New species of bottlenose dolphin described

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Scientists have described a new species of bottlenose dolphin that makes its home within sight of one of Australia's largest cities, making it only one of three dolphin species described since the 1800s.

Kate Charlton-Robb and colleagues name the new species, which is endemic to the coastal waters of south and southeastern Australia, the Burrunan dolphin (Tursiops australis) in a recent issue of the online journal PLoS ONE. 

The common name comes from the aboriginal word meaning "large sea fish of the porpoise kind", while its species name is Latin for southern and refers to its links to Australia.

Previous research on the DNA of the bottlenose dolphins hinted that populations from southern Australia were genetically distinct enough from the Common bottlenose dolphin (T. truncatus) and the Indo-Pacific bottlenose dolphin (T. aduncus) to be considered a separate species. 

The discovery of two forms of bottlenose dolphin in southeastern Australia: a physically smaller coastal form in semi-enclosed water bodies, and a larger more robust offshore form, appeared to provide supporting evidence for this hypothesis.

This prompted the authors to examine dolphin skulls in the museums, where they found additional differences in cranial morphology that confirmed the existence of the new species. 

In addition to its genetic distinctiveness, the Burrunan dolphin differs from the other bottlenose dolphins in reaching a smaller size, having a more curved dorsal fin, stubbier snout, and a conspicuous tri-banded colour consisting of dark grey on top, light grey in the middle and off white below.

Although it is surprising that the Burrunan dolphin has escaped recognition for so long, this species was nearly discovered in 1915 after a scientist captured one, but erroneously believed it to be a southern form of the Common bottlenose dolphin.

Over the years, physical variation in the southern Australian bottlenose dolphins have been recognised by various workers, but this is the first such study that uses multiple lines of evidence to prove the existence of a distinct, unnamed species.

Two populations of the Burrunan dolphin are known to exist: one consisting of about 90 individuals in Port Phillip Bay near Melbourne, Australia's second most populous city. The other population of about 50 individuals is known from the saltwater coastal lakes of the Gippsland region, a little over 200 km to the east.

The species may have a wider distribution, as DNA studies have shown that it may also be present in eastern Tasmania and other parts of southern Australia.

Given the Burrunan dolphin's endemism to a small region of the world, with only two small known resident populations and the proximity of those to areas with considerable human presence, the authors advocate its listing as a threatened species for protection under Australian law in order to conserve this species.

For more information, see the paper: Charlton-Robb, K, L-a Gershwin, R Thompson, J Austin, K Owen and S McKechnie (2011) A new dolphin species, the Burrunan Dolphin Tursiops australis sp. nov., endemic to southern Australian coastal waters. PLoS ONE 6, e24047. doi:10.1371/journal.pone.0024047

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