Introducing one of Port Stephens' most popular resident dolphins - Shirley (or PS318) You may well spot Shirley on a dolphin cruise around the bay. He (yes 'Shirley' is a he) is easy recognised by his distinctive missing dorsal tip. Imagine Cruises' Lisa Skelton has watched and photographed Shirley since he was a young calf and delighted in his progression as he eventually matured enough to separate from his natal pod and establish a male alliance with 3 other males of similar age.
Between 90 to 120 individual dolphins live in Port Stephens year round. This bottlenose dolphin population is divided into two mixed-gender communities. Dolphins often form long-term social relationships with other dolphins living in the same community. These communities have different home ranges, where one community lives predominantly in the eastern section or basin of the port (from the heads to Soldiers Point) and the other lives in the western basin of the port (from Soldiers Point, west to Karuah and Big Swan Bay).
The ranges of these communities sometimes overlap, providing for social interaction between the two communities and genetic mixing. The largest community of bottlenose dolphins lives in the eastern section of the Port. This community is mainly comprised of adults, subadults and calves and occupies a small core area focusing on the marine (ocean) environment. Habitats in this area consist of sandy substrates and large seagrass beds with strong tidal influence of coastal waters.
A smaller community of generally closely-related bottlenose dolphins inhabits the western section of the Port. These western dolphins focus on riverine (river-like) environments with muddy benthic (bottom) habitats, influenced by often turbid water and freshwater outflow from local rivers.
Not only do the two communities prefer to live in different habitats, they also socialise very differently to each other. Most dolphins in the eastern community have lots of associates and change their preferred associates on a regular basis. Dolphins in the western community, on the other hand, have fewer associates, but their social bonds are much stronger. They are also much more related to each other, compared with dolphins in the eastern community.
Such differences in social behaviour between two communities have currently not been observed in any other population or animal. This makes the Port Stephens population highly unique.
Photography ©Lisa Skelton, all rights reserved.