Do bucks lose weight during the rut?
Yes — mature bucks routinely lose 20–30% of their pre-rut body weight by late November. A 220-pound October buck can be a 165-pound mid-December buck. The combination of reduced feeding, near-constant movement, and breeding effort burns body fat at a rate that's biologically expensive but necessary for breeding success.
Studies on whitetail body condition show fat reserves dropping fastest between roughly November 5 and November 25. Bucks rebuilding body condition heading into winter need a strong late-season food source to survive a cold winter — late-standing crops, oak mast, browse — which is why post-rut bucks pile on food sources by mid-December.
The practical implication: late-season hunts work because rut-depleted bucks need calories badly. Stand setups on standing corn, beans, or heavy browse near bedding can produce daylight bucks in December that you couldn't pattern in November.