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National Biodiversity Month – Burrunan dolphin

National Biodiversity Month – Burrunan dolphin

National Biodiversity Month is celebrated in Spring each year. Designed to highlight the diversity of life found across Australia, National Biodiversity Month also aims to promote the understanding, protection, and conservation of our natural systems.

In Victoria, we are incredibly lucky to have such a large diversity of marine mammals in our local marine environments, including twenty-five species of whales, three species of dolphin and six species of seals!

In celebration of National Biodiversity Month, we will be highlighting these amazing animals we are so lucky to have in our own watery backyards, beginning with our very own Burrunan dolphin!

Burrunan dolphin (Tursiops australis)

There has been a long association between humans and dolphins in Victorian waters, however comprehensive analysis and research of Victoria’s dolphins had not been undertaken and the species inhabiting these waters had not been determined. It was thought that the dolphins which inhabited the waters of Victoria were either the common bottlenose dolphins (Tursiops truncatus) or the Indo-Pacific bottlenose dolphin (Tursiops aduncus).

That is, until 2011, when MMF Founding Director and Head of Research Dr Kate Robb formally described, classified, and named a new dolphin species endemic to southern and south-eastern Australia, the Burrunan dolphin (Tursiops australis)!

WHAT DO WE KNOW?

The Burrunan dolphin is approximately 2.5m in length and has a distinct tri-colouration pattern, from dark grey on the upper side of the body, a paler grey midline and cream underside. The cream underside can extend over the eye, whilst the grey mid-line forms shoulder blaze (a brush-stroke pattern) below the falcate (curved) dorsal fin. The Burrunan has broad tail flukes, a prominent rounded head and a short stubby rostrum (nose). Burrunan dolphins are social animals are most commonly seen in pods of 2-30 animals.

The Marine Mammal Foundation is the only organisation in Victoria with a dedicated research program for the Burrunan dolphins….so what does our research show?

Burrunan dolphins inhabit south-eastern Australian waters, including South Australia, Victoria, and Tasmania. In Victoria, there are currently two known resident populations of Burrunan dolphins; Port Phillip Bay and the Gippsland Lakes. However, the Port Phillip Bay Burrunan dolphins and the Gippsland Lakes Burrunan dolphins are two separate populations, as there is very little migration and gene flow between them. Through MMF research, we know that there are approximately 120 resident Burrunan dolphins in Port Phillip Bay, and only 63 in the Gippsland Lakes.

Interestingly however, the Gippsland Lakes Burrunan dolphin population increases in size during the winter months. This population increase is due to the arrival of groups of male Burrunan dolphins migrating to the Gippsland Lakes from offshore and Tasmania. Each year, we see the same male dolphins migrating to the Gippsland Lakes. These individuals are well known to the MMF team, and include favourites such as Bruce, Marlin, Noel and Nemo!

Being such small populations with very low numbers, there is a severe conservation threat for our Burrunan dolphins, and as such Burrunan dolphins are listed as ‘Endangered’ under Victoria’s FFG Act. There are many threats and dangers facing our Burrunan dolphins, and unfortunately most of them are caused by humans. Plastics, litter and marine debris, along with irresponsible boating and fishing, can all have severe long-term impacts on the health of the species. However, we can all be the solution to these issues, and make positive changes to ensure our Burrunan dolphins remain an important part of our Victorian marine ecosystem.

The Victorian Government lead “Assessment of the Values of Victoria’s Marine Environment” (VEAC) list the Burrunan dolphins as a ‘Natural Value’ to the region and in numerous locations identified chemicals/heavy metals and swim tourism as a threat. The Burrunan dolphin is also recognised as vulnerable fauna within the Gippsland Lakes RAMSAR site (Gippsland Lakes Ramsar Site Management Plan), and has been listed as a High Priority value for management with Resource Condition Targets set to maintain the existing population of Burrunan dolphins due to their ecological importance and identified high risks (Gippsland Lakes Ramsar Site Management Plan).

Fun facts!

  • The Burrunan dolphin was formally described and named in 2011 by MMF’s Founding Director Dr Kate (Charlton
  • -Robb et al. 2011)
  • The Burrunan dolphin is the most ancestral node of all Tursiops (bottlenose) species (Moura et al. 2013).
  • A Burrunan dolphin calf is cared for by its mother for between 3-5 years.
  • The Burrunan are known to inhabit semi-enclosed embayments, estuarine systems, have been noted high up in freshwater rivers and along open coastal environments.
  • While all dolphins use sound to communicate (known as echolocation) Burrunan dolphins are known to make sounds and vocalisations unique to the species!

  • The Gippsland Lakes Burrunan dolphins share a close genetic connection with Burrunan dolphins from Tasmania. However, there is very little connection between our Gippsland Lakes and Port Phillip Bay Burrunan dolphins.
  • ‘Nemo’ (GL10423) pictured here got his name because he is missing part of his right pectoral fin, just like Nemo’s “special fin” from the film! From the scarring it looks like Nemo lost his fin through a white shark bite!
  • Burrunan dolphins have also been sighted interacting with other marine mammals including Australian fur seals, common dolphins, humpback whales, and southern right whales!

 

More science stuff about on the Burrunan dolphin species status from Dr Kate

Formally classified in 2011 as a new dolphin species, the Burrunan dolphin (Tursiops australis) was described using skull and external morphology in addition to numerous genetic regions(Charlton-Robb et al. 2011), consistent with recommendations of the Workshop on Cetacean Systematics (Reeves et al. 2004) and the Unified Species Concept (De Queiroz 2007).

Since the original species description (Charlton-Robb et al. 2011) there is now a larger body of genetic evidence further validating the Burrunan dolphin as a separate species. Recent assessments of Tursiops species using the mitogenome (Gray et al. 2018; Moura et al. 2013), mtDNA (Oremus et al. 2015), combined mtDNA/nuDNA (Gray et al. 2018), and more recently in the time calibrated molecular phylogeny of Certiodacyla (Zurano et al. 2019), further strengthen the phylogenetic placement in a distinct monophyletic clade, as a sister genus to all other sampled Tursiops species.

When placed in a global phylogeny within the Family Delphinidae and/or subfamily Delphininae, the Burrunan dolphin is consistently reported as divergent and sister taxa to the two both the Indo-Pacific and common bottlenose dolphins, validating the Burrunan as a separate species (Moura et al. 2013). In addition, it was found that the Burrunan stemmed from the deepest ancestral node (Gray et al. 2018, Moura et al. 2013), correlating this with geological records provides an explanation for possible divergence of 1.07 million years ago, suggesting that the origin of the Tursiops genus may be coastal habitats of Australasia (Moura et al. 2013, Charlton-Robb et al. 2015).

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