The bottlenose dolphin is regarded as one of the famous dolphin species. They are very intelligent, capable of solving problems and adaptable. The bottlenose dolphins are in two major varieties. That is the often smaller inshore form and the one which is larger, extremely robust and lives majorly offshore. The bottlenose dolphins are classified as Tursiops tuncatus. On the other hand, a distinct species was also found in the Indo-Pacific area has been recognized as the Tursiops aduncus. Hence the two common species of the bottlenose dolphins are the common Tursiops tuncatus and the Tursiops aduncus found in Indo-Pacific. The Tursiops tuncatus, Is relatively large dolphin which is up to four meters long, and light grey. The bottle dolphins live in tropical and temperate waters across the globe. Moreover, its coastal populations sometimes migrate into estuaries, bays and river mouths. Moreover, the offshore bottle dolphin populations mainly inhabit the pelagic waters alongside the continental shelf. The bottlenose dolphins are majorly found in the coastal waters of South Australia, Gulfs and the Port Adelaide River-Barker inlet estuary. Therefore, this paper explores the characteristics of the bottlenose dolphins.
The world’s estimated bottlenose dolphin population is about 600,000. The bottlenose dolphins have a large distribution. They are mainly found in continental shelf and coastal waters in temperate and tropical zones. The distribution of bottlenose dolphins is limited to 10o to 32o C. in the Pacific Ocean. The bottlenose dolphins begin to inhabit northern Japan, down to Australia. Also from Southern parts of California to Chile. In the eastern Tropical Pacific, the bottlenose dolphins are found along the offshore. Moreover, in the Atlantic Ocean, they can be traced from Nova Scotia to the region of Patagonia as well as Norway to South Africa, Cape Cod all the way to the Gulf of Mexico. They also inhabit the Black and Mediterranean Seas in lagoons, river mouths, and shallow bays. On the other hand, the Indo-Pacific bottlenose dolphins can be found at the Indian Ocean in Indonesia through to Australia, then South Africa to Red Sea and finally in the subtropical and tropical waters of West Pacific. Finally, the two offshore and coastal dolphins occupying the northwest Atlantic can be distinguished by body measurements, skull and blood characteristics (Hammond, Bearzi, Bjørge, Forney, Karkzmarski, Kasuya & Wilson 2014).
Bottlenose dolphins are dark or dark grey which may sometimes fade to pink white on their underside. A bottlenose dolphin often has a dark strip starting from its beaks base up to eye area. It also possess a noticeable snout and a protruding lower jaw against the upper jaw. It must be noted that bottlenose dolphin does possess a fusiform body which lacks several physical traits of a terrestrial mammal like hind limbs, external ears, and hair. Its fusiform body is to reduce water turbulence and enable it to cruise in water at accelerated speed. The bottlenose dolphin also has front flippers, flukes and dorsal fin for swimming. Its dorsal fin tail is curved and is set up almost at the center of its back. Its skull has a telescoped shape with elongated rostra, an elongated anterior and nostrils that are dorsally located (Hammond et, el). Hence, such features enable a bottlenose dolphin to breath with ease when swimming. Moreover, the bottlenose dolphin is both homoeothermic and endotherm. That is, it has insulation like blubber and vascular shunts to allow for thermoregulation (Wells & Eide 2000). The bottlenose dolphins’ thermo-neutral zone is 10o to 32o C hence the rising or decreasing of temperature reduces or increases metabolic rates (Berrow 2009).
Bottlenose dolphins are also 84 to 145 centimeters long and weigh about 14 to 20 kilograms at birth. The adult male bottlenose dolphin is often 245 to 385 centimeters long and weighs approximately 500kg. On the other hand, adult females are quite shorter in length. They are mainly 227 to 336 centimeters long, and approximately 250 kilograms in weight. The bottlenose dolphin has about 18 to 26 pairs of enormous teeth in every jaw. The European bottlenose dolphin is relatively larger than that in West Atlantic. Moreover, there are a significant color and size variations among the Tursiops truncatus across the globe.
Bottlenose dolphins have diets that vary from place to place. For instance, bottlenose dolphins do feed on invertebrates and fish found at the shoreline. On the contrary, when in deep waters, they tend to feed on pelagic and squid fish. Those found in the U.S. Atlantic coastlines tend to feed on croakers, silver perch and spot fish. The South African bottlenose dolphins eat African massebank, olive grunters, and Pandora. Moreover, bottlenose dolphins normally target preys that are between five and thirty centimeters long. They also eat approximately 4.6 to 17 kilograms daily based on the individual size of the dolphin and whether it is lactating. Interestingly, bottlenose dolphins tend to feed individually. However, sometimes, they take part in cooperative feeding with one another. Also, when hunting, bottlenose dolphins like to set-up their prey at the shore and strand-feed them. Sometimes they employ the echolocation calls to catch their prey. Interesting, when hunting, the bottlenose dolphins employ passive listening to locate the prey. After detecting or locating a prey, bottlenose dolphins will either go after it or instead alert others to come for the prey. Furthermore, their sharp teeth enable them to hold onto their preys while they use the tongue to thrust the game down their throats. It must be noted that dolphins do not chew but swallow their prey in whole. A bottlenose dolphin can also break the prey by striking it with its tail or shaking it vigorously in the air, a technique called “fish-whacking.” Finally, in the process of hunting, bottlenose dolphin is also famous for following fishermen’s boats to catch the discarded baits or fish (Würsig et. El, 2017).
Social Structure and Behavior
Bottlenose dolphins are known for exhibiting extremely acrobatic and outgoing traits, displaying curiosity to people and other mammal species. The bottlenose dolphin likes to travel in groups of 2 to 30 dolphins. However, during mating, they are likely to form groups of hundreds to thousands of dolphins. Moreover, bottlenose employ sound as a means of communicating with one another. Every dolphin has its signature whistle which is developed and retained from an early age. Therefore, kin can recognize each other’s whistle. The sounds also assist in maintaining group cohesion. Moreover, the signature whistle provides both the position and state of emotion of every bottlenose dolphin. Moreover, regarding their adaptation, the dolphins navigate with echolocation, use it to detect prey, topography and predators (Würsig et. El, 2017). They regularly surface to take breaths because they can only spend a maximum of seven minutes under the water. They also use vision to comprehend their environs. Like beings, the dolphin’s eyes have cones and rods. The cones offer proper acuity when the light is intensive. Finally, to adapt, they use vision at varying times of the day at varying depths (Würsig et. El, 2017).
Not all of the Tursiops truncatus make noteworthy migrations. Hover, some population of s of the bottlenose dolphins do make extended movements of about 200 kilometers at a specific time of the year mostly during breeding or when moving to hibernating sites. Sometimes they make regular between offshore and inshore areas or move linearly along the coast for close to 100 kilometers.
Bottlenose dolphins often engage in mating individually or in alliances. Male bottlenose dolphins sometimes form an alliance to search for females in estrous, isolated a female from her home just to mate with her. Sometimes, when in a group, the male bottlenose dolphin may flank the females to stop access by the other male dolphins. A male bottlenose dolphin will always wait for a female dolphin to be receptive or attempt to attract her into mating by bending the back, nuzzles then strokes the female or yelping its jaws (Wells & Eide 2000).
The female bottlenose dolphin normally attains the sexual maturity at about six to nine years of age. The male bottlenose dolphins tend to attain sexual maturity when they are eight and thirteen years old. Also, sexual maturity of bottlenose dolphins is often fulfilled several years before reproduction. For example, the male bottlenose dolphin will mature sexually at the age of ten years but cannot breed until it is approximately 20 years old. Moreover, breeding seasons for bottlenose dolphins differ from area of inhabitance. It is because the females tend to ovulate only at particular period or season, mostly warmer months, while the males are constantly sexually active. The pregnancy or gestation lasts approximately one year, and every pregnancy produces a single calf. The mother dolphin breastfeeds the calf up to the age of 18 to 20 months. Interestingly, the female bottlenose dolphins reproduce after every three to six years, with some becoming pregnant as soon as their calves are weaned (Wells & Eide 2000).
Bottlenose dolphins are always endangered by different causes which are either natural or human-made. Natural mortality is as a result of disease, predation and injury. On the other hand, since they live in shallow waters, bottlenose dolphins often encounter several human activities. Sometimes they get entangled in fishing hooks and nets, and environmental contamination. Therefore, naturally, the female bottlenose dolphins live for approximately 50 years while their male counterparts live for nearly 40 to 45 years (Wells & Eide 2000).
In conclusion, the bottlenose dolphin a very most famous specie of dolphin. They are classified as Tursiops tuncatus and Tursiops aduncus. The world’s estimated bottlenose dolphin population is about 600,000. They are mainly found in continental shelf and coastal waters in temperate and tropical zones. The bottlenose dolphin is dark grey with a fusiform body. Bottlenose dolphins have diets which always vary from one place to another. They tend to feed either individually or engage in cooperative feeding. They are also famous for following fishermen’s boats to catch the discarded baits or fish. During breeding, bottlenose dolphins often engage in mating individually or in alliances. The female bottlenose dolphin normally attains the sexual maturity at about five to ten years of age while the males do so at the age of eight and thirteen years. Moreover, the gestation period for a bottlenose dolphin is approximately one year where every pregnancy produces a single calf. Finally, the life-span for the female bottlenose dolphins is approximately 50 years while that of their male counterparts live for nearly 40 to 45 years.
Hammond, P. S., Bearzi, G., Bjørge, A., Forney, K. A., Karkzmarski, L., Kasuya, T., … & Wilson, B. (2014). Tursiops aduncus. The IUCN Red List of Threatened Species. Version, 2012.
Reynolds, III, J., R. Wells, S. Eide. 2000. The Bottlenosed Dolphin. Gainesville, FL: University Press of Florida.
Würsig, B., Thewissen, J. G. M., & Kovacs, K. M. (Eds.). (2017). Encyclopedia of marine mammals. Academic Press.
Berrow, S.D. 2009. Winter distribution of Bottle-nosed Dolphins (Tursiops truncatus (Montagu)) in the inner Shannon Estuary. Ir. Nat. J. 30: 35 – 39.