On Father’s Day, hundreds of thousands of people across the United States will show appreciation for the love, encouragement, and support that their fathers have provided them throughout their lifetimes. Interestingly, numerous animals provide parental care to their offspring, from fish and birds to non-human primates and humans. Yet, there is substantial evidence that many species must juggle parental care with another social behavior that is essential for reproductive success and survival: aggression.
Over twenty-five years ago, field endocrinologist John Wingfield and colleagues proposed the Challenge Hypothesis based on data acquired from seasonally-breeding male birds. The Challenge Hypothesis posits that seasonal changes in the secretion of testosterone (T) — a steroid hormone produced by the gonads that facilitates reproduction and its associated social behaviors — are the result of a trade-off between the extent of parental care that an individual provides and the amount of competition that individual faces in their environment. (more…)