People and Places
Our common dolphins may be globally unique
by Mornington Peninsula Magazine

Dolphin Research Institute

Did you know that the waters near Mornington are home to a globally significant community of animals? It seems a group of oceanic common dolphins came into Port Phillip from the open ocean about 2005 and are now permanent residents. To the best of our knowledge, these species live in the open ocean everywhere else in the world except in our remarkable bay. 

The Dolphin Research Institute’s research team first encountered this small group of common dolphins feeding near Mornington in 2005. At first we thought it was a chance encounter with a vagrant group of animals, but as time moved on, sightings became more regular until it was realised that these dolphins had made Port Phillip their home. Sixteen years later and that small group of a dozen or so individuals has grown to a community of about 40. Through the analysis of thousands of images we can now say that not only have known females in the community had multiple calves in the bay, but these calves also appear to be surviving and are beginning to form small sub-groups of their own.  This truly is a good news story for our dolphins and the bay itself, especially when you consider the concerning trends for coastal dolphin communities in Australia and globally. 

Common dolphins can be distinguished from the bay’s other resident dolphin species, the bottlenose dolphin, by their much smaller size – about 2m – and striking tri-colouration hourglass flank patterning of brown, grey and light tan.

The DRI has monitored this community of dolphins since they were discovered, using land and vessel-based surveys. Through these efforts we have confirmed that many of the animals photographed on that day back in 2005 are still with us, thriving in our local waters. These surveys have also led to an understanding of social and age groupings, skin health, calving rates and overall numbers.  This information provides an indication of the health of the dolphins which is shared with government agencies to support environmental management decisions.  This long-term and ongoing monitoring is crucial in supporting the protection of our dolphins and their environment.

The winter months are best for viewing the common dolphins from land because they tend to venture closer to the coast at this time, presumably in pursuit of prey. Head for an elevated vantage point, use binoculars, and look for diving birds.

The DRI would like to acknowledge the valuable contributions made by our local supporters, Bay Fish N Trips and the wonderful community of citizen scientists who report their sightings. Without these contributions we would certainly not know as much as we now do about these amazing animals.

There are three important things that we can all do to help protect our special dolphins:

• Commit to the DRI’s Dolphin Distancing campaign. This is a positive and long-term campaign to normalise doing the right thing in your vessel around dolphins;

• Report your dolphin and whale sightings through the PodWatch app on the DRI’s website; and,

• Support the institute’s work by becoming an Adopt-A-Dolphin member. You can actually choose one of four common dolphins.   

You can find out more about our dolphins and how to become involved at

DAVID DONNELLY, research officer at the Dolphin Research Institute

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