171 — Highly dynamic fission–fusion species can exhibit leadership when traveling

My friend Megan studies bottlenose dolphin community structure: She recommended this paper to me over coffees, which is — just so you know — the best way to show me anything.

Bottlenose dolphin pods are dubbed “fission-fusion” groups: There is a great deal of dynamic change in group composition and size as dolphins join or leave a group. One thing that remains consistent, however, is that a small number of individuals act as the group “leader,” swimming in front of the group and leading changes in direction.

Having a good leader is important because the rest of the group depends on the leader to direct them toward resources and away from danger. This is consistent with other species that travel in groups: A knowledgeable matriarch elephant can lead her herd toward water sources even when they have not visited the location in over a year.

Dolphins recorded for this study in the Florida Keys appeared to either be leaders or followers. Followers were unlikely to become leaders, and the same was true of the reverse. And when leaders chose to change direction, it was more likely that the group would follow.

Having knowledgeable leaders in bottlenose groups in the Florida Keys is hugely important because of the risk of becoming stranded in isolated pools when the tide is out. It appeared that mothers often led the groups (identified as such because of the calves trailing close behind), but because dolphins in this area do not exhibit sexual dimorphism, it’s not easy to tell if leaders are always mothers or if this was just chance.

Megan was careful to point out that it’s common to overgeneralize when studying dolphins — folks often refer to “dolphins” as a group even though there are huge regional differences in dolphin society — so I want to be clear that the above points only necessarily apply to bottlenose dolphins in the Lower Florida Keys region.

Beyond that, it’s a question for further research.