Experienced problem solvers? The ontogeny of innovation in wild house mice

Animals frequently encounter challenges requiring innovative problem solving, yet an individual's propensity to innovate is believed to change throughout life. It is still unclear how age and experience interact to shape problem-solving performance over time. Here, we investigate how juvenile and adult wild house mice, Mus musculus domesticus , spontaneously engage with and solve novel problems by combining observations from populations living in two conditions, either socially complex seminatural enclosures or in more controlled, laboratory cages. There, we ran experiments to assess (a) the onset of problem-solving behaviours in preweaned mice, (b) spontaneous problem solving across age groups and (c) whether exposure to already solved set-ups improves problem-solving performance. We found that mice interacted with novel problems well before independence, and juveniles began solving problems before reaching sexual maturity. We also observed a contrasting pattern regarding age and performance. Specifically, juveniles and adults performed similarly in spontaneous problem solving when tested alone in standardized cage housing, but adults were more successful in the seminatural enclosures. Individual problem-solving performance remained highly consistent within each housing condition (that is, seminatural enclosures or cages), and exposure to solved set-ups did not help nonsolvers solve novel problems in either condition. In contrast, experience only benefited individuals that were already solvers, allowing them to solve more problems at a later time. Our results suggest that the ability to spontaneously problem solve is an inherent trait in house mice rather than a skill acquired through experience.