Kirsten Sheehy

Dominance hierarchies are nearly ubiquitous across the animal kingdom. But how these hierarchies play out in animal groups with high rates of membership turnover are not well understood. My work seeks to describe how hierarchies affect an individual’s decision to leave or join a group.

Dominance hierarchies are nearly ubiquitous across the animal kingdom. But how these hierarchies play out in animal groups with high rates of membership turnover are not well understood. I work with the Amazon molly (Poecilia formosa), a naturally genetically clonal and all-female species of fish. Her unique biology and allows me to tightly control for both genetic and social contributions to hierarchy status. In order to tease apart the relative contribution of size and familiarity to an individual’s rank, I created 21 groups of four individuals and allowed them to form a hierarchy. I then removed the top ranked individual and allowed the remaining groups of three to settle into their new hierarchy. Then, to determine whether intrinsic characteristics or social experience were more important, I added the top ranked fish to either a familiar or unfamiliar group. In general, fish did not immediately re-attain their top rank. Interestingly, fish that were added to completely unfamiliar groups did worse, suggesting that familiarity is indeed important for hierarchy formation.