Australian snubfin dolphin
Common name: Australian snubfin dolphin
Scientific name: Orcaella heinsohni
Legislative name: Orcaella brevirostris
Family: Delphinidae (dolphins)
The Australian snubfin dolphin is listed as Vulnerable Queensland (Nature Conservation Act 1992). It is only known from Australasia and its distribution and abundance in remote areas of Queensland remains uncertain. Local populations are considered to be vulnerable to decline because of small population sizes and low population growth rates.
The Australian snubfin dolphin was assumed to be the Irrawaddy River dolphin (Orcaella brevirostris) until 2005 when it was described as a separate species. Adults average 2 metres in length (maximum male - 2.7 m, maximum female - 2.3 m). The species is easily recognised from other dolphins from its blunt, rounded head and absence of a beak. The only species it could be confused with is the dugong, which lack a dorsal fin and have a more robust shape. The dorsal fin in snubfin dolphins is small compared to other dolphins, with a tip that is blunt and rounded. The colour is generally pale to dark brown with the ventral (underside) surface lighter in colour. It has an obvious, flexible, neck, and neck creases may be present. The flukes (tail fins) are notched and have a shallow concave trailing edge and the flippers are large and broad, with a gently curved leading edge. There are 12-19 small, conical teeth on each side of both jaws. The blowhole is left of the midline. A hybrid between the Australian snubfin dolphin and the Australian humpback dolphin (Sousa sahulensis) was recently discovered in Western Australia, but hybrids are considered to be rare.
Habitat and distribution
The Australian snubfin dolphin has been recorded across northern Australia (Qld, NT, WA) where it inhabits riverine, estuarine and coastal waters. The most southerly resident population in Queensland occurs in Port Alma/Keppel Bay near Rockhampton. Sightings to the south of Port Alma are rare. A snubfin dolphin stranded dead in the upper Brisbane River in 1998 but this was considered to be a vagrant. Other known populations occur off Bathurst Head and in Princess Charlotte Bay, Cleveland-Halifax Bay and Repulse Bay. The distribution of Australian snubfin dolphins is poorly known in the Gulf of Carpentaria and the Cape York Peninsula, but they have been reported in Port Musgrave and in waters off Weipa. Australian snubfin dolphins are often seen in the same areas as Australian humpback dolphins, although they are often closer to estuaries and river mouths than humpback dolphins.
Life history and behaviour
The Australian snubfin dolphin is usually seen in groups of 5 to 6 animals, but groups of up to 15 animals have been observed. When undisturbed they typically make short dives, surfacing quietly at 30-60 second intervals. They can submerge for up to 12 minutes when disturbed. Tail-slapping and partial jumps have been observed, but they do not leap clear of the water or bow-ride. Australian snubfin dolphins communicate with sounds that include broadband clicks, pulsed sounds and whistles.
The Australian snubfin dolphin is a generalist feeder, taking food from the bottom of the ocean and the water column. Its diet consists primarily of fish, but includes cephalopods (such as squid and octopus) and crustaceans (such as prawns and crabs). They are sometimes observed to squirt water from their mouth, a behaviour that is thought to be linked to foraging.
Threats to the Australian snubfin dolphin include habitat loss and degradation, noise pollution, poor water quality, boating activities, incidental capture in fisheries and incidental capture by the Shark Control Program. Entanglement and ingestion of recreational fishing gear (hooks and line) or marine debris may also pose a threat. Snubfin dolphins are exposed to pollution that is amplified up the food chain, and may cause them to be more susceptible to disease.
- Implement sustainable fisheries management to minimise accidental capture in fishing gear;
- Improve water quality on the Great Barrier Reef through the Reef Water Quality Protection Plan
- Provide education on the impacts of boating activities on the dolphin.
- Promote fishing practices that reduce interactions with wild dolphins.
- Protect significant Australian snubfin dolphin habitat through marine parks.
- Undertake ongoing research and monitoring to determine more about the species' life history parameters, distribution, movement patterns and population sizes.
- Monitor dolphin mortality along the Queensland coast via StrandNet, the marine wildlife stranding and mortality database.
What can you do to help this species?
- Report injured, sick, entangled, stranded or dead dolphins to the RSPCA hotline on 1300 ANIMAL (1300 264 625).
- Do not approach dolphins too closely with your boat as Australian snubfin dolphins are sensitive to harassment and unfamiliar noise, and boats may disturb their natural behaviour.
- Avoid fishing near dolphins that are feeding—they may mistake your bait for food; avoid feeding dolphins with leftover bait and use corrodible hooks.
- Remember that rubbish you throw away, or chemicals you discard, may find their way into drainage systems that run into the ocean. Such pollutants can affect the health of coastal mammals directly, or indirectly through accumulation of poisonous substances in their prey.
- Do not feed wild snubfin dolphins. Unregulated feeding of wild dolphins can introduce disease and cause behavioural changes (such as dolphins learning to approach fishers or boats).
- Do not dump your pet cat's waste into drains. Cat faeces can contain the parasite Toxoplasmosis gondii which has caused the death of inshore dolphins.
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Beasley, I, Robertson, KM and Arnold, P 2005, Description of a new dolphin, the Australian snubfin dolphin Orcaella heinsohni sp. n. (Cetacea, Delphinidae), Marine Mammal Science 21 (3), 365-400.
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