An exciting discovery in recent years on the Kimberley coast has been the identification of the Australian snubfin dolphin (Orcaella heinsohni) as a new species to science.
Worldwide, this unconventional-looking dolphin with a melon shaped head and smiley mouth, only occurs in shallow waters of northern Australia and possibly southern New Guinea. Roebuck Bay, on the doorstep of Broome, is one of a few places known to be frequented by these typically shy animals, with pods of ‘snubbies’ often seen in the bay’s busy deep water channel and creek mouths.
To understand more about the status and ecology of nearshore dolphins, researcher Alex Brown from Murdoch University’s Cetacean Research Unit commenced a PhD in 2012.
A recent invite to join Alex and his enthusiastic research assistants on Roebuck Bay, was the perfect opportunity to find out what Alex has learnt about ‘stubbies’ over the last three years. The team is in high spirits, having just completed a successful month of surveys with help from local Yawuru traditional owners.
“During the surveys, photos of individuals are taken and identified by unique marks on their dorsal fins. We then use a mathematical model to estimate how many dolphins are using that area of the bay over a certain period of time,” Project Manager, Kandy Curran said.
In a recent report to WWF-Australia, Alex documented the exciting finding that Roebuck Bay has the largest known population of Australian snubfin dolphins recorded to date. Despite this relative magnitude, Alex is keen to point out that it is still a small and vulnerable population by conservation standards.
The target for the day on Roebuck Bay is to gather more information on the genetics of snubbies, surveying known favoured locations and collecting biopsies of tissue with a specialised dart gun.
Over the morning, more than forty snubbies are sighted feeding and socialising just a few kilometres off the town. Alex is in luck, with five new dolphins biopsy sampled. These biopsies will help determine the level of gene flow (mixing) between the dolphin populations of Roebuck Bay and Cygnet Bay.
With dolphins being good swimmers, and Cygnet Bay no more than 250 km away, you might expect animals to often move between the two areas. However, as Alex explains, this appears not to be the case.
“Preliminary data from over 50 tissue samples collected by fellow researchers Dr Deb Thiele, Simon Allen and myself show that there is limited gene flow between the two populations,” Alex Brown said. Such isolation suggests that they should be managed as separate populations.
To share the exciting research findings, Alex recently gave a captivating presentation with amazing photos and video footage to an audience of more than 70 people at the Broome Public Library. This talk was one of the monthly presentations by researchers in the Science on the Broome Coast series being run by the Roebuck Bay Working Group and Yawuru Land and Sea Unit, and sponsored by Inspiring Australia and Rangelands NRM.
For more information, contact Kandy Curran, Roebuck Bay Working Group Project Manager
Image: The Australian snubfin dolphin was only recognised as a distinct species to its southeast Asian relative ‘ the Irrawaddy river dolphin, in 2005. Photo: ©Kandy Curran, (Image 5351)