The Burrunan dolphin (Tursiops australis) is a proposed 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, but other phylogenetic studies using different methodologies indicate that it is a subspecies of the Indo-Pacific bottlenose dolphin. 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.
Burrunan dolphins are dark bluish-gray at the top near 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, Burrunan dolphins are smaller than Common bottlenose dolphins but larger than Indo-Pacific bottlenose dolphins.
There are two resident populations of the Burrunan dolphin; one in Port Phillip and the other in the Gippsland Lakes. Burrunan dolphins usually occur in coastal waters, sheltered bays, and estuaries.
Very little information is available regarding the behavior of Burrunan dolphins. They are known to spend time in small pods consisting of up to 10 individuals; however, larger aggregations have also been observed. Burrunan dolphins use various feeding techniques to capture their prey, including cooperative hunting. They may also hunt singly. They search for food using echolocation; the dolphin locates objects by producing sounds and listening for the echoes. A broadband burst pulse of clicking sounds is emitted in a focused beam in front of the dolphin. When the clicking sounds hit an object in the water, like a fish or rock, they bounce off and come back to the dolphin as echoes. Echolocation tells the dolphins the shape, size, speed, distance, and location of the object.
Burrunan dolphins are carnivores (pisciovores). They feed on small fish and cephalopods such as squid and cuttlefish.
Burrunan dolphins can breed at any time throughout the year but peaks usually occur during spring and summer. After the gestation period of approximately 12 months, females give birth to a single calf. The young can swim and breathe at the water’s surface right after birth. Females nurse their calves for about 12-18 months and they may stay with their mothers for several years before becoming independent. Young females become reproductively between 5 and 13 years of age, while males start to breed when they are between 7 and 15 years old. Brrunan dolphins usually give birth every 2 to 3 years.
Burrunan dolphins are 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. Burrunan dolphins are 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 localized 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.
According to the Wikipedia resource, the total population size of the Burrunan dolphins is less than 180 individuals. The combined population has been estimated as about 100 individuals in Port Phillip and 50 individuals in Gippsland. According to the State Government of Victoria resource, the population size of the Burrunan dolphin in Port Phillip Bay is approximately 120 individuals, and the other in the Gippsland Lakes - approximately 63 individuals. Presently, the Burrunan dolphin is not included in the IUCN Red List and its conservation status has not been evaluated.