Drivers of intraspecific lethal aggression in mammals

Aim To assess whether interspecific variation in lethal intraspecific aggressiveness in mammals exhibits a geographical gradient and, if so, to identify which ecological, social and evolutionary processes could explain such patterns. Location Global. Taxon Mammalia. Methods We mapped intraspecific lethal aggressivity for 952 terrestrial mammal species and, through an assemblage-based and phylogenetic approach, tested at a global scale four hypotheses that may explain differences in lethal aggressivity: the seasonal effects of photoperiod seasonality, food resource availability, social organisation and evolutionary history. Results Photoperiod seasonality, which is linked to hormonal control, was the best predictor of lethal aggressivity. However, interactions between the environment and evolutionary factors explained the higher proportion of interspecific variation. Main conclusions The geography of behavioural traits, affecting multiple adaptive pathways, is an important emerging area of biogeographical research with high potential relevance for interpreting other macroecological patterns.