Timing of the whitetail rut is determined by photoperiod — the ratio of daylight to darkness. The diminishing amount of daylight in autumn triggers physiological changes responsible for the whitetail’s breeding cycle.
On Northern range, unlike in the South, this “breeding window” is narrow and assures maximum fawn survival, because fawns are born during spring when food and cover are plentiful. In turn, this produces a predator “swamping effect,” meaning predators are overwhelmed with potential prey, and a higher percentage of fawns survive.
Other factors, most notably nutrition and social behavior, also come into play to determine precisely when — or if — an individual doe enters estrus, breeds and conceives young.
Interestingly, on Northern range, the length of the whitetail rut is chiefly governed by the onset of winter…
