Evidence for Environment-Specific Pace-of-Life Syndromes

The pace-of-life syndrome (POLS) hypothesis posits that consistent individual differences in behaviour are integrated with physiology and life-history traits such that behaviour mediates how individuals resolve life-history trade-offs. For instance, individuals exhibiting higher exploration tendencies may accelerate reproduction by gaining access to resources more quickly, but this same behaviour could reduce survival through increased risks of predation and competition. While empirical support for POLS remains mixed, recent theory emphasises the role of environmental context in resolving some inconsistencies. Resource quality, in particular, may strongly mediate context-dependent effects, yet its functional role has received little empirical attention. To address this, we monitored the complete life-histories of 344 female house mice (Mus musculus domesticus) across four semi-natural enclosures running in parallel, provisioned with either high or standard-quality food. We first assessed how resource quality influenced life-history traits and then repeatedly measured behaviour to investigate the among-individual correlations between behaviour and life-history within each food quality treatment. Two axes captured most of the variation in life-history in both food quality treatments, with the primary axis reflecting a fast-slow continuum. The relationship between behaviour and life-history was context-dependent at the among-individual level: under a lower quality treatment, more exploratory females exhibited a faster pace-of-life, consistent with a risk-mortality trade-off. By contrast, in higher quality food conditions, individuals that covered more distance in an open-field, that is, more active stress-copers, delayed reproduction and followed a slower pace-of-life, suggesting a POLS that incorporates aspects of asset protection. Our results indicate that pace-of-life syndromes are context-dependent, emerging most clearly when behavioural variation interacts with environmental factors that affect some aspect of fitness. More broadly, we provide evidence that POLS vary profoundly in different ecological conditions, highlighting the importance of considering environmental context when testing fundamental links between behaviour and life-history.