Evidence for the ‘behavioural character’ hypothesis: does boldness programme disparate antipredator strategies?

Risk-taking behaviours that are optimal in one context (predators absent) may be suboptimal in a different context (predators present), suggesting that individuals with ‘bold’ behaviours will experience increased predation risk. Yet, in some instances, bold individuals experience lower predation. Thus, there is not always a direct trade-off between boldness and predation risk. To better understand the relationship between boldness and predation risk, suboptimal behaviours must be viewed within the context of an organism's entire integrated antipredator strategy. Using freshwater snails exposed to a predator cue, we examined whether quickly re-emerging from the shell was a repeatable, carryover behaviour that was tied to behavioural and morphological antipredator traits. Slow-emerging snails invested in morphological shell defence and remained in the predator environment, whereas quick-emerging snails consistently avoided the predator environment and did not invest in shell defences. Therefore, slow-emerging snails used a sit-and-wait antipredator strategy by relying on their shells for protection and were less likely to avoid the predator environment; conversely, quick-emerging snails used an avoidance (or dispersal) strategy by consistently associating with the water's surface and investing less in shell defences. A path analysis of these antipredator traits indicates that the carryover effect of bold behaviour may be an important factor that mediates complementary behavioural and morphological traits that reduce predation risks. This study supports the ‘behavioural character’ hypothesis, which suggests that boldness is a latent variable upon which selection can act and thereby shape a variety of quasi-independent traits (e.g. antipredator traits). According to this perspective, selection is not acting on a single antipredator behavioural trait in isolation, but rather on an integrated antipredator strategy that is facilitated by individual differences in carryover risk-taking behaviour.