Is Early Life Adversity Associated With Adult Stress in a Wild Rodent?

The period before sexual maturity is a sensitive life stage where most development and change occur. Studies in humans and other animals show that early adverse experiences contribute to poor health and survival. However, the mechanisms are still unclear. Some have found that early life adversity (ELA) can lead to elevated glucocorticoids later in life, dysregulate the stress response, and increase the impact of later stressors. However, most animal studies have focused on individual stressors. Protecting wild populations that are exposed to multiple stressors requires a better understanding of the physiological consequences of several co-occurring stressors. We used a cumulative adversity index (CAI) to ask whether early adverse experiences were associated with increased levels of adult fecal glucocorticoid metabolites (FGM) in wild female yellow-bellied marmots (Marmota flaviventer). We found a significant interaction between adversity and elevation that explained variation in FGMs. Thus, we infer that ELA can modulate FGMs, but contrary to similar research in other mammals, the trend was toward downregulation under more environmentally relaxed conditions (lower elevation). Our results highlight the value of studying the relative importance of early and later stressors in the physiology of different wild taxa when investigating the mechanisms of early life adversity.