Latin name

Tursiops truncatus

Other names

Atlantic bottlenose dolphin

Identification

The moderately developed "beak" is clearly separated from the convex frontal-nasal (fat) pad. The skull reaches a length of 58 cm. The palate is flat, without lateral furrows. The teeth are strong, conically pointed, 6-10 mm thick, 19-28 pairs at the top and 1-3 pairs fewer at the bottom. They are arranged in such a way that there is space between them. When they close, the teeth in the upper row fall into the spaces between the teeth in the lower row. The lower jaw is slightly longer than the upper jaw. 

Dolphins have no sweat glands and their bodies are insulated by a layer of fat. They therefore exchange heat with water through their pectoral, dorsal and tail fins. Dolphins that are washed ashore often die from overheating; fins that overheat without water can permanently stop functioning, so dolphins are specially wetted and cooled during transport.

In captivity, they breathe 1-4 times per minute, with an exhalation immediately followed by an inhalation, lasting a fraction of a second, followed by an interval of 15-30 seconds during which the air is in the dolphin's lungs. The heart beats 80-140 (average 100) times per minute. It can reach speeds of up to 40 km/h and jump up to 5 metres.

Bottlenose dolphins have a complex vocal apparatus, consisting of three pairs of air sacs connected to the nasal canal. To communicate with each other, they emit communication signals with a frequency of between 7 and 20 kHz: whistling, barking (to track prey), mewing (to feed), clapping (to intimidate their relatives), etc. They can also communicate with each other. When searching for prey and orientating themselves underwater, they emit echolocation clicks, similar to the creak of rusty door hinges, at a frequency of 20-170 kHz. Scientists have recorded 17 communication signals in adult afalines and only 6 in juveniles. Obviously, the system of signals becomes more complex with age and individual experience. 

Bottlenose dolphins, like all cetaceans, sleep near the surface of the water, usually at night, and during the day only after feeding, periodically opening their eyelids for 1-2 s and closing them for 15-30 s.  In sleeping dolphins, one hemisphere of the brain alternately sleeps while the other is awake.

Features of fish fins

Dorsal fin high, with broad base, semilunarly notched posteriorly. Pectoral fins broad at the base, pointed towards the end, convex along the anterior margin and concave along the thin posterior margin.

Fish colouring

The body colour is dark brown on top, light underneath (from grey to white); the pattern on the sides of the body is variable, often not expressed at all. There are 2 colour groups in the Black Sea. Type A is characterised by a more or less clear boundary between the dark colouring of the back and the white colouring of the belly, and by the fact that in the dark field of the central part of the body there is a light angle, the tip of which faces the dorsal fin. In type B, the pigmented upper side of the body does not have a sharp border with the lower side; it is represented by a more or less blurred straight, wavy or broken line without a light angle on the dorsal fin.

Distribution

Widespread in the temperate and warm waters of the world's oceans. In the Atlantic lives from the latitude of southern Greenland and Norway to Uruguay, Argentina and South Africa, including the Baltic, Black, Mediterranean, Caribbean and Gulf of Mexico Seas. In the Indian Ocean it lives from its northern coasts, including the Red Sea, south to the latitude of South Africa, South Australia. In the Pacific Ocean it is found from Japan, the Kuril Islands, Oregon to Tasmania, New Zealand and Argentina.

Habitat

Bottlenose dolphins can be found in coastal and offshore waters around the world. They prefer warm temperate waters to colder climates.

Size

Length 2.3-3 m, rarely up to 3.6 m. Weight usually 150-300 kg. Males are 10-20 cm larger than females.

Behavior

Lives sedentary or migrates in small flocks and may make annual travel of more than several thousand miles (about 3000). Can live for at least 40 years, and some females outlive males by 60 years or more.

Food and feeding habits

The animal's tendency towards the coastal zone is explained by the benthic nature of its diet. It dives to depths of up to 90m in the Black Sea and up to 150m in the Mediterranean in search of food. When hunting for fish, they move irregularly, jerkily, with frequent sharp turns. Their breaths last from a few seconds to 6-7 minutes, up to a maximum of fifteen minutes. They are most active during the day.

The main food is fish of various species. Thus, the diet of the Black Sea afalina consists of the following fish species: horse mackerel, anchovy, haddock, flounder, mullet, loban, grey mullet, umbrina, hamsa, pelamida, skate, ray, as well as octopus, shrimp, shark, eel and cephalopod molluscs. The way in which prey is hunted depends on the species of fish. Day-active fish are usually hunted by dolphins in groups, while fewer dolphins hunt nocturnal fish. An adult bottlenose dolphin can eat 8-15 kilos of fish a day. Dolphins help each other hunt. Whistling to each other, they circle around the school and prevent the fish from getting away. It is thought that dolphins also use sound to disorientate and stun fish. When there are enough fish, dolphins hunt during the day. When fish are scarce, dolphins hunt for octopus and bottom-dwelling fish. They do this at night, when octopuses and bottom-dwelling fish are active. Fishing at night usually involves fewer dolphins than fishing during the day.

Reproduction

The smallest mature female measured 228 cm. Pregnancy lasts 12 months and the rut lasts from 3-4 days to several weeks. During the rut, captive animals display special postures, bending of the body, jumping, 'sniffing', stroking each other's heads and fins, light nibbling and frequent squealing. In pairs, the male will chase away all rivals from the female. Short-term copulation is rapid and repeated several times. The sociability of pregnant females gradually diminishes and clumsiness and slowness of movement are observed as labour approaches.

The cub is born underwater with its tail pointing forward. The fetus takes between 20 minutes and 2 hours to be born. The end of the labour coincides with the strong agitation of the whole herd. The umbilical cord tears easily and the newborn, accompanied by the mother and one or two females, swims obliquely to the surface to take its first breath. Like the mother, the offspring are indifferent to the afterbirth.

After finding the mother's nipples, the calf will initially suckle them every 10-30 minutes while the female turns on her side. For the first few weeks, the calf will not swim far from its mother, but will later swim without restriction. In captivity, it first takes solid food at 3.5-6 months of age, but does not fully wean on milk until 18-23 months of age. Sexual maturity occurs at the age of 5-6 years.

Fishing

In many parts of the world, people kill large numbers of bottlenose dolphins every year for their meat, and some are captured for sale to dolphinariums.

Human interaction

In the wild, they are not aggressive towards humans, never attacking them, often showing friendly interest. They are rescued from sharks, accompany ships and help drowning people.