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NRLD - 329853 | Tursiops truncatus

Assessment ID
329853
Taxon name
Tursiops truncatus
(Montagu, 1821)
Uploaded by
National Red List Database
Taxonomic information
Scientific name
Tursiops truncatus
(Montagu, 1821)
Assessed taxon level
Species
Higher level taxonomic groupings
Vertebrates
Mammals
Kingdom
Animalia
Phylum
chordata
Class
mammalia
Order
cetartiodactyla
Family
delphinidae
Genus
Tursiops
Species
truncatus
Species authority
(Montagu, 1821)
Taxonomic notes and synonyms listed
All Bottlenose Dolphins around the world were previously recognized as Tursiops truncatus, but currently, the genus is considered to be composed of two species: T. truncatus (Common Bottlenose Dolphin) and T. aduncus (the smaller Indo-Pacific Bottlenose Dolphin) (Wang et al. 1999, 2000a,b). The Common Bottlenose Dolphin has a worldwide distribution in tropical and temperate latitudes but exhibits a strong ability to adapt to local conditions, a complex social structure and strong site fidelity which results in considerable habitat partitioning throughout its range. This, in turn, has created strong population differentiation accompanied, in some cases, by marked morphological differentiation. The taxonomy of Bottlenose Dolphins is confused due to this geographical variation, and it is very possible that additional species will be recognized in the future. Three subspecies are currently recognized by the Society for Marine Mammalogy's Committee on Taxonomy (2017) and a recent re-assessment of Tursiops taxonomy worldwide conducted by the International Whaling Commission confirmed their validity (IWC 2018). These subspecies are the Black Sea Bottlenose Dolphin (T. t. ponticus Barabash-Nikiforov, 1940) which differs morphologically and genetically from other forms including those in the nearby Mediterranean Sea (Barabash-Nikiforov 1960, Geptner et al. 1976, Natoli et al. 2005, Viaud-Martinez et al. 2008). The Lahille Bottlenose Dolphin (T. t. gephyreus) (Lahille, 1908), a larger form in the coastal waters of the western South Atlantic Ocean, is morphologically and genetically different from the offshore population in eastern South America (Costa et al. 2015, 2016; Fruet et al. 2011, 2015). The third subspecies is the nominate subspecies that includes the remaining Common Bottlenose Dolphins worldwide (T. t. truncatus (Montagu, 1821)). In the western North Atlantic, two forms, offshore and coastal, are distinguishable on the basis of morphology and ecological markers (Mead and Potter 1995) and have fixed genetic differences (Le Duc and Curry 1997, Hoelzel et al. 1998, Kingston et al. 2009, Rosel et al. 2009, Van Waerebeek et al. 2017a) and according to the recent IWC review the coastal population should be recognized as at least a different subspecies.
Location and scope
Specific locality or subnational name or regional name
United Arab Emirates (the)
Scope (of the Assessment)
National
Countries included within the scope of the assessment
United Arab Emirates (the)
Country ISO code(s)
ARE
Does the assessment cover a marine EEZ area(s)?
Not_assigned
Conservation Status
Assessed as
Data deficient
Abbreviated status
DD
Criteria system used
IUCN

(see Assessment details)

Assessment rationale/justification
There is currently no information available on the population size and trends, hence it is assessed as Data Deficient (DD). Until recently this species was thought to be more widespread in the UAE waters, but it is now known that the species found in the Gulf should be treated as Tursiops aduncus (many specimens from the Gulf were misidentified as T. truncatus). There is potential for a rescue effect, but as the species is listed as DD, that regional assessment cannot be adjusted.
Assessment details
Year assessed
2018
Assessors/contributors/reviewers listed
UAE National Red List Workshop
Criteria system used
IUCN
Reference for methods given
IUCN. 2012. IUCN Red List Categories and Criteria: Version 3.1, Second edition. IUCN, Gland, Switzerland and Cambridge, UK. iv + 32pp pp. And IUCN. 2012. Guidelines for Application of IUCN Red List Criteria at Regional and National Levels: Version 4.0. Gland, Switzerland and Cambridge, UK: IUCN. iii + 41pp.
Further information
Endemism (according to assessment)
Endemic to region
Not assigned
Taxon distribution as listed in assessment
The species occurs in the Gulf of Oman, but is apparently absent from the Arabian Gulf, reflecting a preference for deep, offshore water. Globally, this species is distributed through all tropical and temperate inshore, coastal, shelf, and oceanic waters (Hammond et al. 2012d).
Is there a map available in assessment?
Yes
Habitat and systems
Ecological system type
Terrestrial
Not_assigned
Freshwater
Not_assigned
Marine
Not_assigned
Habitat
Habitat details as listed in assessment
Typically, Common Bottlenose Dolphins are found in groups of 5-“35 individuals in the UAE, although much larger groups can occur. They are fast, powerful swimmers, often riding the bow wave of boats. As their reputation in aquaria attests, they are inquisitive and capable of spectacular aerial acrobatics. Common Bottlenose Dolphins have been observed feeding in deep water off the east coast (500-“2,000 m) (Baldwin 2005).
Threats and conservation measures listed
Threats listed in assessment
The main threats to cetaceans in UAE waters include: incidental mortality in trawl, drift and anchored gill nets, depletion of prey populations (due in part to commercial overfishing); ship and boat strikes, disturbance due to underwater noise (including that from vessel traffic, drilling, piling, military operations and seismic activity related to offshore oil and gas exploration). A lack of information (e.g. population size and trend, the location of critical habitats, and feeding ecology) hinders the development of appropriate conservation actions, but this should be used as an excuse for inaction.
History
The backcasted 1996 assessment for this species is Data Deficient. Hornby (1996) assessed the status of both Tursiops species under a combined taxonomic concept using the name ""T. truncatus"" and listed it as Near Threatened; as it is a different concept that assessment cannot be used.
Publication
Mallon, D., Hilton-Taylor, C., Allen, D., & Harding, K. (2019). UAE National Red List of Mammals: Marine and Terrestrial. A report to the Ministry of Climate Change and Environment, United Arab Emirates (p. 41). IUCN Global Species Programme. https://bit.ly/2RdZCQR