The Dolphins of Darwin Harbour
July 2008. Carol Palmer, a Biodiversity Conservation Scientist who works for Australia's Department of Natural Resources, Environment and The Arts (NRETA), has been uncovering the secret lives of Darwin Harbour's dolphins. Humpback dolphin and calf. courtesy of Carol Palmer, NRETA
Darwin Harbour
Darwin Harbour covers some 450 square kilometres and includes some of Australia's finest mangroves (now protected). It was first discovered by westerners in 1839 by HMS Beagle and named after Charles Darwin, although he was not sailing with the Beagle on that trip.
Ms Palmer, who embarked on the Coastal Dolphin Research project in Darwin Harbour in March 2008, says the research will allow scientists to identify key habitat areas and give an understanding of populations, and potential threats and ensure the long term conservation of these species.
Three species of coastal dolphins
"There are three small coastal dolphins living in Darwin Harbour - the Australian snubfin (Orcaella heinsohni), the Indo-Pacific humpback (Sousa chinensis) and the Indo-Pacific bottlenose (Tursiops aduncus)," Ms Palmer said.
"We also have the False-killer whale (Pseudorca crassidens) visiting the harbour, which despite its name is actually a dolphin but much larger than the small coastal dolphins.
Endemic species
"Recent genetic work identified the Australian snubfin as Australia's only endemic dolphin, but with ongoing genetic research we hope to confirm that the Indo-Pacific humpback is also endemic to Australia, which would mean it's another new Australian dolphin species and the Northern Territory has globally important populations of both dolphin species.
"The Indo-Pacific bottlenose has similar distribution but doesn't like being in shallow muddy waters whereas the other two dolphins do.
Transient and resident populations
"We've also uncovered that while there are transient dolphins in Darwin Harbour, that come and go, we actually have resident dolphin populations that give birth and raise their young in the harbour and Shoal Bay area. It's likely they live their entire lives in these areas and they can live as long as 30 to 40 years.
"Throughout the study we've managed to pick up movements of the same individual dolphins between East Arm in Darwin Harbour and Shoal Bay, so we know these areas are very important for all three species of dolphins as birthing, nursery areas and feeding grounds."
Bottlenose - common, Humpback - unusual, Snubfin - rare
Ms Palmer said that the Indo-Pacific bottlenose dolphins are fairly common, while the Indo-Pacific Humpbacks are quite rare, but the most elusive and rare is the Australian snubfin which occurs in low numbers and is proving to be very hard to find.
"All three species are found in shallow coastal waters, but the Indo-Pacific Humpback dolphin and the Australian snubfin are found closer to land and river mouths in Australia's northern waters.
The research project will run for the next two to three years here in Darwin Harbour and Shoal Bay, as well as at Garig Gunak Barlu National Park, located 570km northeast of Darwin on the Cobourg Peninsula.
Coastal and river dolphins are among the most threatened mammals worldwide.
The research project is a joint partnership between the Northern Territory Government WWF-Australia's Flagship Species Program, ING Direct and Charles Darwin University.
For more information on the project go to www.nt.gov.au/marine
