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Rearing-group size determines social competence and brain structure in a cooperatively breeding cichlid.

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Fischer, Stefan 
Bessert-Nettelbeck, Mathilde 
Kotrschal, Alexander 
Taborsky, Barbara 


Social animals can greatly benefit from well-developed social skills. Because the frequency and diversity of social interactions often increase with the size of social groups, the benefits of advanced social skills can be expected to increase with group size. Variation in social skills often arises during ontogeny, depending on early social experience. Whether variation of social-group sizes affects development of social skills and related changes in brain structures remains unexplored. We investigated whether, in a cooperatively breeding cichlid, early group size (1) shapes social behavior and social skills and (2) induces lasting plastic changes in gross brain structures and (3) whether the development of social skills is confined to a sensitive ontogenetic period. Rearing-group size and the time juveniles spent in these groups interactively influenced the development of social skills and the relative sizes of four main brain regions. We did not detect a sensitive developmental period for the shaping of social behavior within the 2-month experience phase. Instead, our results suggest continuous plastic behavioral changes over time. We discuss how developmental effects on social behavior and brain architecture may adaptively tune phenotypes to their current or future environments.


This is the author accepted manuscript. The final version is available from The University of Chicago Press for The American Society of Naturalists via


Aggression, Animals, Behavior, Animal, Brain, Breeding, Cichlids, Cooperative Behavior, Social Behavior, Social Environment

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University of Chicago Press
We acknowledge financial support from the Swiss National Science Foundation (31003A_133066 to B.T. and P2BEP3_155614 to S.F.), the Foundation Pierre Mercier, and the Austrian Science Fund (J 3304-B24 to A.K.)