Sex differences and behaviour in the pace-of-life of rodents

Male and female rodents experience different selective pressures associated with reproductive costs. Thus, we may expect the expression of different Pace-of-life (POL) strategies between sexes. Further, the pace-of-life syndrome (POLS) hypothesis and anisogamy predict differences in the costs of gamete production, where variation in life history trait expression should follow a fast-slow continuum such that males and females might exist on opposite ends of the spectrum. However, males and females could express a similar POL strategy in systems where the reproductive costs are consistent between sexes or where selective pressures force a similar directionality of traits. We used standardized behavioural tests and fecal glucocorticoid metabolite (FGM) concentrations to measure potential differences in POL strategies among three rodent species in Algonquin Provincial Park. We hypothesized that differences in reproductive costs between males and females would result in differences in POL traits along the fast-slow continuum. We predicted that males would express more explorative behaviours and have a higher level FGMs than female counterparts. We found little support for the POLS hypothesis between sexes. Instead, we suggest that the species observed may express a similar directionality of selection for the observed behavioural traits, where both sexes express similar relationships in POL. Thus, some male rodents may be more explorative to accommodate the increase of energetic stress associated with mate acquisition, while females may share similar trait expressions to accommodate the increased metabolic demand for the care and development of young.