Because whitetails are seasonal, short-day breeders, the timing of deer births is critically important for the species’ survival. Regardless of the environment, in the Northern hemisphere, whitetails are adapted to conceive at the proper time each autumn, so that fawns are born during spring (about 200 days later) when weather, food and cover conditions are favorable for maximum fawn survival.
Given the importance of this breeding/birthing schedule, reliable environmental cues are required to trigger the reproductive process in a timely fashion. Among whitetails, this cue is decreasing photoperiod — the ratio of daylight to darkness. Without fail, shortening periods of daylight in autumn cause physiological changes responsible for the whitetail’s breeding cycle.
If not for the infallible photoperiod cue, timing of the rut and fawn birth dates would fluctuate wildly…
