Humpback Dolphin
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Humpback dolphins are members of the
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''Sousa''. These
dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...
s are characterized by the conspicuous humps and elongated
dorsal fin A dorsal fin is a fin on the back of most marine and freshwater vertebrates. Dorsal fins have evolved independently several times through convergent evolution adapting to marine environments, so the fins are not all homologous. They are found ...
s found on the backs of adults of the species. Humpback dolphins inhabit shallow nearshore waters along coastlines across
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
,
Africa Africa is the world's second-largest and second-most populous continent after Asia. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 20% of Earth's land area and 6% of its total surfac ...
, and
Asia Asia ( , ) is the largest continent in the world by both land area and population. It covers an area of more than 44 million square kilometres, about 30% of Earth's total land area and 8% of Earth's total surface area. The continent, which ...
. 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. There are four recognized species: the Indo-Pacific humpback dolphin (''Sousa chinensis''), Indian Ocean humpback dolphin ''(S. plumbea''), Atlantic humpback dolphin ''(S. teuszii''), and Australian humpback dolphin ''(S. sahulensis''). Although generally shy and less active compared to bottlenose dolphins, they are occasionally featured in dolphin watching tours, particularly in locations like
Hong Kong Hong Kong)., Legally Hong Kong, China in international treaties and organizations. is a special administrative region of China. With 7.5 million residents in a territory, Hong Kong is the fourth most densely populated region in the wor ...
and the
Musandam Peninsula The Musandam Peninsula (), locally known as Ruus Al Jibal ( Capes of the Mountains), is a peninsula that forms the northeastern point of the Arabian Peninsula. Geography The peninsula lies to the south of the Strait of Hormuz, between the Persia ...
of
Oman Oman, officially the Sultanate of Oman, is a country located on the southeastern coast of the Arabian Peninsula in West Asia and the Middle East. It shares land borders with Saudi Arabia, the United Arab Emirates, and Yemen. Oman’s coastline ...
.


Description

The humpback dolphin is a coastal species found from Africa and India south to Australia, with variations in different regions. It has a distinctive hump in front of its dorsal fin and a keel on its belly. The dorsal fin is somewhat curved. Its pectoral fins are relatively small, and the tail flukes have a noticeable notch in the middle. Each side of its jaw has 30 to 34 small, cone-shaped teeth. They feature a long
rostrum Rostrum may refer to: * Any kind of a platform for a speaker: **dais **pulpit ** podium * Rostrum (anatomy), a beak, or anatomical structure resembling a beak, as in the mouthparts of many sucking insects * Rostrum (ship), a form of bow on naval ...
, which constitutes 6.3–10.1% of their body length. Their bodies are robust, tapering towards the rear, with distinct keels on both the dorsal and ventral sides of the caudal peduncle across all age groups. Neonatal lengths in South African waters range from 97 to 108 cm, with maximum recorded lengths up to 2.8 m. Among ''Sousa'' species, ''Sousa plumbea'' is the largest, with reported lengths exceeding 3.0 m in the Arabian and Indian regions, although some dispute these reports. Southern African dolphin calves have a lighter coloration compared to adults. Calves exhibit pale grey coloration on their flanks with a whiter ventral side, transitioning to darker grey on their back and upper flukes. A diffuse grey stripe runs from the eye towards the flipper, while the dorsal and ventral keels of the caudal peduncle appear off-white. This color pattern persists into adulthood but darkens over time, with some of the largest adults showing white areas on the dorsal fin and hump. Many individuals exhibit prominent scars on their dorsal fin and back, believed to result from unsuccessful shark attacks. The species is characterized by smaller organ weights, indicating it is a shallow-diving, relatively slow-moving coastal delphinid compared to species like the Indo-Pacific bottlenose dolphins (''Tursiops aduncus'') and long-beaked common dolphins (''Delphinus capensis''). Research has been most extensive in South African populations in Algoa Bay and Richards Bay, although these may not fully represent other populations in the subregion.


Diet

Studies on the diet of Humpback dolphins have mostly been restricted to individuals either stranded on shore or caught in shark nets. They feed almost exclusively on fish, although they have been known to occasionally prey on cephalopods as well. These dolphins mainly eat fish that live near reefs, in estuaries, and on the ocean floor. A study from 1983 examining the stomachs of 17 humpback dolphins found that glassnosed anchovy (''Thryssa vitrirostris'') was the most common prey, followed by ribbon fish (''Trichiurus lepturus''), olive grunter (''Pomadasys olivaceum''), and longtooth kob (''Otolithes ruber''). A study of Humpback dolphins stranded in Hong Kong from 1994-2000 had similar results, with the addition of cutlassfishes, sardines, mullets, and catfish. The presence of catfish as prey is notable due to their venomous spines, which have been implicated in the deaths of dolphins elsewhere. A more recent study in 2013 analyzing the stomach contents of 22 humpback dolphins (13 males, 9 females) caught in shark nets in the KwaZulu-Natal Coastline identified 59 different prey species. The main prey species were similar to those found earlier, with the addition of the bearded croaker (''Johnius amblycephalus''). Humpback dolphins employ diverse feeding strategies, such as beaching themselves partially to chase after fish. Additionally, in certain areas, these dolphins are observed trailing fishing trawlers to exploit discarded or escaped fish as a feeding opportunity. Though this behavior may conserve energy and supplement their diet, it also exposes them to risk of entanglement in nets. Two dolphins suspected of being caught in trawler nets (SC96-31/05 and SC97-31/5B) were found with undigested fish and nearly full stomachs, including significant quantities of prey species like ''Johnius'' and ''Collichthys lucida'', commonly caught by trawlers.


Taxonomy

* Genus ''Sousa'': ** ''S. chinensis'' ( Indo-Pacific humpback dolphin) ** ''S. plumbea'' ( Indian Ocean humpback dolphin) ** ''S. teuszii'' ( Atlantic humpback dolphin) ** ''S. sahulensis'' ( Australian humpback dolphin) By the mid-2000s, most authorities accepted just two species—the Atlantic and the
Indo-Pacific The Indo-Pacific is a vast biogeographic region of Earth. In a narrow sense, sometimes known as the Indo-West Pacific or Indo-Pacific Asia, it comprises the tropical waters of the Indian Ocean, the western and central Pacific Ocean, and the ...
. However, in his widely used systematic account, Rice identified three species, viewing the Indo-Pacific as two species named simply the Indian and Pacific. The dividing line between the two (sub)species is taken to be
Sumatra Sumatra () is one of the Sunda Islands of western Indonesia. It is the largest island that is fully within Indonesian territory, as well as the list of islands by area, sixth-largest island in the world at 482,286.55 km2 (182,812 mi. ...
, one of the
Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania, between the Indian Ocean, Indian and Pacific Ocean, Pacific oceans. Comprising over List of islands of Indonesia, 17,000 islands, including Sumatra, ...
n islands; however, intermixing is thought to be inevitable. Further,
Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...
n cetologist Graham Ross writes "However, recent morphological studies, somewhat supported equivocally by genetic analyses, indicate that there is a single, variable species for which the name ''S. chinensis'' has priority".''Humpback Dolphins'' Graham J. B. Ross pps 585-589 in ''Encyclopedia of Marine Mammals'' (1998) Humpback dolphins found in Chinese waters are locally known as Chinese white dolphins. See that article for specific issues relating to that subspecies which corresponds to the Pacific humpback dolphin in Rice's classification. In late 2013, researchers from the Wildlife Conservation Society and the American Natural History museum proposed classification of the Indo-Pacific humpback dolphin into three species based on morphological and genetic analysis. Their research indicates that at least four species make up the genus ''Sousa'': the Atlantic humpback dolphin (''S. teuszii''), two species of Indo-Pacific humpback dolphin (''S. plumbea'' and ''S. chinesis''), and a fourth, new species of Indo-Pacific humpback dolphin found off northern Australia, a distinction with potential to guide conservation efforts for the species.


Conservation

''S. teuszii'' is listed on Appendix IAppendix I and Appendix II
" 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.
and Appendix II (along with ''S. chinensis)'' of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). It is listed on Appendix I as this species has been categorized as being in danger of extinction throughout all or a significant proportion of its range and CMS Parties strive towards strictly protecting these animals, conserving or restoring the places where they live, mitigating obstacles to migration and controlling other factors that might endanger them. It is listed on Appendix II as it has an unfavourable conservation status or would benefit significantly from international co-operation organised by tailored agreements. In addition, the Atlantic humpback dolphin is covered by the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia.Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia
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See also

*
List of cetacean species Cetacea is an infraorder that comprises the 94 species of whales, dolphins, and porpoises. It is divided into toothed whales (Odontoceti) and baleen whales (Mysticeti), which diverged from each other in the Eocene some 50 mya (unit), million years ...


References

{{Taxonbar, from=Q309999 Oceanic dolphins Cetaceans of the Pacific Ocean Cetaceans of the Indian Ocean Cetaceans of the Atlantic Ocean Marine fauna of Africa Marine fauna of Asia Marine fauna of Oceania Mammals of Asia Taxa named by John Edward Gray