Lots of new or freshly renewed ground scrapes late in October do not signify a so-called “Peak of the Rut” is in progress. It only means cooler weather has finally caused highly aroused antlered bucks with new winter fur to begin a frenzy of marking individual breeding ranges. Does are not yet in heat at this time.
Each fall and early winter whitetails breed during three separate, two-week-long time periods. Estrus (heat) in does is triggered during these periods by a specific ratio of darkness to light (photoperiodism), occurring on the same exact dates in any one region annually. The first period generally occurs in November throughout the U.S. Some differences are seen in parts of Texas and Florida where this period occurs in October. The onset of each breeding period is progressively somewhat later from North to south in the U.S. In northern Minnesota where I hunt and study whitetails, breeding begins November 3rd annually.
At best, only about 10–12% of does are in heat on any one day throughout the two-week November breeding period, meaning, depending on deer densities only 1–2 of the usual 8-12 does capable of producing young per square-mile will be in heat on any one day (more in areas in which whitetails are over-populated or forced to congregate in remaining cover after deer-tall crops such as corn are harvested). Each doe will only be in heat 24-26 hours. During some days during this period, no does will be in heat within a specific square-mile. There should be little wonder, then, why it is so difficult to predict locations of mature breeding bucks while does are in heat.
Does not bred in November (about 15% for various reasons) will experience estrus again 28 days later and 28 days later again if still not bred, accounting for the second and third periods of annual breeding. In my Northern Minnesota study area, the second period of breeding begins December 1st. The third period begins December 28th, meaning, some breeding actually occurs well into January. My wife Jene and I have known and photographed several does that were always in heat on New Years Day.
The 85% of does bred during November give birth to 1–2 young in May. The 10% of does bred in December bear young in June. The remaining 5% bred in January and give birth to young in July (providing a means of determining which were bred during which time period).
“All of the above reveals there is no peak of the rut.” Just add the widespread notion there is one to the list of many strange beliefs American deer hunters continue to have about the whitetail rut (future blog posts).
Dr Nordberg on Deer Hunting 