Species: Delphinus delphis – Short-beaked Common Dolphin
There have been some exciting new findings this year, one of which is, the identification of seasonal residents. There have been some dolphin groups we have only documented once, and other groups that continue to make an appearance within the marine park. Some of these resident groups continue to engage our vessel and supply us with a host of behavioral data. Others contribute to the data, yet they are not seen again. D. delphis, is beginning to reveal similar themes found within the bottlenose populations, yet further study is necessary. The main difference appears to be that the common dolphins maintain more of an “open pod” structure, whereas most of the bottlenose groups interact within the confines of “closed pods”. The members of open pods tend to move about within the social networks of dolphins. Even with these more open pods, we do tend to observe specific individuals that are usually always seen together.
Another exciting find is the male dolphins seem to utilize male pair bonds, and male alliances. Again, this is a common theme found within bottlenose dolphin social structures yet it has not been fully documented within the social structures of D. delphis. It has been our observation that sub-adult and young males, begin leaving the safety of their maternal pod to slowly introduce themselves to the mature male groups. We have witnessed these interactions on many occasions. We first identify the young males, and document their usual sightings with mum. Over time, we observe the younger animals interacting within the adult male pods, then returning to their maternal pod. Based on the proximity of mum, in relation to the adult male dolphins, we believe they are establishing a presence, and are being accepted within the sexually-mature male pods. There is an obvious pecking order as the younger males begin these transitions, which we continue to document. Also observed is a remarkable tactile communication, confirming not only a recognition, but also an acceptance toward the young members.
Dolphin behavior has been studied for many years, yet behavior surrounding a dolphin swim vessel of this nature has never been documented before. We are gathering data to more fully understand the natural behavior of the common dolphins, and the behavior in relation to this novel swim. We are finding that behavioral states play a large role in the success of this type of swim, but the behavioral state is not the only factor. Both gender and group composition appear to be equally important. Some of the most interactive swims appear to be connected with the presence of mature male dolphins. Again, we will be able to clarify this more fully over time.
With continued interaction, a clearer picture is unfolding. We are learning things about this species that we never knew before. We are learning more about their social structure and the way they utilize this particular habitat. We are seeing the similarities, and the differences, between previously documented dolphin species, such as bottlenose. It is our hope that we will shed new light on the common dolphins of Port Stephens, and help to protect and preserve this beautiful species.
Photo Identification Shots:
Each dolphin has a distinct dorsal fin, (the fin on top of the animal’s back) which is as unique as the human fingerprint. By taking high quality images of the dorsal fin, we are able to document, and identify individual dolphins. The fins vary in a variety of ways. they vary in color or pigmentation, as well as size and shape. One of the easiest way to identify a dorsal fin is by the damage they can sustain, as seen in the dolphin Batman.
Have a look at a few of the different individual fins, and observe the many different features which make them unique.