Bottlenosed dolphins are threatened by a variety of factors, both natural and of human origin. Natural mortality is due to injury, disease, and predation. Male bottlenosed dolphins typically live about 40 to 45 years and female dolphins can live over 50 years (the oldest female documented lived to be 53 years old). Because in many cases dolphins are found in shallow waters, they encounter many humans and human activities. Recreational fishing gear causes many deaths when dolphins become entangled in nets or swallow fishing hooks. Dolphins are sometimes preyed upon by sharks, although this is may be less of a problem now than in the past due to declining shark populations. One of the largest and most serious threats to bottlenosed dolphins is environmental contamination, caused mainly by the increase of human development along shorelines. Chemicals of human origin find their way into coastal ecosystems through runoff from agriculture, residential, and industrial sources.
Range lifespan
Status: captivity: 53 (high) years.
Average lifespan
Status: captivity: 45 years.
Average lifespan
Status: wild: 25.0 years.
Average lifespan
Status: captivity: 30.0 years.
Average lifespan
Status: wild: 25.0 years.
Average lifespan
Status: wild: 35.0 years.
Average lifespan
Status: wild: 25.0 years.
Bottlenosed dolphins are found everywhere except polar waters. Deep water bottlenosed dolphins come up to take breaths every 1 to 2 minutes, whereas inshore bottlenosed dolphins take breaths two times per minute. Bottlenosed dolphins have been known, however, to dive deep enough to go 4.5 minutes without taking a breath. Bottlenosed dolphins are found in bays, estuaries, sounds, open shorelines and large, estuarine rivers.
Average depth: 1 m.
Habitat Regions: temperate ; tropical ; saltwater or marine
Aquatic Biomes: pelagic ; coastal ; brackish water
Other Habitat Features: estuarine
Tursiops truncatus typically occupies waters with surface temperatures between 50 and 90 degrees Fahrenheit. Although some bottlenosed dolphins migrate seasonally (for example, populations along the Atlantic coast), they are typically found in tropical, subtropical, and warm temperate waters.
Biogeographic Regions: indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )
Other Geographic Terms: cosmopolitan
The diet of bottlenosed dolphins is broad and varies from one place to another. Inshore bottlenosed dolphins typically feed on fish and invertebrates found near the shoreline, while deep water bottlenosed dolphins typically feed on squid and pelagic fish. Bottlenosed dolphins found along the U.S. Atlantic coast typically feed on Atlantic croakers (Micropogonias undulatus), ‘spot’ fish (Leistomomus xanthurus), and silver perch (Bairdiella chrysoura), while dolphins in South Africa typically feed on African massbankers (Trachurus delagoae), olive grunters (Pomadasys olivaceus), and pandora (Pagellus bellotti). Bottlenosed dolphins typically choose prey between 5 and 30 cm in length. They eat between 4.5 and 16 kg per day, depending on the size of the individual and if it is lactating. Most of the time, bottlenosed dolphins feed individually. At times, however, dolphins participate in cooperative feeding with other dolphins, especially when feeding on a school of prey. They have also been known to trap their prey on the shore, stranding themselves in order to feed on stranded prey ("strand feeding"). And in some cases dolphins use echolocation calls to stun their prey. Some bottlenosed dolphins use passive listening rather than echolocation to locate prey. When prey is detected, these dolphins either rush in or alert others of the prey’s presence.
The sharp teeth of these dolphins allow them to grasp prey while the tongue maneuvers prey down the throat. Dolphins teeth are not used to chew and prey is typically swallowed whole. They may break up their prey by shaking it in the air and striking it with their tails, called fish-whacking. Bottlenosed dolphins in Australia may mount a sponge on their rostrum to protect their snouts as they forage on the bottom. They have also been known to follow the boats of fisherman and catch discarded prey or bait.
Animal Foods: fish; mollusks; aquatic crustaceans
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods, Molluscivore )
Bottlenosed dolphins feed on small fish and squid. They are hosts for a few species of parasites including the fluke Braunina cordiformis, tapeworms such as Monorygma delphini, roundworms (Anisakis marina), and thorny-headed worms (Corynosoma cetaceum). It has been said that healthy bottlenosed dolphin populations indicate a healthy marine ecosystem.
Ecosystem Impact: keystone species
Commensal/Parasitic Species:
Humans receive a considerable amount of economic gain from bottlenosed dolphins. They are often used in captivity to swim with humans and perform. Dolphins are used in tours in which participants are educated about the lives of dolphins and encouraged to preserve their livelihood and habitat. Bottlenosed dolphins have also been known to fish cooperatively with humans, letting Brazilian fishermen, for example, know when and where to drop their nets. Bottlenosed dolphins are even used for research by the U.S. Navy on echolocation and thermoregulation. These research dolphins have also helped navy divers to find submerged objects in the ocean. Research on bottlenosed dolphins has contributed substantially to our understanding of social communication and behavior and the nature of intelligence.
Positive Impacts: ecotourism ; research and education
There are no known adverse effects of Tursiops truncatus on humans.
Bottlenosed dolphins in the United States are protected under the Marine Mammal Protection Act of 1972. The goal of this Act is to allow marine species to obtain optimum sustainable population levels keeping in mind the carrying capacity of the habitat. Anyone who removes a marine animal (e.g., a dolphin) without proper procedure faces fines up to $20,000 or periods of incarceration up to one year. Bottlenosed dolphins are also protected under the Environment Protection and Biodiversity Conservation Bill of 1998 in Australia. This bill is applied to waters up to 200 miles from the shores of Australia. It involves environmental impact assessments, conservation of biodiversity and endangered species as well as management of protected areas. Bottlenosed dolphins are found in most waters and so are protected by many different laws in a large number of countries. Although there are laws that protect bottlenosed dolphins, humans need to become more aware of the way our daily lives affect the livelihood of dolphins. Much of the environmental contamination found in the habitats of bottlenose dolphins are caused by humans. Common pollutants found in the tissues of dolphin are polychlorinated biphenyls (PCB), used as dielectric fluids in coolants, lubricators and transformers, and pesticide DDTs (1,1-bis-(4-chlorophenyl)-2,2,2-trichloroethane). Eighty percent of the total amount of these toxins in a female dolphin may be transferred through breast milk to its calf, causing suppression of the immune system or in some cases death. It is one thing to make sure that we are not removing dolphins from their habitats but it is also important to make sure their habitats are not being destroyed by our negligence.
US Federal List: no special status
CITES: appendix i; no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
Bottlenosed dolphins use sound to communicate with other members of their groups. They use both audible sounds and high frequency echolocation. Each dolphin is believed to possess its own signature whistle and, once it is developed, it is retained for the duration of the dolphin’s life. Kin recognize one another by their whistles and these sounds help maintain group cohesion. Signature whistles develop in calves as young as one month, allowing them to maintain contact with their mother. Surprisingly, the signature whistle of a male calf tends to resemble its mother's more than that of a female calf. The signature whistle also gives the location and emotional state of each dolphin. Bottlenosed dolphins also navigate with echolocation, used to detect bottom topography, prey, and the presence of predators. It is even sometimes used to stun prey. Echolocation calls pass through the melon and intramandibular fat body, which contain acoustic lipids; these structures serve as acoustic lenses to focus sound. The intramandibular fat bodies focus sound to each ear, while the melon is used as a lens to focus outgoing sound.
Bottlenosed dolphins also use vision to perceive their surroundings. Like those of humans, their eyes contain rods and cones, but they are not used in the same way as humans. Cones, for example, are used to provide good acuity when light levels are high. These and other adaptations allow dolphins to use their vision at different times of the day and at different depths.
Communication Channels: visual ; tactile ; acoustic
Other Communication Modes: vibrations
Perception Channels: visual ; tactile ; acoustic ; echolocation ; vibrations ; chemical
Fossil remains of several Tursiops species have been found in Pliocene (2 to 5 million years old) and Pleistocene (less than 2 million years old) deposits. It has been suggested that Tursiops originated in the Mediterranean region. The teeth of bottlenosed dolphins are flattened at the tips, which caused them to be placed in the genus Tursio, but because Tursio is a synonym of Physeter, the genus name was changed to Tursiops. Tursio in Latin means dolphin, and the suffix -ops means appearance, hence the name, Tursiops. Trunco is the Latin term for truncated, which makes reference to the flattened teeth of bottlenosed dolphins. There are three synonyms of Tursiops truncatus: Tursiops gephyreus, Tursiops gillii and Tursiops nuuanu. Tursiops has recently been separated into two species: Tursiops truncatus and Tursiops aduncus.
Bottlenosed dolphins have a fusiform body that lacks many external characteristics of terrestrial mammals, including hair, external ears and hind limbs. A fusiform body reduces turbulence and allows bottlenosed dolphins to cruise underwater at high speeds. Dolphins have front flippers, a dorsal fin and flukes, which are used in swimming. The dorsal fin is tall, curved and set near the middle of the back. These dolphins are typically black to a light gray on their sides, and their bellies are white, sometimes with a slight pink hue. Bottlenosed dolphins are typically 84 to 140 cm at birth, and typically weigh between 14 and 20 kg. Adult males are usually between 244 and 381 cm long, and weigh about 500 kg. Adult females are typically between 228 and 366 cm, and weigh about 250 kg. This sexual dimorphism may be a result of females using energy to achieve sexual maturity at a earlier age than males, while males continue to grow.
As is true of all modern cetaceans, the skulls of bottlenosed dolphins are telescoped; that is, the rostra are elongated and tapered anteriorly and the nostrils are moved dorsally. This allows dolphins to breathe more easily during swimming. Bottlenosed dolphins are homeotherms and endotherms. They use insulation, in the form of blubber, a relatively small surface area due to their large body sizes, and vascular shunts that allow selective cooling of certain organs and tissues to help thermoregulate. Bottlenosed dolphins have a thermoneutral zone of 13 to 28 degrees Celsius. If the temperature of their environment drops below 13 degrees Celsius or rises above 28 degrees Celsius, their metabolic rate increases.
Range mass: 260 to 500 kg.
Average mass: 400 kg.
Range length: 228 to 381 cm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
The most common predators of bottlenosed dolphins are larger sharks, such as bull (Carcharhinus amboinensis), tiger (Galeocerdo cuvier), and dusky sharks (Carcharhinus altimus). These sharks prey on smaller dolphins, calves and female dolphins more than larger dolphins. It is not uncommon to observe dolphins with shark bites, demonstrating their survival of an attack. Blubber may provide some protection against predators. Many shark populations have decreased up to 80 percent since 1970, so some populations of dolphins may be experiencing lower predation by sharks. More recently, stingrays have been recognized as causing deaths in bottlenosed dolphin populations.
Known Predators:
Bottlenosed dolphins are polygamous. They engage in mating behavior in either of two ways, in alliances or individually. Males that form alliances look for females that are in estrous. When males find a female in estrous they separate her from her home range for a chance to mate with her. Sometimes they flank the female to prevent access by other males to insure that only they have the opportunity to mate with her. Waiting for a female to become receptive can take several weeks. Some males do not engage in alliances, instead remaining in their home ranges. When an estrous female enters the home range of such a male, he attempts to attract her to mate. During courtship, a male postures by arching his back. He strokes and nuzzles the female, and he may clap his jaws or yelp. Bottlenosed dolphin copulation typically occurs belly-to-belly with both animals facing the same direction, although an animal facing the opposite direction is not uncommon. Intromission lasts only around 10 seconds and involves vigorous pelvis thrusts.
Mating System: polygynandrous (promiscuous) ; cooperative breeder
Female dolphins typically reach sexual maturity between 5 and 10 years of age, while males reach sexual maturity between 8 and 13 years old. Sexual maturity is usually achieved years before reproduction; males that reach sexual maturity at age 10 don’t typically breed until they are at approximately 20 years old. Reproductive seasons vary from region to region. Typically, females ovulate at a particular time of year while males are active throughout the year (but with a peak of testosterone production when females ovulate). Gestation lasts about 12 months and each pregnancy produces one calf. Females nurse their young from nipples on each side of their genital slit until the calf is between 18 and 20 months. Bottlenosed dolphins reproduce every 3 to 6 years, with females usually becoming pregnant soon after their calf is weaned. Calves can be born at any time of the year but with a peak in birthing during warmer months. Females can reproduce well into their late forties.
Breeding interval: Female bottlenosed dolphins breed once every 3 to 6 years.
Breeding season: Breeding may occur throughout the year but is often concentrated in the warmer months.
Average number of offspring: 1.
Average gestation period: 12 months.
Range weaning age: 18 to 20 months.
Average time to independence: 5 years.
Range age at sexual or reproductive maturity (female): 5 to 10 years.
Range age at sexual or reproductive maturity (male): 8 to 13 years.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Average birth mass: 19350 g.
Average gestation period: 365 days.
Average number of offspring: 1.
Females provide the bulk of parental investment, investing especially heavily during lactation. Lactation in bottlenosed dolphins typically lasts 18 to 20 months. Lactating females require 88 to 153 cal/kg as opposed to non-lactating females that typically require 34 to 67 cal/kg. Bottlenosed dolphins participate in allomaternal care, that is, all of the females within a group help care for each others' offspring. When a bottlenosed dolphin calf is born, it learns to ride the pressure waves alongside its mother during its first few days. The mother assists the calf to keep it alongside her body. Females also protect calves from predators.
Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); post-independence association with parents
Red and Mediterranean Sea.
Unknown; probably breeding.
Thesehighly intelligent animalsare grey in colour, typically 2 – 4 metres long and weigh between 300 – 500 kgs. These dolphins have short, well developed snout that resembles an old fashioned gin bottle – the source of its common name. This snout houses 18 – 28 conical teeth on each side of the jaw allow the dolphin to grasp its prey while its tongue manoeuvres the prey item down its throat.
The diet of bottlenose dolphins is broad and varies according to region. However, their diet primarily consists of fish, crustaceans and squid. Dolphins are team players and live in social groups called pods. Once a shoal of fish is found, typically byecholocation(a type of sonar), dolphins work together to herd the fish together and maximise the number of prey from the hunt.
Another feeding strategy is ‘strand feeding’where dolphins chase their prey to shore and knowingly strand themselves to feed. Bottlenose dolphins are the poster children ofinterspecies cooperation. Fishermen and dolphins work together in the town of Laguna, Brazil. A pod of bottlenose dolphins would drive fish toward fishermen standing in shallow waters. One dolphin rolls over and the fishermen throw out their nets. The dolphins feed on the escaping fish. These dolphins were not trained to do this and this collaboration began before 1847. This behaviour has been noted in other places around the globe.
Coastal and island-centred populations are especially vulnerable to hunting, incidental catch, and habitat degradation (SourceIUCN). Worldwide reports indicate that dolphins are caught for bait, human consumption, or to remove competition in the fishing industry. Drive fisheries have been reported for the Faroe Islands and Japan. Theaverage catch rate in Japan was 594 dolphins per annum from 1995–2004.
Dolphins have captured the minds and hearts of people for centuries due to their altruistic behaviour. How often do we hear tales of dolphins saving surfers fromsharks? It’s practically cliché at this point. They are also known to help other animals who find themselves introuble.Militarieshave trained these dolphins for wartime tasks such as mine detection and locating enemy divers. And researchers are still developing new tests in attempts to determine the intelligence of the dolphins.
All in all, it seems that we are still fascinated with these dolphins. And based on interactions between our two species (both historic and current), the feeling is mutual.
For more information on MammalMAP, visit the MammalMAPvirtual museumorblog.
The common bottlenose dolphin or Atlantic bottlenose dolphin (Tursiops truncatus) is a wide-ranging marine mammal of the family Delphinidae. The common bottlenose dolphin is a very familiar dolphin due to the wide exposure it gets in captivity in marine parks and dolphinariums, and in movies and television programs.[5] It is the largest species of the beaked dolphins.[6] It inhabits temperate and tropical oceans throughout the world,[7] and is absent only from polar waters.[5][6][8][9][10] While formerly known simply as the bottlenose dolphin, this term is now applied to the genus Tursiops as a whole.[1][11][12] As considerable genetic variation has been described within this species, even between neighboring populations, many experts think additional species may be recognized.[13][11]
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.[9][10][13][14][15][16] The two species are thought to have split during the mid-Pleistocene, about 1 million years ago.[17]
Currently, three common bottlenose dolphin subspecies are recognized:[4]
Bottlenose dolphins along the southern California and Baja California coasts were previously recognized as the Pacific bottlenose dolphin, T. t. gillii.[18] The name has since been reclassified as a junior synonym of Tursiops truncatus.[19]
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.[17]
Common bottlenose dolphins are grey, and between 2 and 4 m (6.6 and 13.1 ft) long, and weigh between 150 and 650 kg (330 and 1,430 lb).[14] Males are generally larger and heavier than females. In most parts of the world, adult length is between 2.5 and 3.5 m (8.2 and 11.5 ft); weight ranges between 200 and 500 kg (440 and 1,100 lb).[6][11] Dolphins have a short and well-defined snout that looks like an old-fashioned gin bottle, which is the source for their common name.[20]
Like all whales and dolphins, though, the snout is not a true nose; the nose instead evolved into the blowhole on the top of their heads. Their necks are more flexible than other dolphins' due to five of their seven vertebrae not being fused together like in other dolphins.[21]
The common bottlenose dolphin has a larger brain than humans.[22] Many investigations of bottlenose intelligence include tests of mimicry, use of artificial language, object categorization, and self-recognition.[23][24][25][26][27][28] This intelligence has driven considerable interaction with humans. The common bottlenose dolphin is popular in aquarium shows and television programs such as Flipper.[29] 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.[30][31] In some areas, they cooperate with local fishermen by driving fish toward the fishermen and eating the fish that escape the fishermen's nets.[32]
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.[11] The types of groups include: nursery groups, juvenile groups, and groups of adult males.[6]
Its diet consists mainly of eels, squid, shrimp and a wide variety of fishes.[1][8] 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.
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.[6]
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.[33]
Research indicates that the type and range of fish in a dolphin's diet can have a significant impact on its health and metabolism.[34]
Dolphins also use sound for communication, including squeaks emitted from the blowhole, whistles emitted from nasal sacs below the blowhole, and sounds emitted through body language, such as leaping from the water and slapping their tails on the water. The dolphins address each other individually through matched whistling, where individuals respond to whistles of other dolphins by using the same whistle.[35]
Their heads contain an oily substance that both acts as an acoustic lens and protects the brain case. They emit clicking sounds and listen for the return echoes to determine the location and shape of nearby items, including potential prey.[36]
Mating behavior of bottlenose dolphin is polygamous. Although they can breed throughout the year, it mostly occurs in spring.[6] Males form alliances to seek an estrous female. For a chance to mate with the female, males separate the female from her home range.[6] Females bear a calf every three to six years.[6][37] After a year-long gestation period, females bear a single calf.[6] 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).[11] They can live as long as 40–50 years.[38] The calf's suckling lasts between 18 and 20 months[6] and they are weaned between three and eight years of age.[39] Sexual maturity varies by population, and ranges from 5–14 years of age;[38] sexual maturity occurs between 8 and 13 years for males and 5 to 10 years for females.[6]
The average life expectancy of common bottlenose dolphins is about 17 years old,[40][41][42][43] but in captivity they have been known to live to up to 51 years old.[44]
The common bottlenose dolphin can be found in temperate, subtropical, and tropical oceans around the world.[45] The global population has been estimated at 600,000.[46] Some bottlenose populations live closer to the shore (inshore populations) and others live further out to sea (offshore populations).[47] Generally, offshore populations are larger, darker, and have proportionally shorter fins and beaks. Offshore populations can migrate up to 4,200 km (2,600 mi) in a season, but inshore populations tend to move less. However, some inshore populations make long migrations in response to El Niño events.[11] The species has occurred as far as 50° north in eastern Pacific waters, possibly as a result of warm water events.[48] The coastal dolphins appear to adapt to warm, shallow waters. It has a smaller body and larger flippers, for maneuverability and heat dispersal. They can be found in harbors, bays, lagoons and estuaries. Offshore dolphins, however, are adapted to cooler, deeper waters. Certain qualities in their blood suggest they are more suited to deep diving. Their considerably larger body protects them against predators and helps them retain heat.[49]
Some interactions with humans are harmful to the dolphins. Dolphin hunting industry exists in multiple countries including Japan, where common bottlenose dolphins are hunted for food annually in the town of Taiji,[50] and the Faroe Islands. Also, dolphins are sometimes killed inadvertently as a bycatch of tuna fishing.[51][52]
Tião was a well-known solitary male bottlenose dolphin that was first spotted in the town of São Sebastião in Brazil around 1994 and frequently allowed humans to interact with him. The dolphin later became infamous for killing a swimmer and injuring many others, which earned it the nickname of killer dolphin.
Fungie is another solitary male bottlenose, living in close contact with humans in Dingle Harbour, Ireland, since 1983. He has become a symbol of the town, although some doubt exists over whether he is a single dolphin.[53]
The North Sea, Baltic, Mediterranean and Black Sea populations of the common bottlenose dolphin are listed in Appendix II[54] to the Convention on the Conservation of Migratory Species of Wild Animals (CMS) of the Bonn Convention, since they have an unfavorable conservation status or would benefit significantly from international cooperation organized by tailored agreements.[55]
The species is included in Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning international trade (including in parts/derivatives) is regulated.[3]
Estimated population of a few specific areas are including:[9]
The species is covered by the Agreement on Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS), the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS), the Memorandum of Understanding for the Conservation of Cetaceans and Their Habitats in the Pacific Islands Region,[56] and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia.[57]
Common bottlenose dolphins are the most common apex predators found in coastal and estuarine ecosystems along the southern coast of the US,[58] thus serve as an important indicator species of bioaccumulation and health of the ecosystem.
It is believed that some diseases commonly found in dolphins are related to human behaviors, such as water pollution. Water pollution is linked to point and non-point source pollution. Point source pollution comes from a single source such as an oil spill[59] and/or chemical discharge from a specific facility. The environmental impact of the Deepwater Horizon oil spill caused a direct impact and still serves as a long-term impact of future populations. Common bottlenose dolphins use these important habitats for calving, foraging, and feeding. Environmental impacts or changes from chemicals or marine pollution can alter and disrupt endocrine systems, affecting future populations. For example, oil spills have been related to lung and reproductive diseases in female dolphins. A recent study[60] suggested signs of lung disease and impaired stress in 32 dolphins that were captured and assessed in Barataria Bay, Louisiana, US. Out of these 32 dolphins, 10 were found pregnant and, upon a 47-month check up, only 20% produced feasible calves, compared to a previous success rate of 83%, in the same area. It is believed that a recent oil spill in this area is partially to blame for these severely low numbers.
Dense human development along the eastern coast of Florida and intense agricultural activity have resulted in increased freshwater inputs, changes in drainage patterns, and altered water quality (i.e. chemical contamination, high nutrient input, decreased salinity, decreased sea grass habitat, and eutrophication.[61] High nutrient input from agriculture chemicals and fertilizers causes eutrophication[62] and hypoxia, causing a severe reduction in water quality. Excess of phosphorus and nitrogen from these non-point sources deplete the natural cycle of oxygen by overconsumption of algae. Harmful algal blooms are responsible for dead zones and unusual mortality events of common bottlenose dolphins consuming these toxic fish from the brevetoxin produced by the dinoflagellate Karenia brevis.[63] Brevetoxins are neurotoxins that can cause acute respiratory and neurological symptoms, including death, in marine mammals, sea turtles, birds, and fishes.[64]
The common bottlenose dolphin or Atlantic bottlenose dolphin (Tursiops truncatus) is a wide-ranging marine mammal of the family Delphinidae. The common bottlenose dolphin is a very familiar dolphin due to the wide exposure it gets in captivity in marine parks and dolphinariums, and in movies and television programs. It is the largest species of the beaked dolphins. It inhabits temperate and tropical oceans throughout the world, and is absent only from polar waters. While formerly known simply as the bottlenose dolphin, this term is now applied to the genus Tursiops as a whole. As considerable genetic variation has been described within this species, even between neighboring populations, many experts think additional species may be recognized.
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