Integrating Nutrition and Stress into Life History Stages of Wild Free-Ranging Female Pronghorn

Studies addressing seasonal changes in diet quality and hormones are important for understanding the interactions between ecology and physiology. We collected fecal samples from free-ranging adult female pronghorn (Antilocapra americana) to examine the relationships between indicators of nutrition and glucocorticoid activity. This occurred during three population-level, life-history-correlated sampling periods across five subpopulations. We evaluated nutrition via fecal nitrogen, fecal 2,6-diaminopimelic acid (DAPA), and assessed glucocorticoid activity using fecal glucocorticoid metabolites (FGM). We found positive relationships between fecal nitrogen and DAPA, whereas DAPA and fecal nitrogen with FGM varied in influence and strength, depending upon life history stage. Generally, correlations between DAPA and FGM were strongest during late gestation sampling, whereas correlations between those two measures and fecal nitrogen lacked consistency across life history stages and years. We found that maternal nutrition and stress were associated with notable changes in the relative intake of dietary protein from plant functional groups across sampling periods. Pronghorn appeared to shift between diets high in nitrogen or digestible energy content, depending upon life history stage and associated metabolic demands. We feel these results will assist wildlife managers in further understanding relationships between physiological parameters and how pronghorn meet the metabolic requirements of life history stages.