Seasonality: Hormones and Behavior

Seasonal environmental change in all regions of the world affects vertebrate endocrinology and behavior. In temperate and arctic regions, vertebrates often principally detect and respond to annual changes in day length. In tropical regions that do not experience significant seasonal changes in day length, other seasonal environmental factors, such as rainfall, food supply and/or presence of conspecifics, drive hormonal status and behaviors. Here, we review the major endocrine systems underlying seasonal expression of behaviors and use notable examples to illustrate the vast diversity of hormones, physiologies, and behaviors influenced by seasonality of the environment.