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Indian Ocean humpback dolphin

December 15, 2023

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]

Indian Ocean humpback dolphin[1]
Indian Ocean humpback dolphin（S. plumbea） off Khasab in Musandam
CITES Appendix I (CITES)[3]
Scientific classification
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)
S. plumbea range

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 edit

Distribution edit

Sousa plumbea ranges from Southern Africa to Western Indochina, including coastal areas along East Africa, the Middle East and India. 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.[5]

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.[6]

Habitat edit

Studies have determined that the most limiting factor to habitat-usage is water depth, with a majority of specimens typically remaining in shallow waters not exceeding 20 meters in depth. As a result, the Indian Ocean humpback dolphin's offshore range is largely dependent on the coastlines' specific physiographical characteristics.[7][8][6]

The species has been reported to inhabit a variety of different coastal habitats, including both soft sediment (e.g. sand and sea grass) and hard sediment (e.g. rock and coral) marine habitats as well as estuarine habitats (e.g. lagoons, bays, rivers, and mangrove channels). Preference and prominence of any given habitat type is highly dependent on the geographical location of any given Indian Ocean humpbacked dolphin population.[6]

Description edit

 
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).[9] They have a fatty hump on the back, which differentiates them from S. chinensis which have a more prominent dorsal fin, but no hump.[9]

Different varieties have different coloration, although young dolphins are generally gray, with darker gray above than below.[10] They are generally dark gray.[10]

Indian Ocean humpback dolphins can appear similar to conspecific Indo-Pacific bottlenose dolphins, but the bottlenose dolphins lack the hump.[9] 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.[9]

Life history edit

Growth rate edit

The Indian Ocean humpback dolphin is a medium-sized dolphin that exhibit a two-phase growth rate model, in which calves and juveniles experience dramatic growth before reaching a modal peak and after which growth rate slows down as they near complete physical maturity. This modal peak is predicted to occur at around the tenth year, with neonatal individuals averaging 100 cm and growing to an approximate 220 cm by the age of 10. Completely mature adults grow to an average total length of approximately 250 cm.[6][11]

Color pattern edit

Calves and juveniles less than a year old are typically unspotted and bear a grey coloration. Subadults slowly develop a "mottled" or "speckled" coating between the ages of 4 and 20, with females experiencing an earlier onset of this pattern development compared to males. After the age of 25, adults begin to slowly lose this spotted pattern and, once again, females experience an earlier onset and drastically faster rate of loss when compared to males.[11]

Reproduction edit

Females reach sexual maturity at an approximate age of 9 to 10 years, while males reach sexual maturity at an approximate age of 12 to 14 years.[12]

The Indian Ocean humpback dolphin exhibits a peak birthing season between the months of May and June, although they are capable of reproducing year round. This peak season, however, confers survival advantages to neonatal calves as it correlates with rising air and water temperatures during the later spring and early summer months.[6] Gestation lasts between 10 and 12 months. Observational studies have found that most females birth a single calf at any given reproductive period, after which they undergo a calving interval that averages approximately 62 months. This prolonged calving interval is in part due to a prolonged rearing period, in which calves are nursed by their mothers for a period of up to 24 months and mother-calf associations can last between 3 and 4 years.[6][11]

Despite this long rearing period, Indian Ocean humpback dolphins experience extremely high rates of infant mortality. Studies suggest that this heightened mortality is due to anthropogenic disturbances such as chemical pollution, habitat loss, fishing, and noise pollution.[11][5][13][14]

Sociality edit

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.[5]

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.[9][10]

Feeding edit

Very little is known on the specific species that compose the Indian Ocean humpback dolphin's diet, although multiple studies have confirmed that a majority of their diet is composed of sciaenid fishes, cephalopods, and crustaceans.[5][7]

A few studies have confirmed that Indian Ocean humpback dolphins perform a highly skilled and communal feeding behavior known as strand feeding, in which individuals collectively work together to herd fish onto exposed sand banks, after which they deliberately beach themselves to capture the beached fish.[5][15]

Conservation edit

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.[16][6] The most driving factor appears to be chemical pollution, as tissue analysis of many stranded specimens exhibit fatal concentrations of organochlorines.[13][14][17] 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.[18][19][20]

See also edit

References edit

  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. ^ a b 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. doi:10.1111/mms.12152.
  5. ^ a b c d e 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.
  6. ^ a b c d e f g 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.
  7. ^ a b Parra, Guido J.; Corkeron, Peter J.; Marsh, Helene (2004). "The Indo-Pacific Humpback Dolphin, Sousa chinensis (Osbeck, 1765), in Australian Waters: A Summary of Current Knowledge". Aquatic Mammals. 30 (1): 197–206. doi:10.1578/am.30.1.2004.197.
  8. ^ Karczmarski, Leszek; Cockcroft, Victor G.; Mclachlan, Anton (2000). "Habitat Use and Preferences of Indo-Pacific Humpback Dolphins Sousa Chinensis in Algoa Bay, South Africa". Marine Mammal Science. 16: 65–79. doi:10.1111/j.1748-7692.2000.tb00904.x. S2CID 84485298.
  9. ^ a b c d e Carwardine, M. (1995). Whales, Dolphins and Porpoises: The Visual Guide to All the World's Cetaceans. DK Publishing. pp. 174–175. ISBN 978-1564586209.
  10. ^ a b c 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.
  11. ^ a b c d Jefferson, Thomas A.; Hung, Samuel K.; Robertson, Kelly M.; Archer, Frederick I. (2012-01-01). "Life history of the Indo-Pacific humpback dolphin in the Pearl River Estuary, southern China". Marine Mammal Science. 28 (1): 84–104. doi:10.1111/j.1748-7692.2010.00462.x. ISSN 1748-7692. S2CID 55598663.
  12. ^ Jefferson, Thomas A. (2000). "Population Biology of the Indo-Pacific Hump-Backed Dolphin in Hong Kong Waters". Wildlife Monographs. 144 (144): 1–65. JSTOR 3830809.
  13. ^ a b 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.
  14. ^ a b 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.
  15. ^ M., Baldwin, Robert (1995). Whales and dolphins of the United Arab Emirates. Bowlish, Somerset, England: Published by Robert M. Baldwin. ISBN 978-0952660507. OCLC 43080658.{{cite book}}: CS1 maint: multiple names: authors list (link)
  16. ^ 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.
  17. ^ 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.
  18. ^ WAM. 2017. Abu Dhabi has world’s largest population of humpback dolphins. Emirates 24/7. Retrieved on September 21, 2017
  19. ^ Gulf News. 2017. Abu Dhabi proves a haven for humpback dolphins. Retrieved on September 21, 2017
  20. ^ Sanker A.. 2017. Abu Dhabi leads world in humpback dolphin numbers. Khaleej Times. Retrieved on September 21, 2017

December 15, 2023
indian, ocean, humpback, dolphin, sousa, plumbea, member, delphinidae, family, occupying, coastal, areas, ranging, from, southern, africa, western, indochina, indo, pacific, humpback, dolphin, sousa, chinensis, formerly, included, within, same, species, 2014, . 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 Indian Ocean humpback dolphin 1 Indian Ocean humpback dolphin S plumbea off Khasab in MusandamConservation statusEndangered IUCN 3 1 2 CITES Appendix I CITES 3 Scientific classificationDomain EukaryotaKingdom AnimaliaPhylum ChordataClass MammaliaOrder ArtiodactylaInfraorder CetaceaFamily DelphinidaeGenus SousaSpecies S plumbeaBinomial nameSousa plumbea G Cuvier 1829 S plumbea rangeThe 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 Contents 1 Distribution and habitat 1 1 Distribution 1 2 Habitat 2 Description 3 Life history 3 1 Growth rate 3 2 Color pattern 3 3 Reproduction 4 Sociality 5 Feeding 6 Conservation 7 See also 8 ReferencesDistribution and habitat editDistribution edit Sousa plumbea ranges from Southern Africa to Western Indochina including coastal areas along East Africa the Middle East and India 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 5 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 6 Habitat edit Studies have determined that the most limiting factor to habitat usage is water depth with a majority of specimens typically remaining in shallow waters not exceeding 20 meters in depth As a result the Indian Ocean humpback dolphin s offshore range is largely dependent on the coastlines specific physiographical characteristics 7 8 6 The species has been reported to inhabit a variety of different coastal habitats including both soft sediment e g sand and sea grass and hard sediment e g rock and coral marine habitats as well as estuarine habitats e g lagoons bays rivers and mangrove channels Preference and prominence of any given habitat type is highly dependent on the geographical location of any given Indian Ocean humpbacked dolphin population 6 Description edit nbsp S plumbea off Khasab in MusandamThe 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 9 They have a fatty hump on the back which differentiates them from S chinensis which have a more prominent dorsal fin but no hump 9 Different varieties have different coloration although young dolphins are generally gray with darker gray above than below 10 They are generally dark gray 10 Indian Ocean humpback dolphins can appear similar to conspecific Indo Pacific bottlenose dolphins but the bottlenose dolphins lack the hump 9 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 9 Life history editGrowth rate edit The Indian Ocean humpback dolphin is a medium sized dolphin that exhibit a two phase growth rate model in which calves and juveniles experience dramatic growth before reaching a modal peak and after which growth rate slows down as they near complete physical maturity This modal peak is predicted to occur at around the tenth year with neonatal individuals averaging 100 cm and growing to an approximate 220 cm by the age of 10 Completely mature adults grow to an average total length of approximately 250 cm 6 11 Color pattern edit Calves and juveniles less than a year old are typically unspotted and bear a grey coloration Subadults slowly develop a mottled or speckled coating between the ages of 4 and 20 with females experiencing an earlier onset of this pattern development compared to males After the age of 25 adults begin to slowly lose this spotted pattern and once again females experience an earlier onset and drastically faster rate of loss when compared to males 11 Reproduction edit Females reach sexual maturity at an approximate age of 9 to 10 years while males reach sexual maturity at an approximate age of 12 to 14 years 12 The Indian Ocean humpback dolphin exhibits a peak birthing season between the months of May and June although they are capable of reproducing year round This peak season however confers survival advantages to neonatal calves as it correlates with rising air and water temperatures during the later spring and early summer months 6 Gestation lasts between 10 and 12 months Observational studies have found that most females birth a single calf at any given reproductive period after which they undergo a calving interval that averages approximately 62 months This prolonged calving interval is in part due to a prolonged rearing period in which calves are nursed by their mothers for a period of up to 24 months and mother calf associations can last between 3 and 4 years 6 11 Despite this long rearing period Indian Ocean humpback dolphins experience extremely high rates of infant mortality Studies suggest that this heightened mortality is due to anthropogenic disturbances such as chemical pollution habitat loss fishing and noise pollution 11 5 13 14 Sociality editThe 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 5 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 9 10 Feeding editVery little is known on the specific species that compose the Indian Ocean humpback dolphin s diet although multiple studies have confirmed that a majority of their diet is composed of sciaenid fishes cephalopods and crustaceans 5 7 A few studies have confirmed that Indian Ocean humpback dolphins perform a highly skilled and communal feeding behavior known as strand feeding in which individuals collectively work together to herd fish onto exposed sand banks after which they deliberately beach themselves to capture the beached fish 5 15 Conservation editThe 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 16 6 The most driving factor appears to be chemical pollution as tissue analysis of many stranded specimens exhibit fatal concentrations of organochlorines 13 14 17 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 18 19 20 See also edit nbsp Cetaceans portal nbsp Mammals portal nbsp Marine life portalList of cetaceansReferences edit 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 a b 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 Appendices CITES cites org Retrieved 2022 01 14 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 doi 10 1111 mms 12152 a b c d e 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 a b c d e f g Jefferson Thomas A Karczmarski Leszek 2001 01 01 Sousa chinensis Mammalian Species 655 1 9 doi 10 1644 1545 1410 2001 655 lt 0001 sc gt 2 0 co 2 ISSN 0076 3519 S2CID 198968876 a b Parra Guido J Corkeron Peter J Marsh Helene 2004 The Indo Pacific Humpback Dolphin Sousa chinensis Osbeck 1765 in Australian Waters A Summary of Current Knowledge Aquatic Mammals 30 1 197 206 doi 10 1578 am 30 1 2004 197 Karczmarski Leszek Cockcroft Victor G Mclachlan Anton 2000 Habitat Use and Preferences of Indo Pacific Humpback Dolphins Sousa Chinensis in Algoa Bay South Africa Marine Mammal Science 16 65 79 doi 10 1111 j 1748 7692 2000 tb00904 x S2CID 84485298 a b c d e Carwardine M 1995 Whales Dolphins and Porpoises The Visual Guide to All the World s Cetaceans DK Publishing pp 174 175 ISBN 978 1564586209 a b c 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 a b c d Jefferson Thomas A Hung Samuel K Robertson Kelly M Archer Frederick I 2012 01 01 Life history of the Indo Pacific humpback dolphin in the Pearl River Estuary southern China Marine Mammal Science 28 1 84 104 doi 10 1111 j 1748 7692 2010 00462 x ISSN 1748 7692 S2CID 55598663 Jefferson Thomas A 2000 Population Biology of the Indo Pacific Hump Backed Dolphin in Hong Kong Waters Wildlife Monographs 144 144 1 65 JSTOR 3830809 a b 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 a b 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 M Baldwin Robert 1995 Whales and dolphins of the United Arab Emirates Bowlish Somerset England Published by Robert M Baldwin ISBN 978 0952660507 OCLC 43080658 a href Template Cite book html title Template Cite book cite book a CS1 maint multiple names authors list link 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 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 WAM 2017 Abu Dhabi has world s largest population of humpback dolphins Emirates 24 7 Retrieved on September 21 2017 Gulf News 2017 Abu Dhabi proves a haven for humpback dolphins Retrieved on September 21 2017 Sanker A 2017 Abu Dhabi leads world in humpback dolphin numbers Khaleej Times Retrieved on September 21 2017 Retrieved from https en wikipedia org w index php title Indian Ocean humpback dolphin amp oldid 1116596550, wikipedia, wiki, book, books, library,

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