The sight of Ragged Fin with her new calf being flanked by Esther (above) was a great way to begin the trials of new survey techniques developed as part of the three year Dolphin Health project. (Photo: David Donnelly, DRI).
We think this is Ragged Fin’s first calf. Seeing Esther so close makes sense because we know she has had at least three calves of her own and experienced mothers are known to take on a “matriarchal” role.
Surveys in Port Phillip and Western Port have found both bottlenose and common dolphins with new calves, but most importantly, we are collecting thousands more images for us to monitor the populations.
Skin health is the only indicator of dolphin health that can be gained without invasive measures such as biopsy or capture, requiring only quality images that show the dolphin’s flank. These can be obtained by researchers with a permit to approach closely, or by “citizen scientists” on commercial vessels or private vessels that regularly have dolphins bow-ride during their normal activities.
It’s normal for dolphins to get various lesions on their skin throughout their lives and these heal surprisingly quickly in healthy animals. Persistent or worsening skin lesions can indicate that dolphins are under stress and enable action to be taken before we start seeing animals wash up on beaches.
A major part of the Dolphin Health Project is the historical analysis of our photos dating back to 1993 which will enable us to understand what is “normal” for our population and give a context to pick up changes into the future.
So far over 11,000 of the film images from 1993 to 1998 have been scanned using the new (high-resolution) scanner with individual ID’s and lesions logged. Nearly 20,000 images from 1999 to 2006 will be analysed in the months ahead. The analysis of the digital images taken from 2007 to 2015 is occurring in parallel with 8,000 images processed and 16,000 remaining.
The outcome will give us a model of the skin condition of our Port Phillip dolphins over nearly a quarter of a century to help us understand what is “normal” in terms of the type, extent and progression of lesions over this time. This will give us a reference and tool to evaluate the condition of these animals (and possibly other populations) into the future.
This work is conducted under a research permit from the Department of Environment, Land, Water and Planning. It is part of the National Whale and Dolphin Protection Plan and funded under the Australian Government’s National Landcare Programme.
May, 2015
