BOTTLENOSE DOLPHIN: CHARACTERISTICS, SUBSPECIES, HABITAT, FEEDING - BIOLOGY - 2025

The bottlenose dolphin (Tursiops truncatus) is a placental mammal that is part of the Delphinidae family. It has a streamlined body, the upper part of which is gunmetal gray, with a darker stripe along the spine. On the sides it has a light gray tone, which ends in a white belly.

It inhabits the tropical and temperate oceans around the world, although it is absent in polar waters. The tonina, as this species is also known, lives in a great diversity of ecosystems. Thus, they are found in both coastal and pelagic waters

Bottlenose dolphin. Source: NASA

Its snout is short, shaped like an inverted bottle. The nostrils are modified, since they are displaced towards the back of the skull. This morphological adaptation allows this cetacean to breathe without taking its head out of the water, just as it can while swimming.

characteristics

The bottlenose dolphin has a spindle-shaped body, which helps reduce turbulence. This makes it easy to navigate underwater at high speed. This species has a tall, curved dorsal fin located near the middle of the back. His height is around 23 centimeters.

As for the pectoral fin, it is broad at the base, with a rounded tip. This is between 30 and 50 centimeters long. Relative to the tail fin, it is approximately 60 centimeters wide.

Coloration

The upper part is leaden gray, with a distinctive slightly darker stripe, running from head to tail. The sides are light gray and the belly is white, and may have a slight pinkish hue.

Size

The adult male weighs around 500 kilograms and measures 244 to 381 centimeters. For its part, the female has a body mass of 250 kilograms and the total length of her body is between 228 and 366 centimeters.

Head

As in all modern cetaceans, the bottlenose dolphin skull is telescopic. In this, the maxilla and premaxilla are elongated, resulting in the displacement of the nostrils towards the rear dorsal part of the skull.

These adaptations allow the dolphin to breathe without having to lift its head out of the water or stop walking.

This species has a short snout, which is about 8 centimeters long. In this there are between 18 and 26 pairs of sharp and conical teeth, with a diameter of approximately 1 centimeter.

Regulation of internal temperature

The Tursiops truncatus is a homeothermic animal. This species has a thermoneutral zone of 13 to 28 ° C. If the environmental temperature is lower or higher than these ranges, the organism has some adaptations that allow it to keep its internal temperature stable.

One of the thermal insulation mechanisms is the thick layer of fat, which is deposited under the skin. In the hot season, it loses volume, while during the winter it becomes thicker.

On the other hand, in the lobes of the caudal fin and in the dorsal fin there is a network of superficial capillaries, known as the rete mirabile. This works as a countercurrent heat exchange structure.

Echolocation

The bottlenose dolphin uses a technique known as echolocation, which allows it to locate its prey or objects. He also uses it to detect the topography of the seabed and even to stun other animals.

The sounds emitted by the dolphin collide with objects and return to the animal, where it is captured and interpreted with the brain.

The Tursiops truncatus, have a very sensitive wideband hearing, extending up to 150 kHz. Thus, this cetacean could have a maximum echolocation range of 100 to 600 meters in oceanic waters.

As for the brain, it is relatively large. This may be related to the need to rapidly process echoes in water, where sound travels almost five times faster than in air.

Vocalizations

The bottlenose dolphin produces a variety of vocalizations, including clicking, hissing, and blasting sounds. Experts note that this animal can spontaneously mimic the sound of the whistle used in research tests of its various abilities.

Likewise, the temporal and spectral characteristics of the whistles of the Tursiops truncatus have a very marked geographical variation. Furthermore, various experimental studies indicate that the clicks used for echolocation also have some vocal flexibility.

Behavior

The bottlenose dolphin is a very sociable animal. It generally lives in groups of various sizes, and there may be up to 100 dolphins. These groups can be brood, formed by mother females and their offspring, juveniles, made up of young people of both sexes, and adult males.

The dominance hierarchy is based on size, age, and sex. Due to these patterns, adult males dominate the rest of the group. In the event that it is absent, the larger adult female takes over.

The Tursiops truncatus has a very particular behavior. When a member of the group is attacked by a predator, the rest of the group comes to their aid. Thus, they take turns to hit the intruder with their snout, until they get it to move away.

Also, the bottlenose dolphin helps in the recovery of other dolphins that are injured. It can protect you or keep the injured cetacean on the surface of the water.

Taxonomy and subspecies

-Animal Kingdom.

-Subreino: Bilateria

-Filum: Cordate.

-Subfilum: Vertebrate.

-Superclass: Tetrapoda

-Class: Mammal.

-Subclass: Theria.

-Infraclass: Eutheria.

-Order: Cetacea.

-Suborder: Odontoceti.

-Family: Delphinidae.

-Gender: Tursiops.

-Species: Tursiops truncatus.

Subspecies:

- Tursiops truncatus gillii.

Habitat and distribution

Distribution

The bottlenose dolphin is distributed worldwide, in temperate, tropical, subtropical and oceanic coastal waters, except for the polar ones. Thus, it can inhabit the Mediterranean Sea, the Black Sea and the southwest of the Indian Ocean. It is rare to find it in the Baltic Sea, but it occurs regularly in the Red and Arabian Sea.

In relation to the Pacific Ocean, this species is found from central California and northern Japan to Chile and Australia. In the Atlantic Ocean, they extend from Georges Bank and the British Isles to northern Namibia and Tierra del Fuego (Argentina).

In the United States, Tursiops truncatus lives along the west coast of California, Washington, and Oregon, and on the Hawaiian Islands. It is also on the coast and offshore, spanning from Florida to New York, in the Caribbean Sea and in the Gulf of Mexico.

Habitat

The bottlenose dolphin is commonly found in a great diversity of habitats, from coastal to pelagic waters, in the open ocean. Thus, they frequent estuaries, lagoons, bays, gulfs and other shallow areas. On the coasts of North America they live in areas with surface temperatures between 10 and 32 ° C.

As for those that inhabit the semi-enclosed basin of the Black Sea, they do so on the shelf, although they can sometimes be far from the coastal area.

The Tursiops truncatus establishes associations, where its group composition, per day or per hour, can vary. This allows the animal to explore a wide range of habitats, both coastal and oceanic.

Population genetic studies carried out in the Gulf of California have differentiated two ecotypes of the bottlenose dolphin, one pelagic and the other coastal. Each one presents differences in distribution and group association, as well as in morphology and feeding.

The coastal ecotype occurs in waters with a depth of up to 20 meters, where visibility is low and the bottom is sandy. In this area, the bottlenose dolphin has limited movement patterns, while in the oceanic ecotype the movements are less restricted.

State of conservation

Tursiops truncatus populations have declined, motivated, among other factors, to the degradation of their natural habitat. Because of this, the IUCN has categorized this species as least concern of going extinct.

- Threats

Interactions with fishing elements

One threat to bottlenose dolphins is that they get caught in fishing gear. In this way, it becomes entangled in purse seines, traps, gillnets, longlines and in trawl nets.

In addition, the animal can find the rod and reel tackle in the water, used by recreational game fishermen. Thus, the dolphin is injured or killed, due to entanglement or ingestion of the equipment.

Habitat degradation

The species that inhabit the coasts are harmed by the pollution of the waters due to the use of polluting agents, such as chemical waste, and by oil spills.

An example of this is the effects of the Deepwater Horizon oil spill, which occurred in 2010. Cetaceans in that area had serious immune system problems, as well as their reproductive success.

Likewise, the development of the coastal zone and the increase in boat traffic seriously affect the communities of this cetacean.

Biotoxins

In recent years there have been several deaths, related to the red tide. This situation has occurred in various parts of the Gulf of Mexico and along the coasts of Florida.

The bottlenose dolphin is exposed to algae biotoxin through the air or when ingesting contaminated prey, causing serious health problems.

- Actions

The Tursiops truncatus is included in the appendix II of CITES. However, the group of these dolphins that live in the Black Sea has a special protection, since it does not have a permit for export, as long as it is for commercial purposes.

In the wide range of its distribution, the governments of the countries ensure the protection of this species. Thus, in the United States it is protected by the Marine Mammal Protection Act. The main objective of this legal regulation is to ensure an optimal and sustainable population level of the bottlenose dolphin.

Likewise, in Australia, the Environmental Protection and Biodiversity Conservation Act establishes environmental impact assessments, strategies for the management of protected areas and for the conservation of biodiversity in danger of extinction.

Reproduction

The female is usually sexually mature when she is between 5 and 10 years old, while the male can reproduce at the age of 8 and 13 years. However, the male does not usually mate until he is around 20 years old.

The reproductive seasons have variations according to the region. Females tend to ovulate in a specific period. Conversely, males are active throughout the year, with a peak in testosterone at the time that females are in estrus.

The Tursiops truncatus is a polygamous animal. In relation to courtship, males fight each other for females in heat, which leads to the establishment of a hierarchy based on size. To attract the female, the male poses in front of her with his back arched, rubbing and stroking her with his snout.

Also, the pre-copulatory behavior could turn violent, involving strong blows with the head between the couple. As for copulation, it occurs when the female turns on her side and presents her belly to the male. Once ventrally attached, the male inserts his penis into the female's cloaca.

In the following video you can see the mating of dolphins of this species:

Breeding

After 12 months of gestation the calf is born. This weighs between 9 and 11 kilograms and measures about 126 centimeters. The mother breastfeeds her for 12 to 18 months, although by the time she is 6 months old she can already eat solid foods.

Regarding the upbringing of the young, all the females of the group participate, however, there is a strong bond between the young and its mother. In this video you can see a birth of this species:

Feeding

The bottlenose dolphin has a very varied diet, based on fish, crustaceans and cephalopods. However, due to its extensive distribution, eating habits vary according to the region where it is found.

Thus, those that live in the high seas eat various species of fish and pelagic squid, while the coastal ones consume invertebrates and benthic fish.

On the other hand, bottlenose dolphins that are distributed along the Atlantic coast of the United States feed on Atlantic croaker (Micropogonias undulatus), silver perch (Bairdiella chrysoura) and spotted fish (Leistomomus xanthurus).

As for those who live in South Africa, they consume banks of African masses (Trachurus delagoae), pandora (Pagellus bellotti) and olive snoring (Pomadasys olivaceus).

They also tend to hunt Atlantic mackerel (Scomber scombrus), blue whiting (Micromesistius poutassou), hake (Merluccius merluccius), Atlantic croaker (Micropogonias undulatus), horse mackerel (Scomberomorus cavalla), squid of the genus Loligo, and Atlantic squid (Loligo).

Eating methods

The Tursiops truncatus can feed individually, but it also forms food groups. In these, they work in an organized and cooperative manner to hunt schools of fish. It can also locate and capture its prey through echolocation.

To hunt, the bottlenose dolphin approaches the fish, catches it and holds it tightly with its teeth. You can then shake it hard or hit your body against the water or with your tail. Frequently, this species persecutes fishing boats, to consume those animals that were discarded or to take captive fish that are found in fishing nets.

References

1. Jenkins, J. (2009). Tursiops truncatus. Animal Diversity. Recovered from animaldiversity.org.
2. NOAA Fisheries (2019). Common Bottlenose Dolphin. Recovered from fisheries.noaa.gov
3. Vincent M. Janik, Peter JB Slater (1997). Vocal Learning in Mammals. Recovered from sciencedirect.com.
4. H. Ridgway, WWL Au (2009). Hearing and Echolocation in Dolphins. Recovered from sciencedirect.com.
5. Wikipedia (2019). Common bottlenose dolphin. Recovered from en.wikipedia.org.
6. ITIS (2019). Tursiops truncates. Recovered from itis.gov.
7. MarineBio (2019), Common Bottlenose Dolphins, Tursiops truncates. Recovered from marinebio.org.
8. FAO (2019). Tursiops truncatus (Montagu, 1821). Recovered from fao.org.