Food quality-driven variation in the link between innovation and survival in semi-natural populations of wild mice.

Innovation underpins adaptation to environmental challenges, yet its link to fitness remains unclear. This may reflect context-dependent effects, with fitness benefits emerging primarily under poor environmental conditions or among individuals in poorer condition. However, empirical tests linking innovation to fitness across environments in continuously monitored individuals remain rare. Here, we manipulated environmental quality in young wild house mice by providing either a high- or a comparatively lower quality diet. We quantified innovation propensity and latency early in life, using standardized tasks, and subsequently released individuals into semi-natural environments that matched their developmental diet. We then tracked body mass (as a proxy for fitness) and survival over six months. We tested whether the effects of innovation propensity and latency on fitness were more pronounced among individuals living in lower-quality conditions, as predicted by the necessity drives innovation hypothesis. Mice on the high-quality diet were more innovative. Moreover, while innovation propensity did not predict body mass trajectories, survival depended on an interaction between innovation latency and environmental quality, indicating environment-dependent fitness trade-offs. Our findings demonstrate that the fitness consequences of innovation are contingent on environmental variation, which may help explain inconsistent patterns reported across studies.