Hormones and Behavior: Why it isn't always black and white. (#267)
Testosterone and its effects on behavior have been widely studied in male birds. Early research in a variety of sparrow species presented strong evidence that testosterone impacts male behavior, particularly aggression, and that increases or decreases in this steroid hormone can lead to changes in male behavior (aggression, parental care). As scientists expand the species they work with, the variety of behavioral contexts that they explore, and even the types of hormones they measure it is becoming clearer that many of our original ideas regarding hormones and behavior need further investigation. While ideas like the ‘challenge hypothesis’ are excellent at explaining hormone-behavior relationships for a wide number of individuals and species, they may not cover all organisms and/or behaviors. Here I discuss findings comparing testosterone with aggressive and parental care behaviors in the northern cardinal (Cardinalis cardinalis) a species with atypical testosterone levels and behaviors that seem divorced from circulating testosterone. Findings from this work lend support to the idea that additional levels of hormone response, as well as, flexibility in what may be seen as an ‘appropriate’ situation for a hormonally driven response need greater study before scientists can fully appreciate how hormones impact behavior.