Seasonal and diurnal dynamics of glucocorticoids and behavior in giant pandas

Abstract Because of the suppressive effect of stress on reproduction and health, it is important to evaluate potential stressors that may compromise captive breeding programs for endangered species. However, behavioral and physiological measures of stress are sometimes difficult to interpret, and their relationship to stress can be obscured by factors unrelated to stress, such as seasonal and diurnal patterns. Here we present findings for daily and seasonal variation in glucocorticoid (GC) secretion and behavior from a 6-year study of 2 giant pandas (Ailuropoda melanoleuca). In the American black bear (Ursus americanus), seasonal patterns of corticoid secretion are putatively linked to metabolic demands of hibernation. Although pandas do not hibernate, we have found a similar pattern of GC dynamics. Using radioimmunoassay of urinary GC metabolites, we found seasonal variation in GC levels in an adult female and an adult male panda. As in black bears, winter and spring GC levels were significantly higher t...