State-dependent changes in risk-taking behaviour as a result of age and residual reproductive value

Abstract

Animals are able to modify their behaviour in response to changes in their internal and environmental state. The asset protection principle predicts that an animal's risk-taking behaviour should vary as a result of its residual reproductive value (RRV); animals with greater RRV would incur a greater cost if injured or killed and should therefore take fewer risks than those with low RRV. Despite the intuitive appeal of this hypothesis, few studies have effectively separated the effects of RRV on behaviour from those of age. We addressed this weakness in the widely invoked hypothesis by measuring the risk-taking behaviour of female Australian field crickets, Teleogryllus oceanicus, at various points in the animal's lifetime. We found significant effects of age on risk-taking behaviour: older females emerged from a shelter sooner after a simulated predation threat and exhibited greater mobility in an open arena. Importantly, there was also a significant marginal effect of RRV on risk-taking behaviour. Females with lower RRV displayed greater levels of risk taking than females with high RRV. Our results thereby offer support for the asset protection principle as an explanation for state-dependent variation in risk-taking behaviour.