The rut, the peak breeding season for white-tailed deer, is defined by intense hormonal shifts in bucks. This biological change fundamentally alters their priorities, causing a near-total cessation of normal feeding behavior. Driven by a surge of testosterone, the mature buck’s focus narrows to finding and breeding with receptive does. Consequently, a buck’s caloric intake drops drastically as reproductive success displaces nutritional maintenance as the primary biological directive.
The Biological Drive vs. Feeding
The lack of feeding during the rut results directly from the enormous physical demands and hormonal reprogramming of the buck. Increased testosterone levels trigger aggressive behavior and the single-minded pursuit of females, requiring immense energy output that leaves almost no time for grazing or browsing. Bucks spend time establishing dominance hierarchies, often involving strenuous fighting with rivals to secure breeding rights.
They are constantly active, traveling far outside their normal home ranges in search of receptive does. This includes activities like scent-checking trails and creating rubs on trees. This relentless movement and reproductive activity burns through the substantial fat reserves accumulated during the pre-rut period. The time commitment to these tasks is so complete that feeding becomes a negligible activity, replaced entirely by the drive to reproduce.
What Little Food Is Consumed
While bucks drastically reduce their food intake, they do not completely fast throughout the entire rutting period. They operate under a severe caloric deficit, engaging in “opportunistic feeding.” This means if a highly palatable, easily accessible food source is encountered incidentally, they may quickly grab a few mouthfuls.
This minimal consumption is neither strategic nor sustained, often occurring in brief windows near bedding areas or while tending a resting doe. They also seek out water sources for hydration, which is a necessity given the increased physical exertion and movement. The food consumed is typically high-energy browse that requires little effort to process. However, this intake is insufficient to meet the metabolic demands of their constant activity, forcing the buck’s body to rapidly metabolize stored fat and muscle tissue.
Immediate Post-Rut Nutritional Needs
The consequences of nearly fasting while maintaining high activity are severe, leading to physical exhaustion and significant weight loss once the rut concludes. Mature bucks commonly lose between 20 to 30 percent of their peak body weight during this intensive period. Their energy reserves are depleted, and their immune systems are often weakened due to the stress and caloric deficit.
Once testosterone levels decline, the buck’s biological priority immediately shifts from breeding to survival. They must rapidly rebuild body mass and fat reserves to survive the coming winter months. This recovery phase requires an immediate increase in the consumption of high-energy and high-protein foods. They seek out available food sources, such as late-season forages, agricultural remnants, or woody browse, to regain the strength necessary to withstand the cold and nutritional scarcity of late winter.