The Australian snubfin dolphin (Orcaella heinsohni ) is a dolphin found off the northern coasts of Australia. It closely resembles the Irrawaddy dolphin (of the same genus, Orcaella ) and was not described as a separate species until 2005. The closest relative to the genus Orcaella is the killer whale, Orcinus orca. The Australian snubfin has three colors on its skin, while the Irrawaddy dolphin only has two. The skull and the fins also show minor differences between the two species.
This strange looking but very cute dolphin was not recognized as being a new species until 2005. People previously thought it was the Irrawaddy dolphin, but DNA skull measurements and DNA profiles by Californian and Queensland scientists show that the Australian snubfin, with its round melon-like head and short stubby dorsal fin, is a distinct species. This dolphin’s color varies from dark brown to creamy colored and all shades in between. They have a rounded forehead and no beak, unlike most of Australia’s other dolphin species. Their dorsal fin is particularly small (which gives them their common name) and there is a distinct and quite mobile crease around the neck. Their blowhole is set slightly to the left.
Australian snubfin dolphins are natives of Australian and the Oriental coastal waters around the Sahul shelf. They occur as far northwards as Manokwari, Indonesia and as far to the south as Australia’s Brisbane River. Within Australia their range is from Brisbane in Queensland to Broome in Western Australia. These dolphins live in coastal waters of up to 30 m deep and as far as 23 km from the coast. Groups of them are often found near river and creek mouths. They prefer shallow areas of seagrass rather than dredged channels, and they also like areas with coral reefs.
Australian snubfin dolphins occur in groups of up to six, though sometimes as many as 15. When undisturbed, typically they make short dives, coming to the surface quietly every 30-60 seconds. They are able to stay underwater for as long as 12 minutes when disturbed. It is a very shy animal that keeps away from boats. Although not regarded as acrobatic dolphins, partial jumps and tail-slapping have been observed. They produce broadband clicks, two different kinds of whistles and three different kinds of pulsed sound to communicate with each other. During foraging they will produce clicking sounds and during social behavior they often produce squeaking sounds.
Australian snubfin dolphins eat anchovies, sardines, eels, breams, halibut and grunters. Cuttlefish, squid, and other cephalopods are important in their diet also, and they occasionally eat isopods and decapod crustaceans.
Reproduction is under researched for this species. It is thought that they are monogamous (with one male mating with one female exclusively), based on the strong, stable associations within groups. Mating seems to mainly take place from December to April, which is the wet season. The gestation period is about 14 months and usually one offspring is born, with a birth mass of 10 to 12 kg. As these animals have a tight social structure, the young are probably reared communally. Australian snubfin dolphins are able to swim at birth. At about the age of two they are weaned, and they stay close to their mother with their natal group until reaching adult size, between the ages of 4 and 6. It is believed that at this time, the dolphins leave the social group of their mother.
The major threats for Australian snubfin dolphins include the following: entanglement in gill nets in shallow waters set for fishing and in shark nets that are set to protect humans, and habitat degradation (pollution, coastal zone development, boat traffic, and overfishing of the dolphin’s prey resources).
According to the IUCN Red List resource, the number of mature animals is well under 10,000. Specific population are estimated for the following areas: about 1,000 animals (the highest estimate was 1,227 animals) in the Gulf of Carpentaria, Northern Territory, Australia; 62-78 animals in Cleveland Bay, Queensland; 15 groups totaling 88 individuals along parts of the northeastern Kimberly Coast. According to the Wikipedia resource, about 200 individuals were found in the Pacific Ocean off Townsville. Overall, currently Australian snubfin dolphins are classified as Near Threatened (NT) on the IUCN Red List.
Australian snubfin dolphins are major predators of fish and cephalopods in the coastal regions of Australia and Indonesia.
