Hierarchies inferred from different agonistic behaviours are not always comparable.

Abstract

Social hierarchies are widely used to predict life-history patterns and priority of access to resources. Yet, behavioural ecology and social sciences lack a consistent relationship between specific behaviours and social rank across studies. I used published data sets from 42 groups of 25 species representing several taxa to determine whether hierarchies inferred from different behaviours are similar or (in)consistently different at both individual and group levels. Ranks inferred from yielding interactions in the absence of aggression ('ritualized') were often comparable to ranks inferred from decided aggression (unambiguous outcome) but not to ranks inferred from undecided aggression. Accordingly, hierarchies inferred from data sets including only decided interactions were steeper than those inferred from data sets including undecided aggression. These results support the hypothesis that aggression can be context-dependent and might reflect less stable or mutually recognized relationships than (ritualized) yielding interactions. I discuss the consequences of choosing different behaviours to infer social hierarchies and the difficulty of making generalizations from one species or taxon to another. Finally, I recommend that the use of ritualized yielding and certainly the use of decided over undecided interactions to infer social hierarchies should be preferred, especially in comparative studies which go beyond taxon-specific idiosyncrasies.