Name(s): Australian snubfin dolphin (Orcaella heinsohni)
Group: Marine mammals
Size: Length 2-2.5 metres, weight up to 130kg
Diet: Carnivore, eating fish and cephalopods (squid)
Habitat/range: Tropical coastal waters of Northern Australia including WA, NT and QLD
Conservation status: Listed as vulnerable in Queensland
Superpower: Snubfin dolphins have vertebrae that make them able to flex their necks, unlike most other dolphins and whales. Because of this, they can surface and take a breath without showing their dorsal fin – very sneaky! This means scientists must be patient when trying to photograph their dorsal fins to identify individuals and track them over time.
The snubfin dolphin lives in tropical waters of northern Australia and was only recently recognised as a species, in 2005. It was previously thought to be the Irrawaddy dolphin, a close relative that lives in Asian waters. There are currently thought to be less than 10,000 adults of the species. The highest-density population, consisting of about 100 individuals, inhabits Yawuru sea country in Roebuck Bay, Broome, Western Australia.
These dolphins have a distinctive appearance, with a blunt, round head and no beak, which makes them peculiar compared to the more familiar dolphin species. The snubfin dolphin has a small circular fin on its back, and they often sport marks on these fins from interactions with other dolphins, sharks that try to eat them, entanglement in fishing gear, and being struck by boats. The marks are handy to scientists, who use them as natural tags to tell individuals apart and track the dolphins over time through repeated photographs and sightings.
Snubfin dolphins’ favourite food is fish of varying sizes, from large salmon to small baitfish, and they can often be found feeding in creek mouths on a high tide. They have been observed displaying a specialised tactic of “spit feeding”, where they squirt a jet of water up to two metres high ahead of themselves, and seemingly startle fish back towards their mouths for an easy snack.
These dolphins are brown in colour, with a low surfacing profile – as such, they are very camouflaged in the shallow, muddy waters that they prefer. They can be very entertaining to watch as they feed in shallow waters. They perform yoga-like movements, such as head stands with their tail flukes out, while rummaging around the sea floor for fish that are hiding in the mud. Snubfins sometimes emerge from a feed covered head to fluke in muddy clay. Scientists call this behaviour “bottom grubbing”. A group of dolphins resting on the water’s surface, lined up like sausages on a barbeque, is referred to using the very Aussie term “snagging”.
A little shy around boats, snubfins prefer to swim in their mangrove habitat. They only have one young at a time, and a calf stays with its mother suckling milk and swimming close by the mother’s tail in “baby position”. After a couple of years, the calves are weaned and become independent.
This species is gregarious and can form large groups of up to 20-30 individuals with lots of close body contact when socialising. They can become very active, splashing at the water’s surface. To avoid amorous attention, you may see an inversion, where the dolphin turns up a flushed pink belly to avoid mating attempts.
Snubfins can sometimes be seen swimming with other dolphin species, such as bottlenose and humpback dolphins, socialising or feeding together. Sometimes these interactions appear amicable and may have mutual benefit; at other times they seem hostile. There is genetic evidence that snubfins have indeed mated and hybridised with humpback dolphins.
This marvellous marine species is a worthy candidate for Australian Mammal of the Year!
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Originally published by Cosmos as Australian snubfin dolphin: a dolphin that does ‘yoga’
Dr Holly Raudino is a Senior Research Scientist in the Marine Science Program of the Department of Biodiversity, Conservation and Attractions. Holly’s work focuses on the population biology and behaviour of marine mammals. As a conservationist, she is most passionate about protecting threatened species and applied research that informs management of the marine environment.
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