Lifespan and age, but not residual reproductive value or condition, are related to behaviour in wild field crickets

Abstract

Individuals frequently show long-term consistency in behaviour over their lifetimes, referred to as “personality.” Various models, revolving around the use of resources and how they are valued by individuals, attempt to explain the maintenance of these different behavioural types within a population, and evaluating them is the key for understanding the evolution of behavioural variation. The pace-of-life syndrome hypothesis suggests that differences in personalities result from divergent life-history strategies, with more active/risk-taking individuals reproducing rapidly but dying young. However, studies of w ild animals provide only limited support for key elements of this and related hypotheses, such as a negative relationship between residual reproductive value and activity. Furthermore, alternative models make divergent predictions regarding the relationship between risk-taking behaviours and variables consistent in the short-term, such as condition. To test these predictions, we regularly measured willingness to leave a shelter and the activity level of wild adult field crickets (Gryllus campestris) at both short and long intervals over their entire adult lives. We found some support for a pace-of-life syndrome influencing personality, as lifespan was negatively related to willingness to leave the shelter and activity. Crickets did not appear to protect their “assets” however, as estimates of residual reproductive value were not related to behaviour. Although there was considerable variance attributed to the short-term consistency, neither trait was affected by phenotypic condition, failing to support either of the models we tested. Our study confirms that behaviours may covary with some life-history traits and highlights the scales of temporal consistency that are more difficult to explain.