Long-term repeatability and stability of three personality traits in meadow voles

Consistency of animal personality traits is expected. Mounting evidence suggests that animal personalities will change with time and major life events. Research into this phenomenon is often limited to span only short periods of time in the animals’ life or have few measures across their life. We measured Exploration, Activity and Boldness of litters of meadow voles, Microtus pennsylvanicus, in a pair of novel object tests six times over a year, representing a large proportion of the lifespan of the vole. Our null hypothesis was that the personality traits would not change, and our first alternative hypothesis was that personality traits would change equally for all individuals as they aged. Neither was supported. The data support our third hypothesis that traits would change and change unequally. Activity and Boldness were consistent across time. However, Exploratory behaviour increased with the vole\u27s age. The supported models show that personality traits change consistently for related individuals, but the litters differ in their change with age. This suggests that meadow vole life history affects how personality traits develop, but not necessarily their magnitudes. We also tested the repeatability of traits across the testing intervals. We discovered that the repeatability of these three personality traits varied across time, depending on the trait. Activity was repeatable equally across ages. Exploration became more repeatable and Boldness became less so. Thus, personality traits may be more malleable than supposed, especially over long periods of time