Indian Ocean humpback dolphin

Last updated

Indian Ocean humpback dolphin [1]
Dolphin-Musandam 2.jpg
Indian Ocean humpback dolphin(S. plumbea) off Khasab in Musandam
CITES Appendix I (CITES) [3]
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Delphinidae
Genus: Sousa
Species:
S. plumbea
Binomial name
Sousa plumbea
(G. Cuvier, 1829)
Cetacea range map Indian Humpback Dolphin.PNG
S. plumbea range

The Indian Ocean humpback dolphin (Sousa plumbea) is a member of the Delphinidae family occupying coastal areas ranging from Southern Africa to Western Indochina. The Indo-Pacific humpback dolphin (Sousa chinensis) was formerly included within the same species, but a 2014 study revealed them to be a separate species. [4]

Contents

The most limiting factor to habitat-usage is water depth, with most specimens remaining in waters shallower than 20 meters. As a result, the Indian Ocean humpback dolphin's offshore range is largely dependent on the coastlines' specific physiographical characteristics. The species has been reported to inhabit nearly every type of coastal habitat, although preference and prominence of any given habitat type is highly dependent on the geographical location. Indian Ocean humpback dolphins experience extremely high rates of calf and juvenile mortality due to anthropogenic disturbances such as environmental pollution, habitat deterioration and noise pollution.

Indian Ocean humpback dolphins are social delphinids that live in groups averaging twelve individuals, although group size can be highly variable. The majority of their diet is composed of sciaenid fishes, cephalopods, and crustaceans.

The species is currently categorized as Endangered. [2]

Distribution and habitat

Distribution

Sousa plumbea ranges from Southern Africa to Western Indochina, including coastal areas along East Africa, the Middle East and India. There is studied population in Menai Bay Conservation Area of Tanzania's Zanzibar Archipelago. [5] Critically important populations have been determined in Southeast Asia, particularly along the southern coastlines of China. Recent investigations have, however, similarly determined critical populations along the coasts of the Arabian peninsula, particularly including the Sultanate of Oman and the United Arab Emirates. [6]

While S. plumbea and S. chinensis are genetically distinguishable, delphinids' high capacity for hybridization have resulted in hybrid populations in areas of overlapping distribution. In fact, genetic analysis has indicated that S. chinensis sampled from Indochina are more closely related to S. plumbea than to S. chinensis from Australia.

This species does not exhibit large migratory behavior. [7]

Description

S. plumbea off Khasab in Musandam Dolphin-Musandam 2.jpg
S. plumbea off Khasab in Musandam

The Indian Ocean humpback dolphin is a medium-sized dolphin that ranges in length from 2 to 2.8 metres (6.6 to 9.2 ft) and in weight from 150 to 200 kilograms (330 to 440 lb). [8] They have a fatty hump on the back, which differentiates them from S. chinensis which have a more prominent dorsal fin, but no hump. [8]

Different varieties have different coloration, although young dolphins are generally gray, with darker gray above than below. [9] They are generally dark gray. [9]

Indian Ocean humpback dolphins can appear similar to conspecific Indo-Pacific bottlenose dolphins, but the bottlenose dolphins lack the hump. [8] All humpback dolphins have a distinctive motion when surfacing, in that it surfaces at a 30- to 45-degree angle with the rostrum, and sometimes the full head, showing before arching its back and sometimes showing its flukes. [8]

Life history

Sociality

The Indian Ocean humpback dolphin is a social delphinid that typically lives within a group. Group size is, however, highly variable. Some specimens have been found to be isolated individuals, although the average group is composed of around 12 individuals and some of the largest observed groups have been in excess of 100 individuals. [6]

There is very little scientific evidence to support significant inter-species interactions and groupings, although rare observations have noted interactions (both friendly and aggressive) with the sympatric Indo-Pacific bottlenose dolphin, snubfin dolphin, long-snouted spinner dolphin and finless porpoise. [8] [9]

Conservation

The Indian Ocean humpback dolphin has proven to be particularly susceptible to the deleterious effects of anthropogenic activity. The species' shallow, coastal habitat heightens their exposure to anthropogenic disturbances such as habitat deterioration, mortality due to by-catch, vessel striking, and noise pollution. [10] [7] The most driving factor appears to be chemical pollution, as tissue analysis of many stranded specimens exhibit fatal concentrations of organochlorines. [11] [12] [13] As a result, a number of nations have preemptively established conservation and management programs to ensure that the species' does not become endangered.

Recent investigative studies have revealed that the United Arab Emirates houses one of the world's largest populations. [14] [15] [16]

See also

Related Research Articles

<span class="mw-page-title-main">Indo-Pacific humpback dolphin</span> Species of mammal

The Indo-Pacific humpback dolphin is a species of humpback dolphin inhabiting coastal waters of the eastern Indian and western Pacific Oceans. This species is often referred to as the Chinese white dolphin in mainland China, Macau, Hong Kong, Singapore and Taiwan as a common name. Some biologists regard the Indo-Pacific dolphin as a subspecies of the Indian Ocean humpback dolphin which ranges from East Africa to India. However, DNA testing studies have shown that the two are distinct species. A new species, the Australian humpback dolphin, was split off from S. chinensis and recognized as a distinct species in 2014. Nevertheless, there are still several unresolved issues in differentiation of the Indian Ocean-type and Indo-Pacific-type humpback dolphins.

<span class="mw-page-title-main">Oceanic dolphin</span> Family of marine mammals

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.

<span class="mw-page-title-main">Indo-Pacific finless porpoise</span> Species of porpoise

The Indo-Pacific finless porpoise is one of eight porpoise species. The species ranges throughout most of the Indian Ocean, as well as the tropical and subtropical Pacific from Indonesia north to the Taiwan Strait. Overlapping with this species in the Taiwan Strait and replacing it northwards is the East Asian finless porpoise.

<span class="mw-page-title-main">Common dolphin</span> Species of mammal

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.

<i>Orcaella</i> Genus of mammals

The snubfin dolphins (Orcaella) are a genus of cetaceans containing two members: the Irrawaddy dolphin and the Australian snubfin dolphin. The genus was long believed to be monotypic with the only species being the Irrawaddy dolphin; however, in 2005, supposed Irrawaddy dolphin populations inhabiting the Australian/New Guinean regions were found to be significantly different and were declared a separate new species named the Australian snubfin dolphin.

<span class="mw-page-title-main">Indo-Pacific bottlenose dolphin</span> Species of mammal

The Indo-Pacific bottlenose dolphin is a species of bottlenose dolphin. This dolphin grows to 2.6 m (8.5 ft) long, and weighs up to 230 kg (510 lb). It lives in the waters around India, northern Australia, South China, the Red Sea, and the eastern coast of Africa. Its back is dark grey and its belly is lighter grey or nearly white with grey spots.

<span class="mw-page-title-main">Humpback dolphin</span> Genus of mammals

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. They are found close to shore along the coast of West Africa and right along the coast of the Indian Ocean from South Africa to Australia. Several institutions have made a proposal to divide the Indo-Pacific species into two distinct species: the Indo-Pacific humpback dolphin and the Australian humpback dolphin.

<span class="mw-page-title-main">Atlantic humpback dolphin</span> Species of mammal

The Atlantic humpback dolphin is a species of humpback dolphin that is found in coastal areas of West Africa.

<span class="mw-page-title-main">Melon-headed whale</span> Species of mammal

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.

<span class="mw-page-title-main">Fraser's dolphin</span> Species of mammal

Fraser's dolphin or the Sarawak dolphin is a cetacean in the family Delphinidae found in deep waters in the Pacific Ocean and to a lesser extent in the Indian and Atlantic Oceans.

<span class="mw-page-title-main">Common bottlenose dolphin</span> Species of dolphin

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 captivity 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.

<span class="mw-page-title-main">Cetacean surfacing behaviour</span> Cetacean movement types

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.

<span class="mw-page-title-main">Cetacean bycatch</span> Accidental capture of porpoises, whales and dolphins

Cetacean bycatch is the accidental capture of non-target cetacean species such as dolphins, porpoises, and whales by fisheries. Bycatch can be caused by entanglement in fishing nets and lines, or direct capture by hooks or in trawl nets.

<span class="mw-page-title-main">Australian snubfin dolphin</span> Species of mammal

The Australian snubfin dolphin is a dolphin found off the northern coasts of Australia. It closely resembles the Irrawaddy dolphin and was not described as a separate species until 2005. The closest relative to the genus Orcaella is the killer whale, Orcinus orca. The Australian snubfin has three colors on its skin, while the Irrawaddy dolphin only has two. The skull and the fins also show minor differences between the two species.

<span class="mw-page-title-main">Menai Bay</span> Coastal bay in Tanzania


Menai Bay is a bay in Mkinga District of Mjini Magharibi Region of Tanzania. The bay is geogrpahically part of the Zanzibar Archipelago.

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.

<span class="mw-page-title-main">Bernd Würsig</span> Marine mammal behavioral ecologist

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.

<span class="mw-page-title-main">Australian humpback dolphin</span> Species of mammal

The Australian humpback dolphin is a species of humpback dolphin and the fourth recognized humpback dolphin species chronologically. The specific name sahulensis is derived from the Sahul Shelf, located between northern Australia and southern New Guinea, where the Australian humpback dolphins occur.

References

  1. Mead, J. G.; Brownell, R. L. Jr. (2005). "Order Cetacea". In Wilson, D. E.; Reeder, D. M. (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 732. ISBN   978-0-8018-8221-0. OCLC   62265494.
  2. 1 2 Braulik, G.T.; Findlay, K.; Cerchio, S.; Baldwin, R.; Perrin, W. (2017). "Sousa plumbea". IUCN Red List of Threatened Species . 2017: e.T82031633A82031644. doi: 10.2305/IUCN.UK.2017-3.RLTS.T82031633A82031644.en . Retrieved 12 November 2021.
  3. "Appendices | CITES". cites.org. Retrieved 2022-01-14.
  4. Jefferson, Thomas A.; Rosenbaum, Howard C. (2014). "Taxonomic revision of the humpback dolphins (Sousa spp.), and description of a new species from Australia". Marine Mammal Science. 30 (4): 1494–1541. Bibcode:2014MMamS..30.1494J. doi:10.1111/mms.12152.
  5. 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.
  6. 1 2 Baldwin, Robert M.; Collins, Moth; Waerebeek, Koen Van; Minton, Gianna (2004). "The Indo-Pacific Humpback Dolphin of the Arabian Region: A Status Review". Aquatic Mammals. 30 (1): 111–124. doi:10.1578/am.30.1.2004.111.
  7. 1 2 Jefferson, Thomas A.; Karczmarski, Leszek (2001-01-01). "Sousa chinensis". Mammalian Species. 655: 1–9. doi:10.1644/1545-1410(2001)655<0001:sc>2.0.co;2. ISSN   0076-3519. S2CID   198968876.
  8. 1 2 3 4 5 Carwardine, M. (1995). Whales, Dolphins and Porpoises: The Visual Guide to All the World's Cetaceans . DK Publishing. pp.  174–175. ISBN   978-1564586209.
  9. 1 2 3 Wells, R.; Scott, M. (2002). "Humpback Dolphins". In Para, G.J.; Ross, G.J.B (eds.). Encyclopedia of Marine Mammals. Academic Press. pp.  576–581. ISBN   978-0-12-551340-1.
  10. Karczmarski, Leszek (2000-07-01). "Conservation and management of humpback dolphins: the South African perspective". Oryx. 34 (3): 207–216. doi: 10.1046/j.1365-3008.2000.00120.x . ISSN   1365-3008.
  11. Parsons, E.C.M; Chan, L. (1998). "Organochlorines in Indo-Pacific hump-backed dolphins (Sousa chinensis) and finless porpoises (Neophocaena phocaenoides) from Hong Kong". The Marine Biology of the South China Sea. 3: 423–437 via ResearchGate.
  12. Jefferson, Thomas A.; Hung, Samuel K.; Lam, Paul K.S. (2006). "Strandings, mortality and morbidity of Indo-Pacific humpback dolphins in Hong Kong, with emphasis on the role of organochlorine contaminants" (PDF). Journal of Cetacean Research and Management. 8: 181–193.
  13. Parsons, E.C.M. (2004). "The Potential Impacts of Pollution on Humpback Dolphins, with a Case Study on the Hong Kong Population". Aquatic Mammals. 30 (1): 18–37. doi:10.1578/am.30.1.2004.18.
  14. WAM. 2017. Abu Dhabi has world’s largest population of humpback dolphins. Emirates 24/7. Retrieved on September 21, 2017
  15. Gulf News. 2017. Abu Dhabi proves a haven for humpback dolphins. Retrieved on September 21, 2017
  16. Sanker A.. 2017. Abu Dhabi leads world in humpback dolphin numbers. Khaleej Times. Retrieved on September 21, 2017