Here today, not gone tomorrow: long-term effects of corticosterone

Abstract

There is a growing body of evidence from across animal taxa that exposure to elevated levels of glucocorticoids during development can have profound long-term effects upon physiological and behavioral phenotypes. Several avian studies have revealed that the degree to which an individual’s hypothalamo–pituitary–adrenal (HPA) axis responds to stressful stimuli as an adult may in effect have been ‘programmed’ or set as a result of that individual’s corticosterone exposure in ovo or as a nestling. Developmental exposure to corticosterone may also have effects upon avian ‘personalities’ or coping styles, and evidence from mammalian studies suggests that these long-term effects are mediated epigenetically via altered expression of relevant DNA sequences. Although there does not appear to be a consistent across-species pattern, developmental exposure to elevated corticosterone levels may shape adult coping style with such exposure, resulting in adults that are more timid and with increased HPA axis responsiveness to stress than those individuals that were exposed to relatively little corticosterone as nestlings. Recent work in Florida Scrub-jays (Aphelocoma coerulescens) has found that baseline corticosterone levels in nestlings at 11 days post-hatch explained 84% of the variation in ‘personality’ (bold vs. timid) when those individuals were tested at approximately 7 months of age. The overall ‘personality’ scores at 7–8 months of age were based upon tests that evaluated and combined the Jays’ responses to three tests: two startle and one neophobia stimuli. Here, we present findings on some of the factors that contribute to corticosterone levels of nestling Florida Scrub-jays, both within and among broods. Our prior and continuing research, as this overview will present, suggests that maternal attentiveness at the nest and paternal provisioning are important factors that mediate nestling corticosterone levels.