Decoupling the effects of food and density on life history plasticity of wild animals using field experiments: Insights from the steward who sits in the shadow of its tail, the North American red squirrel

Long-term studies of wild animals provide the opportunity to investigate how phenotypic plasticity is used to cope with environmental fluctuations, and how the relationships between phenotypes and fitness can be dependent upon the ecological context.

Most previous studies have only investigated life history plasticity in response to changes in temperature, yet wild animals often experience multiple environmental fluctuations simultaneously. This requires field experiments to decouple which ecological factor induces plasticity in fitness-relevant traits to better understand their population-level responses to those environmental fluctuations.

For the past 32 years, we have conducted a long-term integrative study of individually marked North American red squirrels (Tamiasciurus hudsonicus Erxleben) in the Yukon, Canada. We have used multi-year field experiments to examine the physiological and life history responses of individual red squirrels to fluctuations in food abundance and c...