Long-term behavioral repeatability in wild adult and captive juvenile turtles (Terrapene carolina): Implications for personality development

Animal personality can be defined as conspecific individuals consistently differing in behavioral tendencies. Personality is typically identified by behavioral repeatability, which occurs when within-individual variance is low relative to among-individual variance in the population. Intraspecific comparisons of behavioral repeatability in juveniles and adults within and across years are rare, but would be useful for testing hypotheses related to origins of animal personality and whether individuals exhibit stable or diverging behavior with ontogeny. To examine within- and across-year behavioral repeatability for eastern box turtles (Terrapene carolina), we assessed boldness (movement latency after brief confinement) of captive-born juveniles twice within three days when eight months old. We then repeated these tests for the same individuals one year later. Juveniles exhibited repeatable boldness within and across years. Although increasing body temperature was slightly associated with decreased movement latency, test year (1 or 2), or housing experience (being raised in an enriched or unenriched condition) had no effects on boldness. We also assessed across-year repeatability of boldness (head emergence from the shell after brief confinement) for wild adults at 1–3 year intervals. Adults also exhibited repeatable across-year boldness that was of similar magnitude to juveniles. We found no indication that sex class or whether adults had been radio-tracked influenced boldness. Our results suggest eastern box turtles demonstrate consistent individuality in boldness from an early age that is largely unaffected by temporal or environmental variation, and these behavioral differences can be maintained for multiple years in captivity and the wild, contrasting with theoretical expectations for personality development. These findings add to recent accumulating evidence demonstrating juvenile and adult box turtles exhibit multiple repeatable behaviors over the short- and long-term. We suggest this species is quickly gaining traction as a model organism for studying the proximate and ultimate causes of personality development within long-lived animals.