Annemarie van der Marel , Xavier Francis, Claire L. O'Connell, Cesar Omar Estien, Chelsea E Carminito, Elizabeth A. Hobson

Recent computational approaches discovered group-level patterns within dominance hierarchies which are based on relative rank differences between individuals. Within species, groups could follow different dominance patterns, indicating these patterns could be group- rather than species-specific traits. Moreover, these patterns differ in complexity, with some requiring an individual to access more social information than others. However, we know little about how and why a particular dominance pattern emerges within a group. To address what social dynamics inform a group’s pattern use, we performed social perturbation experiments in four captive groups of monk parakeets (Myiopsitta monachus) via removals and reintroductions of differently ranked birds creating social instability. We found that 1) dominance patterns can shift over time within a group after removal of top-ranked birds, 2) the perturbed individual’s rank resulted in different group-level responses, 3) patterns remained stable within a group when we did not experimentally perturb the system, and 4) groups did not shift to less informative patterns after perturbations. When we removed top-ranked birds, groups were more likely to bully that bird, piling aggression onto it upon its reintroduction, whereas the removal of a middle/low-ranking bird was associated with a downward heuristic pattern, where individuals aggress indiscriminately against others ranked below themselves. Dominance patterns shifted upon reintroductions more consistently than after removals of top-ranked birds. This work shows group-level plasticity in social dominance patterns as groups vary in their patterns over time and shows that social instability is one mechanism for a group to shift patterns.