No abstract

Trade-offs between behavioural traits promoting high life-history productivity and mortality may fuel the evolution of animal personalities. We propose that parasites, including pathogens, impose fitness costs comparable to those from predators, and influence the adaptiveness of personality traits associated with productivity (PAPs). Whether personality traits are adaptive or not may also depend on individual immunological capacity. We illustrate this using a conceptual example in which the optimal level of PAPs depends on predation, parasitism and host compensation (resistance and tolerance) of parasitism's negative effects. We assert that inherent differences in host immune function can produce positive feedback loops between resource intake and compensation of parasitism's costs, thereby providing variation underlying the evolution of stable personalities. Our approach acknowledges the condition dependence of immune function and co-evolutionary dynamics between hosts and parasites.

No abstract

No abstract

No abstract

Summary1. According to a recent hypothesis, personality traits should form integrative pace-of-life syndromes with life-history traits. Potential life-history traits that explain personality variation are immune defence and growth rate. 2. We studied whether boldness, measured as hiding behaviour, is repeatable during ontogeny in the field cricket, Gryllus integer, and if it relates to the efficiency of immune function (i.e. the capacity to encapsulate a nylon implant), growth rate, developmental time and size as an adult. 3. Hiding behaviour was rank-order repeatable, and in general, juveniles were bolder than adults. Individuals that were cautious at early juvenile stages had higher encapsulation responses late in life compared with bold individuals. Most clearly, fast-growing individuals matured early and invested little in immune defence compared with their slower-growing conspecifics, i.e. showed patterns of a 'grow fast, die young' life-history strategy. 4. Our results may arise from a trade-off between immunity-dependent survival and bold behaviour. Trade-offs between investment in survival and behaviour could account for the maintenance of variation in personality traits by favouring certain combinations of behavioural and life-history strategies (i.e. pace-of-life-syndromes).

Modern models for the evolution of conspicuous male mating displays assume that males with conspicuous displays must bear the cost of enhanced predation risk. However, if males can compensate behaviourally for their increased conspicuousness by acting more cautiously towards predators, they may be able to lower this cost. In the field cricket Gryllus integer, males call to attract females, and differ in their durations of uninterrupted trilling (calling-bout lengths). Differences among males in calling-bout lengths are heritable, and females prefer males with longer calling bouts. In this study, males with longer, more conspicuous songs behaved more cautiously than males with shorter songs on two different tests of predator avoidance. They took longer to emerge from a safe shelter within a novel, potentially dangerous environment, and they ceased calling for a longer time when their calls were interrupted by a predator cue. Thus, these males appear to compensate behaviourally for their more conspicuous mating displays. Additionally, latencies to emerge from a shelter in the novel environment were consistent over time for both individual males from the field and males that had been reared in the laboratory, indicating that the differences in latency among males may be heritable.

No abstract