An alternative hypothesis for the evolution of sexual segregation in endotherms

Aim: Patterns of separation among males and females, known as sexual segregation, are traditionally correlated with elevation or latitude in animals. Alternatively, in humans, spatial and behavioural segregation is driven by inherent sex-based differences in thermal preference, although the cause and adaptive value of these differences remain unclear. Here, we explore whether, similar to humans, ambient temperature can explain patterns of separation among males and females in endotherms. Location: Israel. Time period: 1981–2018. Major taxa studied: Migratory sexually dimorphic birds (13 species) and bats (18 species). Methods: We calculated the proportion of males and females at each sampling site for each bird or bat species. We used general linear mixed models (GLMMs) to quantify the variance explained by elevation, latitude, body size and ambient temperature and corrected for phylogeny, site and year. We used model averaging over the best models by comparing the corrected Akaike information criterion. Results: We found a correlation between geographical separation and temperature that accounted for variance in the data that was not explained by elevation and latitude. We showed that temperature was negatively correlated with the proportion of males in bats and birds, whereas body size explained this response only in birds. Main conclusions: Our findings suggest that females are found in higher ambient temperatures. We term this differential sex-related thermal preference (DSTP) and propose that it is a broad phenomenon common in many endotherms, acting as a significant force shaping dispersal, sociality and behaviour of animals, and should be explored from this wide perspective.