Species like white-tailed deer enter "rut" as daylight fades.
High melatonin levels stimulate the release of Gonadotropin-Releasing Hormone (GnRH). short day breeders
: Breeds in tropical regions may cycle year-round because day length remains relatively constant, whereas those in temperate or northern latitudes show more defined seasonal patterns . The Biological Mechanism Species like white-tailed deer enter "rut" as daylight fades
Here are the key features of (animals that breed when day length is short, typically in autumn/winter): short day breeders
Regulation of Seasonal Reproduction by Hypothalamic ... - PMC
Photoperiodism is the physiological reaction of organisms to the length of night or day. In short-day breeders, the primary trigger is the increase in melatonin production.