Bottlenose dolphins are aquatic mammals in the genus Tursiops. They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus definitively contains two species: the common bottlenose dolphin (Tursiops truncatus) and the Indo-Pacific bottlenose dolphin (Tursiops aduncus). Others, like the Burrunan dolphin (Tursiops (aduncus) australis), may be alternately considered their own species or be subspecies of T. aduncus. Bottlenose dolphins inhabit warm and temperate seas worldwide, being found everywhere except for the Arctic and Antarctic Circle regions. Their name derives from the Latin tursio (dolphin) and truncatus for their characteristic truncated teeth.
Numerous investigations of bottlenose dolphin intelligence have been conducted, examining mimicry, use of artificial language, object categorization, and self-recognition. They can use tools (sponging; using marine sponges to forage for food sources they normally could not access) and transmit cultural knowledge from generation to generation, and their considerable intelligence has driven interaction with humans. Bottlenose dolphins gained popularity from aquarium shows and television programs such as Flipper. They have also been trained by militaries to locate sea mines or detect and mark enemy divers. In some areas, they cooperate with local fishermen by driving fish into their nets and eating the fish that escape. Some encounters with humans are harmful to the dolphins: people hunt them for food, and dolphins are killed inadvertently as a bycatch of tuna fishing and by getting caught in crab traps.
Scientists have been long aware of the fact that the Tursiops dolphins might consist of more than one species, as there is extensive variation in color and morphology along its range. In the past, most studies used morphology to evaluate differences between and within species, but in the late 20th century, combining morphological and molecular genetics allowed much greater insight into this previously intractable problem. Since the late 1990s and early 2000s, most researchers acknowledged the existence of two species: the common bottlenose dolphin (T. truncatus), found in coastal and oceanic habitats of most tropical to temperate oceans, and the Indo-Pacific bottlenose dolphin (T. aduncus), that lives in coastal waters around India, northern Australia, South China, the Red Sea, and the eastern coast of Africa.
In 2011, a third distinct species was described, the Burrunan dolphin (T. (aduncus) australis), found in the Port Phillip and Gippsland Lakes areas of Victoria, Australia, after research showed it was distinct from T. truncatus and T. aduncus, both in morphology and genetics. Also, evidence has been accumulating to validate the existence of a separate species, Lahille's bottlenose dolphin, T. gephyreus, that occurs in coastal waters of Argentina, Uruguay and southern Brazil. The Society for Marine Mammalogy's Committee on Taxonomy, presently recognizes only two species, T. truncatus and T. aduncus, and two subspecies: the Black Sea bottlenose dolphin (T. t. ponticus), that lives in the Black Sea, and Lahille's bottlenose dolphin (T. t. gephyreus). Other sources also accept the Pacific bottlenose dolphin (T. t. gillii or T. gillii), that inhabits the Pacific, and has a black line from the eye to the forehead.[failed verification] The IUCN, on their Red List of endangered species, also recognises only two species of bottlenose dolphins. The American Society of Mammalogists also recognizes only two species; while acknowledging the studies describing T. australis, it classifies it within T. aduncus.
Much of the discussion and doubts about its taxonomy is related to the existence of two ecotypes of bottlenose dolphins in many part of its distribution. The two ecotypes of the common bottlenose dolphin within the western North Atlantic are represented by the shallower water or coastal ecotype and the more offshore ecotype. Their ranges overlap, but they have been shown to be genetically distinct. They are not currently described, however, as separate species or subspecies. In general, genetic variation between populations is significant, even among nearby populations. As a result of this genetic variation, other distinct species currently considered to be populations of common bottlenose dolphin are possible.
Some recent genetic evidence suggests the Indo-Pacific bottlenose dolphin belongs in the genus Stenella, since it is more like the Atlantic spotted dolphin (Stenella frontalis) than the common bottlenose dolphin. However, more recent studies indicate that this is a consequence of reticulate evolution (such as past hybridization between Stenella and ancestral Tursiops) and incomplete lineage sorting, and thus support T. truncatus and T. aduncus belonging to the same genus.
Bottlenose dolphins have been known to hybridize with other dolphin species. Hybrids with Risso's dolphin occur both in the wild and in captivity. The best known hybrid is the wholphin, a false killer whale-bottlenose dolphin hybrid. The wholphin is fertile, and two currently live at the Sea Life Park in Hawaii. The first was born in 1985 to a female bottlenose. Wholphins also exist in the wild. In captivity, a bottlenose dolphin and a rough-toothed dolphin hybridized. A common dolphin-bottlenose dolphin hybrid born in captivity lives at SeaWorld California. Other hybrids live in captivity around the world and in the wild, such as a bottlenose dolphin-Atlantic spotted dolphin hybrid.
The bottlenose dolphin weighs an average of 300 kg (660 pounds), but can range from 150 and 650 kg (330 and 1,430 lb). It can reach a length of just over 4 meters (13 feet). Its color varies considerably, is usually dark gray on the back and lighter gray on the flanks, but it can be bluish-grey, brownish-grey, or even nearly black, and is often darker on the back from the rostrum to behind the dorsal fin. This is called countershading and is a form of camouflage. Older dolphins sometimes have a few spots.
The flukes (lobes of the tail) and dorsal fin are formed of dense connective tissue and do not contain bone or muscle. The dorsal fin usually shows phenotypic variations that help discriminate among populations. The animal propels itself by moving the flukes up and down. The pectoral flippers (at the sides of the body) are for steering; they contain bones homologous to the forelimbs of land mammals. A bottlenose dolphin discovered in Japan has two additional pectoral fins, or "hind legs", at the tail, about the size of a human's pair of hands. Scientists believe a mutation caused the ancient trait to reassert itself as a form of atavism.
By contrast, a bottlenose's sense of smell is poor, because its blowhole, the analog to the nose, is closed when underwater and it opens only for breathing. It has no olfactory nerves or olfactory lobe in the brain. Bottlenose dolphins are able to detect salty, sweet, bitter (quinine sulphate), and sour (citric acid) tastes, but this has not been well-studied. Anecdotally, some individuals in captivity have been noted to have preferences for food fish types, although it is not clear if taste mediates this preference.
Other communication uses about 30 distinguishable sounds, and although famously proposed by John C. Lilly in the 1950s, no "dolphin language" has been found. However, Herman, Richards, and Wolz demonstrated comprehension of an artificial language by two bottlenose dolphins (named Akeakamai and Phoenix) in the period of skepticism toward animal language following Herbert Terrace's critique.
At least some wild bottlenose dolphins use tools. In Shark Bay, off Western Australia, dolphins place a marine sponge on their rostrum, presumably to protect it when searching for food on the sandy sea bottom. This has only been observed in this bay (first in 1997), and is predominantly practiced by females. A 2005 study showed mothers most likely teach the behavior to their offspring, evincing culture (behavior learned from other species members).
Mud plume feeding is a feeding technique performed by a small community of bottlenose dolphins over shallow seagrass beds (less than 1 m) in the Florida Keys in the United States. The behavior involves creation of a U-shaped plume of mud in the water column and then rushing through the plume to capture fish.
Along the beaches and tidal marshes of South Carolina and Georgia in the United States, bottlenose dolphins cooperatively herd prey fish onto steep and sandy banks in a practice known as "strand feeding". Groups of between two and six dolphins are regularly observed creating a bow wave to force the fish out of the water. The dolphins follow the fish, stranding themselves briefly, to eat their prey before twisting their bodies back and forth in order to slide back into the water. While initially documented in South Carolina and Georgia, strand feeding has also been observed in Louisiana, Texas, Baja California, Ecuador, and Australia.
Near Adelaide, in South Australia, several bottlenose dolphins "tail-walk", whereby they elevate the upper part of their bodies vertically out of the water, and propel themselves along the surface with powerful tail movements. Tail-walking mostly arises via human training in dolphinaria. In the 1980s, a female from the local population was kept at a local dolphinarium for three weeks, and the scientist suggests she copied the tail-walking behavior from other dolphins. Two other wild adult female dolphins copied it from her, and the behaviour has continued through generations until 2022. 041b061a72