Social life in the estuary | The Fin Review

Individuals associate in groups that change in composition and size daily, even hourly.

These groups often include both males and females although associations between the sexes are often linked strongly to the females’ reproductive state.

Most bottlenose dolphins seem to form stronger relationships between members of the same sex.

In Shark Bay, for example, adult females vary from being solitary to having a large network of affiliates.

In contrast, adult males form alliances on multiple levels, not observed elsewhere on the coast, as a consequence of high competition for access to females.

First-order male alliances are formed by pairs or trios of highly associating males.

To guard or gain access to females, these smaller groups of males form alliances with others, establishing second-order alliances.

The second-order alliances then form links with other wider groups, to establish third-order alliances.

Juvenile dolphins who are not yet constrained by mating pressures are often found to spend considerable time in large groups engaging in play to cultivate relationships and practice their social skills for the future, though sometimes they join back up with a group more similar to a ‘mother’s group’.

In the Peel-Harvey we often see adult females with their calves in groups together, and females who do not have calves often join these groups or are seen alone.

As we continue our research we hope to understand how the social organisation of dolphins in the Peel-Harvey compares to the patterns described in other populations.

The MDRP is a partnership between Murdoch University, City of Mandurah, Peel Development Commission, John and Bella Perry, Mandurah Cruises and Mandurah Dolphin Rescue that commenced in January 2016.

They are measuring how many dolphins use the Peel-Harvey waterways and how they are connected to dolphins in nearby coastal waters.

You can follow the project on Facebook or through this fortnightly column.