Elian et al.

Extensive research has been devoted towards understanding the significance of animal personality, particularly in exploring potential links between consistent individual differences in behavioural traits and other underlying traits. The ‘personality-productivity’ hypothesis suggests a link between behaviour and individual differences in life-history traits, whereby individuals that are highly productive (grow fast, reproduce often) are expected to be more active, aggressive and bold, traits which are likely to contribute to growth-mortality trade-offs. Here, we tested the relationship between boldness (measured as latency to deconglobate from a defensive posture), growth rate, and survival in pill bugs (Armadillidium vulgare) in a controlled lab environment. We concurrently measured boldness and body mass on 94 individuals, once per week for 18 weeks, for a total of 1,168 paired measurements, and analysed the data using bivariate random regression model which accounted for among- and within-individual covariance between mass, growth and boldness. Despite significant variation in boldness, plasticity in boldness and growth rate, we found that neither boldness nor plasticity in boldness were correlated with growth rate. However, we found a significant positive among-individual correlation between latency to deconglobate and body mass, which support the asset protection principle at the among-individual level (i.e., large individuals were shy, small individuals were bold). By contrast, the within-individual correlation between latency to deconglobate and body mass was negative, suggesting the role of correlated plasticity in response to another state variable (e.g., metabolic rate, hydration levels). Overall, the study provides no evidence for the personality-productivity hypothesis, but does show evidence of state-behaviour relationships between boldness and body mass.