard (Sardina pilchardus) are the assimilated diet.

Research indicates that the type and range of fish in a dolphin's diet can have a significant impact on its health and metabolism. Dolphins eat 10–20% of their body weight each day, with pregnant and nursing females eating the most.^{[citation needed]}

Reproduction

Mating behavior of the bottlenose dolphin is polygamous. Although they can breed throughout the year, it mostly occurs in spring, and with a 12 month gestation period mating season and birthing season overlap. Males form alliances, or pair bonds, to seek an estrous female and they attempt to breed the most while keeping other males away from viable females. For a chance to mate with the female, males separate the female from her home range. Females bear a calf every three to six years. After a year-long gestation period, females bear a single calf. Newborn calves are between 0.8 and 1.4 m (2 ft 7 in and 4 ft 7 in) long and weigh between 15 and 30 kg (33 and 66 lb). Typically, the average weight of dolphins is 13.8 kg. The calf's suckling lasts between 18 and 20 months and they are weaned between three and eight years of age. Females typically reproduce every 3 to 6 years when sexual maturity is reached, and there is no recorded menopause in the bottlenose dolphin species. Sexual maturity varies by population, and ranges from 5–14 years of age; sexual maturity occurs between 8 and 13 years for males and 5 to 10 years for females.

Intelligence

Main article: Cetacean intelligence

Common bottlenose dolphins have an encephalization quotient of 5.26, which is even higher than chimpanzees. This more than likely contributes to their high intelligence. Dolphins have large brains which attracts people to study them. They have ability to learn language and comprehend what people are saying to them which is impressive.

Many investigations of bottlenose intelligence include tests of mimicry, use of artificial language, object categorization, and self-recognition. This intelligence has driven considerable interaction with humans. The common bottlenose dolphin is popular in aquarium shows and television programs such as Flipper. It has also been trained for military uses such as locating sea mines or detecting and marking enemy divers, as for example in the U.S. Navy Marine Mammal Program. In some areas, they cooperate with local fishermen by driving fish toward the fishermen and eating the fish that escape the fishermen's nets.

References

1. https://citeseerx.ist.psu.edu/document?repid=rep1&type=pdf&doi=46dd17fdb01a8ea2ff616c0da84f840cc087ffc8#page=87
2. The Bottlenose Dolphin - Google Books
3. The Animal Ethics Reader - Google Books
4. "Behavior Patterns of Bottlenose Dolphins in San Luis Pass, Texas" by E. Elizabeth Henderson and Bernd Würsig