A behavioral syndrome of competitiveness in a non-social rodent

Animals compete for limited resources such as food, mating partners, and territory. The outcome of this intraspecific competition should be determined by individual variation in behavioral traits, such as aggressiveness and dominance status. Consistent among-individual differences in behavior likely contribute to competitiveness and predispose individuals to acquire specific dominance ranks during parts of their adult life. Nevertheless, how dominance rank is correlated with animal personality traits remains largely unclear. In a first step towards better understanding these functional links, we studied trait integration into behavioral syndromes, using 26 captive male bank voles (Myodes glareolus). We repeatedly assessed boldness in an emergence test, exploration in an open-field test, aggressiveness in staged dyadic encounters, and the among-individual correlations between these behaviors. We further related these personality traits to dominance rank, from quantifying urine marking value (UMV), as marking in bank voles is related to dominance rank. We found repeatable variations in boldness, exploration, aggressiveness, and UMV, which were correlated at the among-individual level. Aggressiveness tended to be negatively correlated with body condition, a proxy for fitness. Thus, key personality traits and social rank are functionally integrated into a behavioral syndrome of intraspecific competitiveness. By joining social and non-social aspects of personality, our findings contribute to the ecological validation of personality traits and suggest how they contribute to higher-order component traits, such as dominance which directly affect fitness components.