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Animal aggression depends on rank within social hierarchies

Results from a research project between Dan Mønster, AU and researchers from Santa Fe Institute has been published in PNAS.

2021.03.05 | Anne-Mette Pedersen

Photo: Tom Koerner/USFWS


Members of a social species need to make appropriate decisions about who, how, and when to interact with others in their group. However, it has been difficult for researchers to detect the inputs to these decisions and, in particular, how much information individuals actually have about their social context. We present a method that can serve as a social assay to quantify how patterns of aggression depend upon information about the ranks of individuals within social dominance hierarchies. Applied to existing data on aggression in 172 social groups across 85 species in 23 orders, it reveals three main patterns of rank-dependent social dominance: the downward heuristic (aggress uniformly against lower-ranked opponents), close competitors (aggress against opponents ranked slightly below self), and bullying (aggress against opponents ranked much lower than self). The majority of the groups (133 groups, 77%) follow a downward heuristic, but a significant minority (38 groups, 22%) show more complex social dominance patterns (close competitors or bullying) consistent with higher levels of social information use. These patterns are not phylogenetically constrained and different groups within the same species can use different patterns, suggesting that heuristic use may depend on context and the structuring of aggression by social information should not be considered a fixed characteristic of a species. Our approach provides opportunities to study the use of social information within and across species and the evolution of social complexity and cognition.  




Elizabeth A. Hobson, Dan Mønster, and Simon DeDeo (2021): Aggression heuristics underlie animal dominance hierarchies and provide evidence of group-level social information. Proceedings of the National Academy of Sciences of the United States of America (PNAS).



The project started in 2015 where Dan Mønster received a IMC Seed Funding grant for the project "Rank Emergence through Conflict". Dan Mønster collaborates with researchers from Santa Fe Institute, where the co-authors come from. Read the press release about the research article from Santa Fe Institute here: Animal aggression depends on rank within social hierarchies