Risk Predictability in Early Life Shapes Personality of Mosquitofish in Adulthood

SIMPLE SUMMARY: Animal personality refers to consistent behavioral differences among individuals, which have been found to exist in many animal species. Although personality is largely determined by genetic factors, it might be greatly influenced by external environmental factors, e.g., risk pattern, which is still poorly known. In this study, newborn mosquitofish, Gambusia affinis, were reared to sexual maturity under different treatments of risk predictability (i.e., no risks, unpredictable risks, risks at 5 min after feeding and risks at 2 h after feeding) to investigate the effect of risk predictability in early life on their personality traits (i.e., shyness and exploration). We found that mosquitofish’s exploration showed repeatability in all risk treatments, while the shyness of the fish was repeatable only in the predictable risk treatments. Shyness was negatively related to exploration in the three risky treatments, no matter predictable or unpredictable. The fish reared under predictable risk were less explorative, and we did not find differences in shyness across treatments. These findings suggest that risk predictability in early life may be important in shaping animal personality. ABSTRACT: Animal personality is of great ecological and evolutionary significance and has been documented in many animal taxa. Despite genetic background, personality might be prominently shaped by external environments, and it is significant to explore the environmental factors that influence the ontogeny of animal personality in early life. Here, we reared newborn mosquitofish Gambusia affinis under different treatments of risk predictability (i.e., no risks, unpredictable risks, risks at 5 min after feeding and risks at 2 h after feeding) and measured their two personality traits at sexual maturity. We measured the behavioral repeatability, correlation between behavioral characteristics, and the impact of risk predictability. We found that the fish showed repeatability in exploration in all risk treatments, as well as repeatability in shyness under predictable risks. When growing up in risk treatments, no matter predictable or unpredictable, shyness and exploration showed a negative correlation, suggesting a behavioral syndrome between the two behavioral traits. The fish reared under predictable risks were less explorative than those under unpredictable risks, while there were no differences in shyness among treatments. Besides, smaller fish were bolder and more explorative than larger ones. Our findings imply that risk predictability in early life may play an important role in shaping animal personality and modifying the average behavioral levels.