Taxon name
Tursiops aduncus
(Ehrenberg, 1833)
Uploaded by
National Red List Database
Taxonomic information
Scientific name
Tursiops aduncus
(Ehrenberg, 1833)
Assessed taxon level
Species
Higher level taxonomic groupings
Vertebrates
Mammals
Species authority
(Ehrenberg, 1833)
Taxonomic notes and synonyms listed
The Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) has been recognized as a different species from the more widely distributed Common Bottlenose Dolphin (Tursiops truncatus) since the late 1990's (Rice, 1998). Indo-Pacific Bottlenose Dolphins are distinct from Common Bottlenose Dolphins based on concordance among genetic, osteology, coloration and external morphology data (Wang et al. 1999, 2000a,b). No Indo-Pacific Bottlenose Dolphin subspecies are currently recognised by the Society for Marine Mammalogy's Committee on Taxonomy (2018). However, a recent re-assessment of Tursiops taxonomy worldwide (IWC 2019) and extensive genetic studies (Moura et al. 2013, Amaral et al. 2016, Gray et al. 2018) identified 4 or 5 different lineages (Africa, Pakistan, Bay of Bengal, China and Australia), including the recently described ""T. australis"" (Charlton-Robb et al., 2011) that may eventually be recognized as a subspecies. There is considerable population structure throughout the range of the species and multiple studies of morphology (Hale et al., 2000, Kemper 2004, Charlton-Robb et al., 2011) and genetics (Natoli et al. 2004, Särnblad et al. 2011, Charlton-Robb et al. 2011, Amaral et al. 2016) indicate that the taxonomic status for a number of populations in different regions should be re-evaluated.
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)
Does the assessment cover a marine EEZ area(s)?
Not_assigned
Conservation Status
Qualifying criteria (if given)
A2bc
Criteria system used
IUCN
(see Assessment details)
Assessment rationale/justification
Preen (2004) reported a 71% decline in small species of dolphins in the Arabian Gulf from 1986 to 1999, which included this species. There is no information available on decline rates in the individual species, so based on the assumption that they all declined equally it appears reasonable to infer a population reduction of >50% for Tursiops aduncus over the past three generations (63 years). Even accounting for animals off the east coast, the species, therefore, qualifies for assessment as Endangered (EN) under criterion A2bc. The reduction was due to a combination of pressures including declining habitat quality because of increasing coastal development, bycatch, collision with boats and declines in fish stocks. The decline is continuing but it is not possible to say if it is at the same rate. There is unlikely to be a significant rescue effect as it is considered likely that the population across the whole of the Gulf area has declined.
Assessment details
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.
URL (link) of redlist assessment or publication
https://www.moccae.gov.ae/assets/download/b352eff1/UNRL%20of%20Mammals%20-%20Report%202019.pdf.aspx?view=true
Further information
Endemism (according to assessment)
Endemic to region
Not assigned
Taxon distribution as listed in assessment
In UAE waters, this species occurs in both the Arabian Gulf and the Gulf of Oman. The Indo-Pacific Bottlenose Dolphin (as well as the Indo-Pacific Humpback Dolphin) is the species most likely to be seen close to shore in Abu Dhabi and Dubai (Baldwin 2005). Globally, this species has a discontinuous distribution in the warm temperate to tropical Indo-Pacific, from South Africa in the west, as far east as the Solomon Islands and the southern half of Japan and southeast Australia (Hammond et al. 2012c).
Is there a map available in assessment?
Yes
Habitat and systems
Ecological system type
Habitat
Habitat details as listed in assessment
Typically, 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. Indo-Pacific Bottlenose Dolphins have been observed feeding over sand, seagrass and reefs in the Arabian Gulf (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). Inshore and shallow-water species are further potentially threatened by entanglement in abandoned fishing gear, coastal development including port and harbour construction, dredging, land reclamation, residential and tourist development, and pollution (especially hydrocarbons). During surveys by EAD, a large number of dolphins were observed with scars that were attributed to propeller cuts, indicating that vessel strike is a major threat to dolphin populations in Abu Dhabi waters (EAD 2015). A UAE Fisheries Resource Assessment Survey in 2002 found that fish stocks in the Gulf had declined by 60%. 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 Endangered under the same criterion as the current assessment. 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, however, it appears he was not aware of the 71% decline in the species from 1986 to 1999 as reported by Preen (2004).
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
