Deer are part of the Cervidae family that include moose, reindeer, elk and other species. Here are some fun facts about deer.
* The whitetail deer mating season, or rut, is influenced by the amount of daylight, a phenomenon known as photoperiodism.
* Hormones like melatonin, which are regulated by light, play a key role in triggering reproductive behaviors in deer.
* The Harvest Moon, the full moon closest to the Autumn Equinox, is a significant natural trigger for these hormonal changes.
* Based on lunar cycles, the 2025 whitetail rut is predicted to peak in early to mid-November.
As archers begin their whitetail season in New York state on Oct. 1, 2025, they will be hunting under the Harvest Moon, which is full Oct. 6 this year.
Normally, the Harvest Moon is in September, and those of us who follow such things may wonder if the full moon closest to the Autumn equinox, occurring in October, will have any bearing on the iconic Whitetail Rut?
This year's Harvest Moon is what is termed by astronomers and astrologers as a "Super Moon," brighter and closer to the earth than usual, due to its elliptical orbit.
And incidentally, it is the first Full Moon in a triad of three Super Moons, the next rising in early November, a week after Halloween, and the third in early December, timed for what we call the second rut. Then a varying percentage of doe fawns of the year, plus older doe that didn't conceive in the first go-around, cycle.
Whitetails and others are termed "short-day breeders."
Along with deer, sheep, and elk, all are tuned by photoperiodism, a big word for the amount of light. And as the days shorten with less light, these animals undergo tremendous biochemical hormonal changes affecting their reproductive behaviors.
Changing light affects deer in various ways. In bucks, it is most notable from the growth of antlers to the shedding of velvet, to finally dropping or shedding the antler itself.
The Harvest Moon is particularly significant because it is always named as the Full Moon closest to the Autumn Equinox (this year occurring Sept. 22). This year, the Corn Moon, which occurred Sept. 7, was very close to being the Harvest Moon, as the two full moons are almost equal in time from the Autumn equinox.
When the moons phase the same, on the same dates (Metonic cycle) every 19 years, my notes show the rut to peak in the same window. By going back and checking my spreadsheet detailing the 2006 and 1987 hunting seasons, the forecast is for an early to mid-November rut. A classic rut, intense and exciting, unlike last season's trickle rut.
The Autumn Equinox is one of two days each year when daylight and the darkness of nighttime are of equal length. The other is the Vernal Equinox which signals the beginning of spring in March, dramatically changing the amount and timing of hormones like testosterone and melatonin, to name two.
Sheep breeders as well as ranchers who raise deer are very aware of the effect of melatonin on the timing of the breeding cycle of their respective animals because they buy melatonin implants.
In order to have all their ewes drop their lambs in the spring (or does drop fawns) at the same time, melatonin implants, suppositories, are used as a manmade biochemical trigger like the Harvest Moon in wild deer.
Melatonin, a complex hormone found in many animals and plants, helps set circadian rhythms, or life cycle responses such as reproduction, sleep and blood flow. A small gland in the brain behind the optic nerve called the pineal gland generates melatonin.
When the deer or sheep farmer withdraws the melatonin implant, the hormones dissipate from the ewe or in the case of farm-raised deer, in the doe, and then breeding can occur.
The bright Harvest Moon along with decreasing daylight acts in the same was as do melatonin implants, or CIDRs (Controlled Internal Drug Release) used by the deer and sheep farmers, as light stimulates melatonin flow.
But as the moon begins to quickly wane, the shorting days and ever-increasing darkness help the dissipation of melatonin in wild whitetails.
Much research is being done on another tiny but important hormone regulatory gland, the Suprachiasmatic Nucleus (perfectly positioned on the Optic nerve chiasm). Through the influence of light it governs the flow of melatonin created in the pineal gland.
Whitetails will have their biological clocks set by this amazing Harvest Moon and the equinox. And one month later, the annual whitetail rut peaks during the first and second week of November this year.
Bow hunters may especially hope that October's full moon, a week after Halloween this year, will have added significance in being called 2025's Harvest Moon.
-- Oak Duke writes a biweekly Outdoors column.