FEATURE CREATURE
FEATURE CREATURE INDO-PACIFIC BOTTLENOSE DOLPHIN (TURSIOPS ADUNCUS ) FEATURE IUCN RED LIST 2019 PHOTOGRAPHY ADA NATOLI – UAE DOLPHIN PROJECT
RED LIST CATEGORY & CRITERIA: NEAR THREATENED Scientific Name: Tursiops aduncus Synonym(s): Delphinus aduncus (Ehrenberg, 1833) Common Names: Indo-Pacific Bottlenose Dolphin, Indian Ocean Bottlenose Dolphin TAXONOMIC The Indo-Pacific Bottlenose Dolphin (Tursiops aduncus) has been recognised 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, colouration 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 recognised as a subspecies. 34
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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.
al. 2008). Furthermore, survey data suggest that Indo-Pacific Bottlenose Dolphins occur in relatively small populations or communities with limited geographic ranges, especially where they reside close to islands (Krützen et al. 2004, Natoli et al. 2008, Fury et al. 2008, Särnblad et al. 2011, Kiszka et al. 2012, Gray et al. 2018), which can exacerbate the impact of human activities and demographic stochasticity on this species.
JUSTIFICATION Indo-Pacific Bottlenose Dolphins generally occur in shallow coastal waters of the Indian Ocean, Southeast Asia and Australia. They are among the more commonly studied cetaceans in the Indian Ocean, especially in Shark Bay, Western Australia. However, information on distribution, population size, and trends in abundance and mortality from much of the species’ range is still very limited. As they are primarily coastal, Indo-Pacific Bottlenose Dolphins often co-occur with fisheries, and bycatch is a major cause of concern for this species. Indo-Pacific Bottlenose Dolphins are also at risk from high levels of noise and chemical pollution, industrial activity such as oil and gas development, and habitat reduction caused by land reclamation and coastal development (Curry and Smith 1997, Wells and Scott 1999, Reeves et al. 2003, Kiszka et
Estimates of abundance from populations for which information on bycatch is also available indicate that human-caused mortality is frequently unsustainable (Cockcroft et al. 1992, Shirakihara and Shirakihara 2012, Preen 2004). Based on the sum of existing abundance estimates, the total population size for the species over its entire range is likely well in excess of 40,000 individuals. Large parts of the range have never been surveyed (e.g. much of the Arabian Sea, Arabian/Persian Gulf, Pakistan, India, Red Sea, Somalia, Yemen, Mozambique, Indonesia, Philippines). The Indo-Pacific Bottlenose Dolphin was classified as Data Deficient in 2008. The species distribution overlaps the range of several other coastal cetacean species that are red-listed as Endangered (Irrawaddy Dolphin Orcaella brevirostris and Indian Ocean
