Snake personality: Differential effects of development and social experience

Personality traits are consistent across time and context, by definition, but the expression of personality in behavior is affected by both developmental and environmental factors. Little is known about the long-term effects such factors have on stability and change in personality traits, especially in understudied species. Research on species with different ecologies than more commonly studied mammals and birds can provide valuable insight into environmental influences on the stability of personality. We performed two experiments to investigate boldness and sociability in Eastern gartersnakes ( Thamnophis sirtalis ) in the laboratory. We first examined the developmental trajectories of these personality traits across the first 8 months of snakes’ lives. Next, we tested whether one month of social isolation could drive changes in either trait. Boldness and sociability displayed two different patterns of consistency and change. Across early development, gartersnakes display a shy–social correlation and are consistent in their boldness but not their sociability. Social isolation in contrast leads to changes in boldness for some snakes, while sociability remains consistent. These patterns of change are moderated by both sex and weight and may serve to drive male-biased dispersal of larger snakes early in life, and their re-settlement later on. In females, trait flexibility may help to balance the benefits of socializing while minimizing competition over food. These results highlight how the dynamics of personality development and stability may vary across taxa, driven by differences in ecology. Significance statement How personality traits are expressed in response to developmental changes and environmental pressures is an active area of research. Many studies of personality in non-human animals look for consistency in personality across short periods of time, and in response to moderate environmental change—methods that may miss important developmental changes. Here, we tested for changes in gartersnake personality during the first 8 months of development—an important time period for dispersal and resettlement, and in response to a change in their social environment. We found evidence that the expression of personality is trait-specific. For gartersnakes, boldness is consistent across time but changes in response to the social environment, whereas sociability displays the opposite pattern. These patterns of personality expression are different from more typically studied laboratory animals and emphasize the importance of studying species that experience a variety of selective pressures and social environments.