Sex steroids modulate circadian behavioral rhythms in captive animals, but does this matter in the wild?

Nearly all organisms alter physiological and behavioral activities across the twenty-four-hour day. Endogenous timekeeping mechanisms, which are responsive to environmental internal cues, allow anticipate predictable changes time their daily activities. Among-individual variation in chronotype, or phenotypic output of these mechanisms (i.e. timing behaviors), is often observed studied under naturalistic conditions. The neuroendocrine system, including sex steroids, has been implicated regulation modulation endogenous clocks outputs. Numerous studies have found clear evidence that steroids modulate circadian captive animals controlled However, little known about how influence rhythms wild what, if any, implication this may for survival reproductive fitness. Here we review vertebrates We then discuss relationship be relevant success fitness limited organisms.