Age-dependent repeatability measurements of individual behavioural traits in Eurasian harvest mice (#306)
Animal personalities are known as consistent individual behaviours throughout time and across different situations. Recent data contradict the previous basic assumption of sex and age independent individual consistency. For example, males and females may differ in the repeatability of behavioural traits. Furthermore, activity seems to be the most consistent trait at different life history stages of rodents, while boldness and exploration show less consistency. Individual and temporal variance in behavioural consistency may therefore depend on sex and age classes, but also on the variance in expected future reproductive success. If so, sexual experience may have an impact on behavioural consistency, a currently little explored hypothesis. We measured the repeatability of four behavioural traits in Eurasian harvest mice (Micromys minutus). We compared repeatability estimates among four different age classes before and after maturation, and before and after the first sexual experience. We predicted that activity parameters show more consistent repeatabilities in all age classes compared to boldness and exploration. Due to a more stable environment for animals without sexual contact, we further assumed that adult mice without sexual contact show more repeatable behaviours compared to individuals which experienced sexual contact between tests. Our results indicate that harvest mice behaved repeatable in all age classes. Activity in an Open Field test was highly repeatable independent of age, but activity measured in a Y Maze showed less consistent repeatability measurements. The repeatability estimates of Y Maze activity increased significantly with age, but unexpectedly, boldness and exploration showed consistent repeatability patterns. Moreover, contrary to our expectations, adult mice behaved repeatable irrespective of their sexual experiences. We conclude that Eurasian harvest mice show highly consistent individual behaviours independent of age classes, despite the fact that repeatability in Y Maze activity increased significantly with age. Furthermore, sexual experience does not influence behavioural consistency in this species.