The Burrunan dolphin (Tursiops aduncus australis ) is a subspecies or potential species of bottlenose dolphin found in parts of Victoria, Australia first described in 2011. Its exact taxonomy is debated: numerous studies support it as being a separate species within the genus Tursiops and occupying a basal position within the genus, but other phylogenetic studies using different methodologies indicate that it is a subspecies of the Indo-Pacific bottlenose dolphin (Tursiops aduncus ). The Burrunan dolphin is not currently recognized as a species by the Society for Marine Mammalogy or American Society of Mammalogists, which cites problematic methodology in the original study proposing species status and recommends further research.Show More
There are only two known resident populations in Victoria, Australia, with an estimated total population size of less than 180 individuals, and the predicted effective populations sizes small; Port Phillip Bay: 81.5, Gippsland Lakes and Tasmania: 65.5.
Prior to proposal of the name T. (aduncus) australis, the term "Tursiops species, southern Australian bottlenose dolphin (SABD)" had been used.Show Less
The Burrunan dolphin is dark bluish-gray at the top near to the dorsal fin extending over the head and sides of the body. Along the midline, it is a lighter gray which extends as a blaze over on the side near the dorsal fin. Ventrally, it is off-white, which reaches over the eye and the flipper in some instances. By size, it is smaller than the common bottlenose dolphin, but larger than the Indo-Pacific bottlenose dolphin, measuring between 2.27 and 2.78 m (7.4 and 9.1 ft) in length.
The recognition of T. aduncus australis is particularly significant given the endemism of this new subspecies to a small geographic region of southern and south-eastern Australia. Only two resident populations of the Burrunan dolphin have been identified, one in Port Phillip and the other in the Gippsland Lakes. Their combined population has been estimated as about 100 in Port Phillip and 50 in Gippsland. Additionally, T. australis haplotypes have been documented in dolphins located in waters off eastern Tasmania, and in coastal waters of South Australia in the Spencer Gulf region and west to St Francis Island. The initial report on the Burrunan dolphin suggested that the low number of individuals found might immediately qualify the population for protection under the Environment Protection and Biodiversity Conservation Act. The Burrunan dolphin is yet to be listed, or categorized, under the EPBC Act or IUCN Red List due to data deficiencies; however, it is listed as ‘Endangered’ under the State of Victoria’s Flora and Fauna Guarantee Act 1988.
The subspecies is found in estuaries and sheltered bays of the southern coasts of Australia, often in locations that make them vulnerable to human activities. Anthropogenic disturbances, such as dolphin-swim tour vessels, distract Burrunan dolphins from foraging and resting. The Burrunan is vulnerable to extinction due to several different factors relating to exposure to threats, data deficiency, low genetic diversity and low population sizes, high mercury levels, and increased risk from pathogens and contaminants. Small localised populations may be at high risk of extinction through demographic and genetic stochasticity, particularly if they occur close to urban areas where anthropogenic threats abound. Anthropogenic activities, such as cetacean-based tourism or recreational boating, can impact dolphins through physical presence, non-compliance to regulations and acoustic disturbance. Such disturbances can negatively affect the long-term viability of small resident populations, summarised in Puszka et al. 2021.Show More
As recent case study conducted by the Marine Mammal Foundation and RMIT (Research Lead Dr Kate Robb), provided the first field assessment of vessel compliance with the Wildlife (Marine Mammal) Regulations 2009 in Gippsland Lakes, Australia, and provide the first assessment of the endangered Gippsland Lakes Burrunan dolphin (Tursiops australis ) population’s behavioural ecology. Dolphin behaviour and vessel regulation compliance data were collected during boat-based surveys of Gippsland Lakes from July 2017 to January 2018, with a total of 22 dolphin group sightings resulting in 477 five-minute point samples. 77% of dolphin sightings involved vessel interactions (within 400 m), and 56 regulation breaches were observed. These breaches were most severe in summer (mean = 4.54 breaches/hour). Vessels were found to alter dolphin behaviour before, during, and after interactions and regulation breaches, including increased mating (mate guarding) and milling behavioural states, and increased ‘fish catch’, ‘high leap’ and ‘tail slap’ behavioural events. These behavioural changes may indicate masking of the dolphins' acoustic communication, disturbance of prey, increased dolphin transition behaviours, and/or induced stress and changes to group structure (including increased mate guarding).
Fresh water skin disease (FWSD) has been described from the population in Gippsland Lakes, when weather conditions caused excessive influx of fresh water into the normally brackish-to-salty lake system. Increased incidence of these weather events could threaten the small population in the lakes.Show Less