Maternal glucocorticoids have minimal effects on HPA axis activity and behavior of juvenile wild North American red squirrels

ABSTRACT As a response to environmental cues, maternal glucocorticoids (GCs) may trigger adaptive developmental plasticity in the physiology and behavior of offspring. In North American red squirrels (Tamiasciurus hudsonicus), mothers exhibit increased GCs when conspecific density is elevated, selection favors more aggressive perhaps active under these conditions. We tested hypothesis that elevated cause shifts offspring prepare them for high-density experimentally during gestation or early lactation. measured two behavioral traits (activity aggression) weaned using standardized assays. Because influence hypothalamic–pituitary–adrenal (HPA) axis dynamics, which turn affect behavior, we also impact our treatments on HPA dynamics (adrenal reactivity negative feedback), association between behavior. Increased lactation, but not gestation, slightly activity levels Offspring aggression adrenal did differ treatment groups. Male, female, from treated with pregnancy exhibited stronger feedback compared those control mothers, there were no differences lactation higher (both controls GC-treated) lower activity. These results suggest alone be sufficient cue produce substantial changes physiological stress responses natural populations.