The peak mating season for ungulates, commonly called the rut, is a period of activity driven by hormonal changes in both bucks and does. For white-tailed deer, this initial wave of breeding is synchronized across a geographic area, creating movement and competition. This major breeding event does not mean every female is successfully bred during that short window.
Not all does enter their receptive period simultaneously, and some may not conceive during the initial attempt. A subset of the female population will become receptive again later in the season. The recycling of these unbred does results in a subsequent, smaller spike in breeding activity known as the second rut. This secondary period ensures the highest possible reproductive success for the herd.
The Biological Basis of the Secondary Estrous Cycle
The cause of the second rut lies in the reproductive physiology of the white-tailed doe, which is polyestrous. This means the female can experience multiple periods of estrus, or heat, within a single breeding season if conception does not occur. The initial breeding season is triggered primarily by the photoperiod—the steady decline in daylight hours as autumn progresses. This change signals the doe’s body to begin the reproductive cycle.
The estrous cycle in a white-tailed doe averages approximately 28 days (ranging from 21 to 30 days). If a doe is not successfully bred, or if a fertilized egg fails to implant, her hormonal levels reset. She will then re-enter estrus approximately four weeks after her first cycle. This predictable interval drives the secondary breeding wave, providing a second opportunity to conceive.
Female fawns may also contribute to this second wave if they reach a body weight threshold due to high-quality nutrition. These young females are often not mature enough to cycle during the primary rut, but they may enter their first estrous period later in the season. The presence of these late-cycling fawns contributes to renewed breeding interest from bucks during the secondary rut.
Calculating the Timing of the Second Rut
Determining the start of the second rut is a calculation based on the timing of the initial peak breeding activity. Because the doe’s estrous cycle is consistently about 28 days, the secondary rut occurs roughly four weeks after the peak of the primary rut. This calculation is more reliable than using environmental variables like temperature, snow, or moon phase, which do not govern the doe’s hormonal cycle.
In many regions of the northern United States, the primary rut peaks during the first two weeks of November. Applying the 28-day interval places the secondary rut peak in the first or second week of December. If the primary rut peaks later, such as around Thanksgiving, the secondary rut will be pushed into the latter half of December.
The peak breeding window varies significantly across geographic locations, making local knowledge of the primary rut timing essential. In northern latitudes, the rut is compressed and consistent. However, in southern states, the peak can be highly variable, sometimes occurring from late September through mid-February. The most accurate method for predicting the secondary rut is to identify the historical peak breeding date for a local deer herd and add 28 days.
The secondary rut is not a single day but a period of renewed activity leading up to the calculated peak. It usually begins a few days before the 28-day mark and continues for about a week afterward. This window allows for the highest concentration of receptive unbred does and late-cycling fawns, prompting bucks to begin actively searching again.
Distinct Behavioral Indicators
The second rut is characterized by observable signs, though the intensity is lower than the widespread activity of the primary rut. Bucks recovered from the main breeding period move with renewed focus, seeking the smaller number of receptive does. This means bucks are often seen traveling widely across their home range.
A clear physical indicator is the reactivation of traditional signposts, such as scrapes and rubs, which went dormant after the primary peak. Bucks will freshen these scrapes, pawing the ground and marking them with scent to advertise their presence to late-cycling females. This renewed marking behavior confirms bucks are actively engaging in breeding movements.
Chasing behavior is also a strong indicator, though it is less frantic and widespread than pursuits seen during the primary rut. Bucks will be observed closely tending to and pursuing the few does in estrus, often concentrating movements around localized groups of females. This focused attention can draw other bucks, leading to localized competition.
An increased number of younger bucks, including yearlings, may participate, as the dominance hierarchy is less strictly enforced when fewer does are available. Mature bucks remain the primary drivers of breeding, and their heightened movement patterns during daylight hours confirm the secondary rut is underway.