Effects of Food Supplementation on Activity and Reproduction in the Eastern Chipmunk (Tamias striatus)

A key requirement for adaptive phenotypic plasticity is that environmental cues reliably predict future conditions. However, anthropogenic change and environmental stochasticity can disrupt these cues, leading to mismatches between phenotype and environment. We monitored a population of eastern chipmunks (Tamias striatus Linnaeus, 1758) in a deciduous forest in southern Québec, Canada, from 2013 to 2024, and conducted a supplemental-feeding experiment from 2022 to 2024 to examine how food availability influenced spring body mass, above-ground activity, and reproductive phenology, and whether cohort-level differences in activity affected reproductive success. Across the long-term study, unsupplemented populations showed a significant decline in spring body mass from 2013 to 2024, whereas supplemented populations maintained higher spring body mass. On the supplemented site, we observed cohort-level variation: cohorts born after the food supplementation began exhibited reduced above-ground activity and lower weaning success, likely due to missed breeding opportunities, which predominantly occur above-ground. These findings indicate that cues governing seasonal activity could be learnt early in life and act independently among generations within the same population. Our results highlight how early-life environmental cues can have lasting effects on physiology and behaviour under changing environmental conditions.