Aerial view of a pod of Indo-Pacific bottlenose dolphins (Tursiops aduncus) with calves at Gordon's Bay, Sydney.
The Indo-Pacific bottlenose dolphin (Tursiops aduncus) is a species of bottlenose dolphin. This dolphin grows to 2.6m (8.5ft) long, and weighs up to 230kg (510lb).[4] It lives in the waters around India, northern Australia, South China, the Red Sea, and the eastern coast of Africa.[4] Its back is dark grey and its belly is lighter grey or nearly white with grey spots.[4]
The Indo-Pacific bottlenose dolphin is generally smaller than the common bottlenose dolphin, has a proportionately longer rostrum, and has spots on its belly and lower sides.[5][6] It also has more teeth than the common bottlenose dolphin— 23 to 29 teeth on each side of each jaw compared to 21 to 24 for the common bottlenose dolphin.[6]
Much of the old scientific data in the field combine data about the Indo-Pacific bottlenose dolphin and the common bottlenose dolphin into a single group, making it effectively useless in determining the structural differences between the two species. The IUCN lists the Indo-Pacific bottlenose dolphin as "near threatened" in their Red List of endangered species.[2]
Taxonomy
Until 1998, all bottlenose dolphins were considered members of the single species T. truncatus. But in that year, the Indo-Pacific bottlenose dolphin was recognized as a separate species.[5][7] Both species are thought to have split during the mid-Pleistocene, about 1 million years ago.[8]
Some evidence shows the Indo-Pacific bottlenose dolphin may actually be more closely related to certain dolphin species in the genera Stenella and Delphinus, especially the Atlantic spotted dolphin (S. frontalis), than it is to the common bottlenose dolphin.[5][9] 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.[8]
The Burrunan dolphin (T. (aduncus) australis) has been alternately considered its own species, a subspecies of T. truncatus, or a subspecies of T. aduncus. Following the results of a 2020 study, the American Society of Mammalogists presently classifies it as a subspecies of T. aduncus.[8][10] The same study delineated 3 distinct lineages within T. aduncus which could each be their own subspecies: an Indian Ocean lineage, an Australasian lineage, and the Burrunan dolphin.[8] The Society for Marine Mammalogy does not recognize the Burrunan dolphin as a distinct species or subspecies, citing the need for further research.[11]
Description
Indo-Pacific bottlenose dolphins are very similar to common bottlenose dolphins in appearance. Common bottlenose dolphins have a reasonably strong body, moderate-length beak, and tall, curved dorsal fins; whereas Indo-Pacific bottlenose dolphins have a more slender body build and their beak is longer and more slender.[12] The Indo-Pacific population also tends to have a somewhat lighter blue colour and the cape is generally more distinct, with a light spinal blaze extending to below the dorsal fin. However, although not always present, the most obvious distinction can be made with the presence of black spots or flecks on the bellies of adults of Indo-Pacific bottlenose dolphins, which are very rare in common bottlenose dolphins.[12] Their teeth can number between 23 and 29 in each upper and lower jaw, and are more slender than those of common bottlenose dolphins.[12] Size of Indo-Pacific bottlenose dolphins can vary based on geographic location; however, its average length is 2.6m (8.5ft) long, and it weighs up to 230kg (510lb).[4] The length at birth is between 0.84 and 1.5m (2.8 and 4.9ft).[4]
The local population centering Mikura-jima is claimed to be a distinct form or species.[13]
Diet
Indo-Pacific bottlenose dolphins feed on a wide variety of fish and cephalopods (particularly squid).[14]
In one study,[14] researchers looked at the feeding ecology of Indo-Pacific bottlenose dolphins by analyzing the stomach contents of ones that got caught in the gillnet fisheries off Zanzibar, Tanzania. The prey items found in the stomach contents included 50 species of bony fish and three species of squid. From their results, the researchers concluded the most important prey group was fish, which accounted for 87% of the total number of prey items consumed and occurred in 24 of 26 stomachs examined. Cephalopods comprised the other 13% of prey items and were found in 13 of the 26 stomachs.[14] The remains of some crustaceans were also found; they hypothesize, however, they were consumed secondarily, since a number were found intact in the fish prey stomachs and therefore were not included in the diet analysis.[14]
Indo-Pacific bottlenose dolphins live in groups that can number in the hundreds, but groups of five to 15 dolphins are most common.[6] In some parts of their range, they associate with the common bottlenose dolphin[6] and other dolphin species, such as the humpback dolphin.[6]
The peak mating and calving seasons are in the spring and summer, although mating and calving occur throughout the year in some regions. The gestation period is about 12 months. Calves are between 0.84 and 1.5m (2.8 and 4.9ft) long, and weigh between 9 and 21kg (20 and 46lb). The calves are weaned between 1.5 and 2.0 years, but can remain with their mothers for up to 5 years. The interbirth interval for females is typically 4.5 to 6 years.[4]
In some parts of its range, this dolphin is subject to predation by sharks;[6] its lifespan is more than 40 years.[4]
Indo-Pacific bottlenose dolphins located in Shark Bay, Australia, have been observed using sponges as tools in a practice called "sponging". A dolphin breaks a marine sponge off the sea floor and wears it over its rostrum, apparently to probe substrates for fish, possibly as a tool.[15][16]
The first report and footage of spontaneous ejaculation in an aquatic mammal was recorded in a wild Indo-Pacific bottlenose dolphin near Mikura Island, Japan, in 2012.[17]
Indo-Pacific bottlenose dolphins have been observed to swim near and rub themselves against specific types of corals and sponges. A team of scientists followed up on this behavior and discovered metabolites with antibacterial, antioxidative, and hormonal activities in the corals and sponges, suggesting that they might be used by the dolphins to treat skin infections.[18]
Status and threats
The species is not considered to be endangered; its near-shore distribution, though, makes it vulnerable to environmental degradation, direct exploitation, and problems associated with local fisheries.[19]
The major predators of this species are typically sharks, and may include humans, killer whales (Orcinus orca), and stingrays. In the early 1980s, many were deliberately killed in a Taiwanese driftnet fishery in the Arafura Sea, off northwestern Australia.[20] Large-mesh nets set to protect bathers from sharks in South Africa and Australia have also resulted in a substantial number of deaths.[21] Gillnets are also having an impact, and are a problem throughout most of the species' range.
Captivity
These small cetaceans are commonly found in captivity,[14] causing conservation concerns, including the effects of removing the animals from their wild populations, survival of cetaceans during capture and transport and while in captivity, and the risks to wild populations and ecosystems of accidentally introducing alien species and spreading epizootic diseases, especially when animals have been transported over long distances and are held in sea pens.[22]
Bottlenose dolphins are the most common captive cetaceans on a global scale.[22] Prior to 1980, more than 1,500 bottlenose dolphins were collected from the United States, Mexico, and the Bahamas, and more than 550 common and 60 Indo-Pacific bottlenose dolphins were brought into captivity in Japan.[22] By the late 1980s, the United States stopped collecting bottlenose dolphins and the number of captive-born animals in North American aquaria has increased from only 6% in 1976 to about 44% in 1996.
In the South Korea, in the 2010s, environmental groups and animal protection groups led a campaign (2013년 대한민국 남방큰돌고래 방사) to release southern bottlenose dolphins illegally captured by fishermen and trapped in Jeju Pacific Land[23] and Seoul Zoo.[24]
In 2019, Canada banned the trade, possession, capture, and breeding of whales, dolphins, and porpoises for entertainment through passing Bill-203, also known as the Ending the Captivity of Whales and Dolphins Act. [25]
Japan
In a study on three populations of Indo-Pacific bottlenose dolphins in Japan,[26] the characteristics of acoustic signals are believed to be affected by the acoustic environments among habitats, and geographical variation in animal acoustic signals can result from differences in acoustic environments; therefore, the characteristics of the ambient noise in the dolphins' habitats and the whistles produced were compared. Ambient noise was recorded using a hydrophone located 10 m below the surface and whistles were recorded by using an underwater video system.
The results showed dolphins produced whistles at varying frequencies with greater modulations when in habitats with less ambient noise, whereas habitats with greater ambient noise seem to cause dolphins to produce whistles of lower frequencies and fewer frequency modulations. Examination of the results suggest communication signals are adaptive and are selected to avoid the masking of signals and the decrease of higher-frequency signals. They concluded ambient noise has the potential to drive the variation in whistles of Indo-Pacific bottlenose dolphin populations.
Jervis Bay, Australia
Small, motorized vessels have increased as a source of anthropogenic noise due to the rise in popularity of wildlife viewing such as whale watching. Another study[27] showed powerboat approaches within 100 m altered the dolphin surface behaviour from traveling to milling, and changed their direction to travel away from the powerboat. When the powerboat left the area and its noise ceased, the dolphins returned to their preceding behaviour in the original direction.
Another study[28] in Shark Bay, Western Australia, on dolphin behavioural responses showed significant changes in the behaviour of targeted dolphins were found when compared with their behaviour before and after approaches by small watercraft. Dolphins in the low-traffic site showed a stronger and longer-lasting response than dolphins in the high-traffic site. These results are believed to show habituation of the dolphins to the vessels in a region of long-term vessel traffic. However, when compared to other studies in the same area, moderated responses, rather, were suggested to be because those individuals sensitive to vessel disturbance left the region before their study began.
Although these studies do show statistical significance for the effects of whale-watching boats on behavior, what these results mean for long-term population viability is not known. The Shark Bay population has been forecast to be relatively stable with little variation in mortality over time (Manlik et al. 2016).[29]
Conservation
The Indo-Pacific bottlenose dolphin populations of the Arafura and the Timor Sea are listed on Appendix II[30] of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). They are listed on Appendix II[30] as they have an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements.[31]
A dolphin is an aquatic mammal in the clade Odontoceti. Dolphins belong to the families Delphinidae, Platanistidae, Iniidae, Pontoporiidae, and possibly extinct Lipotidae. There are 40 extant species named as dolphins.
The bottlenose dolphin is a toothed whale in the genus Tursiops. They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus contains three species: the common bottlenose dolphin, the Indo-Pacific bottlenose dolphin, and Tamanend's bottlenose dolphin. Others, like the Burrunan dolphin, 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 the truncated teeth.
Oceanic dolphins or Delphinidae are a widely distributed family of dolphins that live in the sea. Close to forty extant species are recognised. They include several big species whose common names contain "whale" rather than "dolphin", such as the Globicephalinae. Delphinidae is a family within the superfamily Delphinoidea, which also includes the porpoises (Phocoenidae) and the Monodontidae. River dolphins are relatives of the Delphinoidea.
The common dolphin is the most abundant cetacean in the world, with a global population of about six million. Despite this fact and its vernacular name, the common dolphin is not thought of as the archetypal dolphin, with that distinction belonging to the bottlenose dolphin due to its popular appearances in aquaria and the media. However, the common dolphin is often depicted in Ancient Greek and Roman art and culture, most notably in a mural painted by the Greek Minoan civilization.
The false killer whale is a species of oceanic dolphin that is the only extant representative of the genus Pseudorca. It is found in oceans worldwide but mainly in tropical regions. It was first described in 1846 as a species of porpoise based on a skull, which was revised when the first carcasses were observed in 1861. The name "false killer whale" comes from having a skull similar to the orca, or killer whale.
Humpback dolphins are members of the genus Sousa. These dolphins are characterized by the conspicuous humps and elongated dorsal fins found on the backs of adults of the species. Humpback dolphins inhabit shallow nearshore waters along coastlines across Australia, Africa, and Asia. Their preference for these habitats exposes them to various human activities such as fisheries entanglement, boat traffic, pollution, and habitat loss. Despite these risks, their nearshore presence facilitates easy observation from land.
The melon-headed whale, also known less commonly as the electra dolphin, little killer whale, or many-toothed blackfish, is a toothed whale of the oceanic dolphin family (Delphinidae). The common name is derived from the head shape. Melon-headed whales are widely distributed throughout deep tropical and subtropical waters worldwide, but they are rarely encountered at sea. They are found near shore mostly around oceanic islands, such as Hawaii, French Polynesia, and the Philippines.
The Atlantic spotted dolphin is a dolphin found in warm temperate and tropical waters of the Atlantic Ocean. Older members of the species have a very distinctive spotted coloration all over their bodies.
The common bottlenose dolphin or Atlantic bottlenose dolphin is one of three species of bottlenose dolphin in the genus Tursiops. The common bottlenose dolphin is a very familiar dolphin due to the wide exposure it receives in human care in marine parks and dolphinariums, and in movies and television programs. Common bottlenose dolphins inhabit temperate and tropical oceans throughout the world, 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.
Cetacean surfacing behaviour is a grouping of movement types that cetaceans make at the water's surface in addition to breathing. Cetaceans have developed and use surface behaviours for many functions such as display, feeding and communication. All regularly observed members of the order Cetacea, including whales, dolphins and porpoises, show a range of surfacing behaviours.
Cetacean bycatch is the accidental capture of non-target cetaceans such as dolphins, porpoises, and whales by commercial fisheries. Bycatch can be caused by entanglement in fishing nets and lines, or direct capture by hooks or in trawl nets.
The Tethys Research Institute is a non-profit research organisation founded in 1986 to support marine conservation through science and public awareness and by participating in the international conservation process. Tethys' activities are mainly carried out in the Mediterranean Sea, although research programmes have been conducted also in the Black Sea, the North Atlantic Ocean, the Caribbean, the Red Sea and Antarctica. The results of these activities have been presented in scientific publications as well as in meetings, workshops and conferences.
The Bottlenose Dolphin Research Institute (BDRI) is a research and educational centre dedicated to the understanding and conservation of cetaceans and the marine environment in which they live. The Institute's BDRI center was founded by the biologist Bruno Díaz López in Sardinia, Italy in 2005. In 2014, the BDRI opened a new facility in Galicia, Spain.
The Burrunan dolphin is a proposed species of bottlenose dolphin found in parts of Victoria, Australia first described in 2011. Its exact taxonomy is debated: numerous studies support it as being a separate species within the genus Tursiops and occupying a basal position within the genus, with limited phylogenetic studies using different methodologies indicate that it is a subspecies of the Indo-Pacific bottlenose dolphin. The Burrunan dolphin is not currently recognized as a species by the Society for Marine Mammalogy or American Society of Mammalogists, which cites problematic methodology in the original study proposing species status and recommends further research.
Bernd Gerhard Würsig is an educator and researcher who works mainly on aspects of behavior and behavioral ecology of whales and dolphins. Much of his early work was done in close collaboration with his wife Melany Ann Würsig, and they have published numerous manuscripts and books together. He is now Professor Emeritus at Texas A&M University, teaching only occasionally but still involved with graduate student and other research. He is especially active with problems and potential solutions concerning Indo-Pacific humpback dolphins, Sousa chinensis, in and surrounding waters of Hong Kong.
William F. Perrin was an American biologist specializing in the fields of cetacean taxonomy, reproductive biology, and conservation biology. He is best known for his work documenting the unsustainable mortality of hundreds of thousands of dolphins per year in the tuna purse-seine fishery of the eastern tropical Pacific. This work became a primary motivation for the U.S. Marine Mammal Protection Act (1972). His work on cetacean taxonomy was acknowledged in 2002 when a newly recognized species of beaked whale, Perrin's beaked whale, which was named in his honor.
1 2 3 4 5 6 7 Shirihai, H.; Jarrett, B. (2006). Whales Dolphins and Other Marine Mammals of the World. Princeton University Press. pp.159–161. ISBN978-0-691-12757-6.
↑ Möller Luciana M.; Beheregaray Luciano B (2001). "Coastal bottlenose dolphins from southeastern Australia are Tursiops aduncus according to sequences of the mitochondrial DNA control region". Marine Mammal Science. 17 (2): 249–263. Bibcode:2001MMamS..17..249M. doi:10.1111/j.1748-7692.2001.tb01269.x.
↑ Leduc, R.; Perrin, W. & Dizon, E. (18 August 1998). "Phylogenetic Relationships among the Delphinid Cetaceans Based on Full Cytochrome B Sequences". Marine Mammal Science. 15 (3): 619–648. doi:10.1111/j.1748-7692.1999.tb00833.x.
↑ Curry, B.E. and Smith, J. (1997) "Phylogeographic structure of the bottlenose dolphin (Tursiops truncatus): stock identification and implications for management", pp. 227–247 in: A.E. Dizon, S.J. Chivers, and W.F. Perrin (eds) Molecular Genetics of Marine Mammals. Society for Marine Mammalogy, Special Publication No. 3, Allen Press, Lawrence, Kansas.
1 2 3 Fisher Sue J.; Reeves Randall R. (2005). "The Global Trade in Live Cetaceans: Implications for Conservation". Journal of International Wildlife Law and Policy. 8 (4): 315–340. doi:10.1080/13880290500343624. S2CID84937276.
↑ Tadamichi, Morisaka; Masanori, Shinohara; Fumio, Nakahara; Tomonari, Akamatsu (2005). "Effects of Ambient Noise on the Whistles of Indo-Pacific Bottlenose Dolphin Populations". Journal of Mammalogy. 86 (3): 541–546. doi:10.1644/1545-1542(2005)86[541:eoanot]2.0.co;2. JSTOR4094322.
↑ Lemon Michelle; Lynch Tim P.; Cato Douglas H.; Harcourt Robert G (2006). "Response of traveling bottlenose dolphins (Tursiops aduncus) to experimental approaches by a powerboat in Jervis Bay, New South Wales, Australia". Biological Conservation. 127 (4): 363–372. Bibcode:2006BCons.127..363L. doi:10.1016/j.biocon.2005.08.016.
1 2 "Appendix IIArchived 11 June 2011 at the Wayback Machine " of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). As amended by the Conference of the Parties in 1985, 1988, 1991, 1994, 1997, 1999, 2002, 2005, and 2008. Effective: 5 March 2009.
↑ Temple, Andrew J., et al. "Spatial and temporal variations in the occurrence and foraging activity of coastal dolphins in Menai Bay, Zanzibar, Tanzania." PloS one 11.3 (2016): e0148995.
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