Circannual rhythms

Circannual rhythms have evolved as genetically programmed adaptive timing mechanisms to allow organisms use favorable seasons to reproduce and grow, and survive through unfavorable seasons. These govern seasonal changes in the physiology and behavior, and hence optimize offspring survival by coordinating reproductive efforts at the best-suited time of the year, and overall fitness in the periodic world. Here, we define and describe formal properties and synchronization of circannual rhythms, provide several examples of circannual rhythm mediated seasonal events, and discuss putative mechanisms and recent advances in elucidating the mechanism(s) of circannual timing in birds and mammals.