Dolphins have been prominent in the scientific community for their evolutionary success. Recently, Dartmouth alum Richard C. Connor observed bottlenose dolphins in Shark Bay, Australia, by examining their complex interactions. Connor noted that the dolphins’ large brains undoubtedly affected their society so he delved further by examining their large brain evolution and its similarities with that of other mammals. His article was published in the April 2007 online issue of Philosophical Transactions of the Royal Society B: Biological Sciences.
To begin with, Connor examined the social interactions between the dolphins. Similar to humans and primates, dolphins have alliances in their large community. They live in a type of society known as a “fission-fusion” society in which individuals have intimate groups, known as first-order alliances, and may change these groupings frequently. Larger gatherings of males can form looser bonds as second-order alliances. The constant interaction among the multitudes of alliances brings up the problem of third party relations where a dolphin may not know friend from foe outside their own organization. The “relationship uncertainty” among dolphins adds more complexity to their lives.
To discern between close alliances and other males, the bottlenose dolphins recognize their fellow alliance members in multiple ways. Touching of pectoral fins only occurs among members in an intimate group. Synchrony is a way to identify friendly members in the pod. Connor has observed dolphins in close alliances leap from the water simultaneously. A dolphin may “test the bond with his putative allies” through synchrony. Movement is not the only method by which dolphins can acknowledge each other.
Communication is key in large societies, such as a dolphin pod. Although there is not sufficient data to prove the following conclusion, dolphins are believed to have “signature whistles” that they may use to communicate. In many communication exchanges, dolphins have been observed to use particular sounds with specific other dolphins. All these complex interactions would not be possible without the dolphins’ large brains.
There exist three groups of mammals who independently evolved large brains: primates, elephants, and odontocetes such as sperm whales and dolphins. All three have evolved to reduce unnecessary energy loss. Dolphins, for example, have developed more muscles to allow long distance travel and more digestive tissues to efficiently digest their food. These three groups also live in large societies, reducing infant mortality due to predators, and have fewer offspring so that each one gets more attention. Without their evolved brains, dolphins probably would not have specialized into such elaborate societies.
Connor’s study sheds a lot of light on the intricate interactions and alliances among the bottlenose dolphins. Yet, as Connor succinctly states, “we should not imagine that we have stumbled…on the most complex society in the entire family.” There may exist other odontocetes that maintain even more elaborate communities.