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Dryad

Environmental variability affects flexibility in activity onset at large geographic scales

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Feb 18, 2026 version files 68.19 KB

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Abstract

Timing is an essential component of the phenotype, influencing organism fitness and fundamentally shaping ecological interactions. Although variation in the timing of activity can be substantial, the degree to which this variation stems from behavioral flexibility (within-individual variation) vs. consistent behavioral differences (among-individual variation) is poorly understood and represents a key knowledge gap as these have different ecological and evolutionary implications. Whereas flexibility in timing may be advantageous in novel circumstances, individuals could also make mistakes. Alternatively, consistent among-individual differences in timing may lead certain individuals to exhibit maladaptive behavior when confronting novel conditions (e.g., light pollution or novel predators). We estimated activity onset from 1050 captures of 483 individual white-footed mice, Peromyscus leucopus, across the upper Midwest, Northeast, Mid-Atlantic, and southern Appalachia regions of the United States. In each locale, we quantified the total phenotypic variation in activity onset and partitioned this into its within- and among-individual components. We then examined whether mice at locations experiencing more variable climate or residing in more structurally variable habitats exhibited differences in within- or among-individual variation in timing. We found that timing flexibility was always greater than consistency, and individuals from populations at cooler, drier sites with variable seasonal precipitation and temperature were more flexible than mice at warmer, wetter sites with less seasonal change in precipitation and temperature. Behavioral flexibility was not significantly associated with habitat structure heterogeneity. Our results reveal that most variation in timing across the range of this species derives from within-individual variation.