Indo-Pacific bottlenose dolphin

Tursiops aduncus
Other names: 
  • Indian Ocean bottlenose dolphin
Maximum length: 
  • Male: 2.7m
  • Female: 2.6m
  • Calf: 1.1m
Maximum weight: 
  • Male: 230 kg's
  • Female: Unknown
  • Calf: 21 kg's
Diet: 
  • Schooling, demersal and reef fish
  • Squid
  • Octopus
Estimated population: 
6,000
IUCN Listing: 
DD
CITES Appendix: 
II
CMS Appendix: 
II (Arafura/Timor Sea populations)
Classification: 

Originally, the Indo-Pacific bottlenose dolphin was grouped together with the common bottlenose dolphin and they were considered to be the same species. Now, however, it is recognised as a separate, though closely related, species. It continues to be the target of directed hunts in several locations. The complex social behaviour of the bottlenose dolphins of Shark Bay, western Australia, have been extensively studied and this population are known to exhibit a fission-fusion type of society as with other bottlenose dolphins of both Tursiops species and it also provides the only documented example of tool use by a cetacean species as some members of this population have been found to carry a sponge on their beaks to protect them from sea urchin spines when foraging in the bottom sediments.

As with many species of whale, dolphin and porpoise, taxonomic classification can be a tricky and disputed business. Recent mtDNA and microsatellite genetic evidence for example, indicates deep evolutionary divergence between small coastal dolphins endemic to south-eastern Australia and the two currently recognised Tursiops species. In 2011, scientists described this “new species” as Tursiops australis sp. nov., with the common name of ‘Burrunan Dolphin’ following Australian aboriginal narrative however to date there has been no official classification recognised by the IUCN.

Appearance: 

The Indo-pacific bottlenose dolphin is very similar to the common bottlenose dolphin. Generally it is somewhat smaller and slimmer than its common cousin, having a less robust melon and a longer, thinner beak, which contains more teeth. The dorsal fin is broad-based and falcate, proportionately taller than that of the common bottlenose dolphin. Colouration of the Indo-Pacific dolphin is also similar to the common species; it is greyish to milky brown with a noticeably darker cape and lighter belly. Some individuals have a spotted belly, but this is highly variable among individuals and is often age-dependant. The young are generally darker and more uniform with less spots. It is predictably most often confused with the common bottlenose dolphin where their range overlaps, but it is also confused with the pantropical spotted dolphin and the Indo-Pacific humpback dolphin.

Behaviour: 

Behaviour is much the same as that of common bottlenose dolphins. Indo-Pacific bottlenose dolphins are inquisitive, highly intelligent, adaptable predators, capable of problem solving, tool-use and exhibiting some flexibility in terms of prey. They are playful and can be seen leaping from the water, riding on the bows of ships and playing with fish, seaweed or marine debris. They generally form pods of 5-15 animals, though they can be found in groups of several hundred individuals. They form mixed schools with common bottlenose and Indo-Pacific humpback dolphins.

Distribution: 

The Indo-Pacific bottlenose dolphin is found in tropical and temperate waters of the Indian and western Pacific Oceans. Found almost exclusively over the continental shelf, they appear to prefer shallow, nearshore waters throughout their range. Indo-Pacific bottlenose dolphins continue to be hunted in large numbers in Japan and elsewhere, both for the captivity industry and for human consumption. Accidental mortality through fisheries bycatch is also a major problem for this species, as is chemical pollution and other forms of coastal habitat degradation. They are also disturbed by harassment from boat traffic and commercial dolphin watching, as well as live-capture for display purposes. Their IUCN Red List classification is Data Deficient worldwide. However, many inshore Indo-Pacific bottlenose dolphins exist in small, relatively isolated populations and these groups may be especially vulnerable.

Distribution map: