Why Do Deer Shed Their Antlers?

Deer shed their antlers as part of hormonal changes linked to their survival and mating season. In all but one species of deer, males carry antlers; in the reindeer (Rangifer tarandus), both sexes carry antlers. Antlers are not permanent appendages; they are shed and regrown annually. As the mating season, or rut, approaches, testosterone levels rise, leading to the growth of antlers. The growing antlers are encased in “velvet,” a highly vascularized, nerve-filled skin covered by short, soft hairs. Depending on the species, antlers take up to 150 days to grow, after which the velvet dies and is forcefully removed by rubbing the antlers against branches and small trees. Along with some blood residue, this imparts a brownish color to the otherwise white antler bone. Antlers finish growing before the mating season starts and are used as weapons and shields in combat or as display organs in courtship. Larger antlers are often seen as a sign of health and genetic fitness, making them more attractive to potential mates. Once the mating season concludes, testosterone levels drop, triggering the shedding of antlers. Some territorial tropical deer can retain their antlers for more than a year.

Growing antlers is an energy-intensive process that requires a significant amount of nutrients, particularly minerals and protein. By shedding their antlers after the mating season, deer can conserve their energy for survival during the harsh winter months.