Behavioral type and corticosterone responsiveness are linked in Florida scrub-jays: exploring causes and consequences of physio-behavioral phenotypes (#494)
Our long-term study of free-living Florida scrub-jays (FSJ, Aphelocoma coerulescens) has revealed a strong relationship between an individual’s hypothalamic-pituitary-adrenal axis response during capture-and-handling stress and behavioral type. The physiological response and behavioral type covary, leading to our coining the term physio-behavioral phenotype. Low stress-induced corticosterone (SI-CORT) responders are less neophobic, more exploratory, and better at associative, yet worse at reversal (i.e., less flexible), learning when compared to high SI-CORT FSJs. Ongoing monitoring reveals that the SI-CORT responsiveness (and to a lesser degree, baseline CORT levels) and behavioral type persist over much, if not the entirety, of an individual’s life. Some propose that behavioral flexibility be considered in selecting individuals for managed translocations (FSJs are a threatened species), as boldness and adaptability would be essential in new environments. Similarly, flexibility also could allow individuals to differentially adapt to changing environments associated with global climate change. We continue to investigate causes and consequences associated with physio-behavioral phenotypes which are seemingly shaped early in life as is indicated by our findings that: 1) better parenting (e.g., higher maternal nest attendance and paternal food delivery) leads to lower nestling CORT levels; 2) baseline CORT levels of nestlings predict degree of boldness 8 mo later; 3) food supplemented nestlings had lower SI-CORT responses at nutritional independence (~70 d post-hatch), a characteristic that persisted through 2 years; 4) broods with a CORT-treated nestling beg more than control broods and nestling begging rate predicts SI-CORT response at nutritional independence and when 1-yr-old; and 5) SI-CORT responses at independence predict boldness 6-8 months later. Given these findings, it’s clear that multiple developmental influences are in play. The physio-behavioral phenotype is also associated with sex-specific differences in lifespan. Low SI-CORT, bold males live longer whereas the opposite is true for females. We speculate that the sex-specific division of labor during reproduction results in different energetic costs and predation risks for male and female FSJs with similar phenotypes.