Personality-related survival and sampling bias in wild cricket nymphs

The study of adaptive individual behavior (animal personality) focuses on whether individuals differ consistently in (suites of correlated) behavior(s) and whether individual-level behavior is under selection. Evidence for selection acting on personality is biased toward species where behavioral and life-history information can readily be collected in the wild, such as ungulates and passerine birds. Here, we report estimates of repeatability and syndrome structure for behaviors that an insect (field cricket; Gryllus campestris) expresses in the wild. We used mark-recapture models to estimate personality-related survival and encounter probability and focused on a life-history phase where all individuals could readily be sampled (the nymphal stage). As proxies for risky behaviors, we assayed maximum distance from burrow, flight initiation distance, and emergence time after disturbance; all behaviors were repeatable, but there was no evidence for strong syndrome structure. Flight initiation distance alone predicted both daily survival and encounter probability: bolder individuals were more easily observed but had a shorter life span. Individuals were also somewhat repeatable in the habitat temperature under which they were assayed. Such environment repeatability can lead to upward biases in estimates of repeatability in behavior; this was not the case. Behavioral assays were, however, conducted around the subject's personal burrow, which could induce pseudorepeatability if burrow characteristics affected behavior. Follow-up translocation experiments allowed us to distinguish individual and burrow identity effects and provided conclusive evidence for individual repeatability of flight initiation distance. Our findings, therefore, forcefully demonstrate that personality variation exists in wild insects and that it is associated with components of fitness.