The fast and the curious III: speed, endurance, activity, and exploration in mice

Given that organismal performance (e.g., sprint speed, endurance) sets the envelope within which behaviour is possible, there are likely many co-adaptations between suites of performance and behavioural traits. On one hand, performance might compensate for behaviours that increase predation risk, such that bold and active individuals should be able to sprint faster and/or for longer. On the other hand, performance could be co-specialised with behaviour to reduce overall predation risk, such that shy and inactive individuals should be able to sprint faster and for longer. Here, we repeatedly measured multiple aspects of locomotor performance (sprint speed and swimming performance) and behaviour (exploration, voluntary wheel running, and home-cage activity) in 51 female white-footed mice (Peromyscus leucopus). All six among-individual correlations between the behavioural and performance traits were negative. Sprint speed was significantly negatively correlated with both voluntary wheel running and home-cage activity, such that faster sprinters travelled less distance on the wheel and in their home cage. By contrast, the within-individual correlation between sprint speed and voluntary wheel running was positive and significant, providing another striking example of the importance of partitioning the correlations among labile traits. Our results suggest that the performance-behaviour link is not caused by methodological biases due to measurements in stressful situations (e.g., escape from human threat, exposure to a novel environment). Our study, combined with others on performance and behaviour, provide unequivocal support for co-specialisation in rodents, but also raises the interesting possibility that plastic within-individual changes in performance and behaviour follow a compensatory relationship.Significance statementTo minimise predation risk, animals can behave in such a way to avoid exposure to predators and/or rely on their locomotor performance (to outrun predators). On one hand, bold individuals may compensate for higher predation risk by having greater locomotor performance whereas, on the other hand, behaviour and performance may be co-specialised, in which case shy individuals would have greater locomotor performance. Here we found that, on average, individuals that are more active have lower maximal sprint speed, but on a given day, individuals that are more active than usual display faster sprint speed (relative to their own individual average). Hence, performance and behaviour appear co-specialised at the among-individual level, but plastic changes in performance and behaviour follow a compensatory relationship, which highlights the importance of (co)variance partitioning to properly separate relationships at the among- and within-individual levels.

Automated summary

Given that organismal performance sets the limit for behavior, there are likely co-adaptations between performance and behavioral traits. Performance might compensate for risky behaviors, allowing bold individuals to sprint faster and for longer. Performance could also be co-specialized with behavior to reduce predation risk, allowing shy individuals to sprint faster and for longer.