Risk-taking and risk-avoiding behaviors by hermit crabs across multiple environmental contexts

Animal personality can affect individual fitness and the dynamics of populations. This study tested variation in risk-avoiding (emergence from shells) and risk-taking behaviors (abandoning shells) within a cohort of hermit crabs (Clibanarius vittatus) under a range of environmental stimuli. The startle response (SR) of individuals to predators (negative stimuli) and cues that signal new shells (positive stimuli) was measured under contrasting scenarios of shell condition (intact vs. damaged). The abandonment response (AR) of the same individuals was then measured following entrapment to further test consistency in individual behavior. SR varied according to stimuli and shell condition, with individuals showing a faster response to predators when inhabiting intact shells, than damaged shells that made them more vulnerable. Interestingly, the response to gastropod cues was faster when individuals were in damaged shells, possibly reflecting greater motivation to investigate new resources. When assessing the SR of individual subjects, strong correlations were observed across the different trial combinations (14 out of the 15), suggesting that the behavior of an individual under one set of treatment conditions, is a good predictor of its behavior under other conditions. AR similarly varied with shell condition, with crabs more likely to abandon damaged, rather than intact shells. Multivariate analysis linking these suites of behaviors (predator SR + gastropod SR + entrapment AR) highlighted consistent among individual variation in behavior driven by distinct responses to stimuli. Overall, we show that hermit crabs can exhibit unique personality traits that will influence their survival and fitness in environments where predation risk and resource availability vary over short spatial and temporal scales.