Antlers are bony structures unique to the deer family (Cervidae), primarily found on male deer, known as bucks. They serve several biological purposes tied to the male reproductive cycle. However, female deer, or does, can rarely develop antlers. The reindeer (caribou) is a notable exception, as both males and females typically grow antlers.
Antlers: A Male Trait
Antlers are primarily a male characteristic, their development and annual cycle linked to the hormone testosterone. As daylight hours increase in spring, hormonal changes trigger the growth of antlers from bony projections on the skull called pedicles.
These antlers serve multiple functions for male deer, particularly during the breeding season (rut). They help establish dominance, compete for mates, and serve as visual displays of strength and genetic quality to attract females. The size and robustness of a buck’s antlers can signal its health and suitability as a mate. Their seasonal development equips bucks for these behaviors when reproduction is most active.
Rare Exceptions: Antlered Does
Although antlers are almost exclusively a male trait, female deer can rarely grow them. This phenomenon is estimated to occur in approximately 1 in 10,000 does. This is typically due to hormonal imbalances, often elevated testosterone, which can stem from issues with the ovaries, adrenal glands, or pedicle injuries.
Antlers on does often present differently from those on bucks. They are frequently smaller, unbranched, or malformed, and may remain covered in velvet rather than hardening and shedding. In some instances, does with antlers can still be fertile and reproduce.
The Antler Growth and Shedding Cycle
Antler development begins each spring from pedicles on the deer’s skull. During active growth, antlers are covered in velvet, a soft, vascular skin supplying blood and nutrients to the bone. Antlers are among the fastest-growing tissues in mammals, with some species adding up to one inch per day during peak growth.
As summer progresses, the antlers mineralize and harden, and the blood supply to the velvet diminishes. The velvet then dries and is rubbed off by the deer, revealing the polished, hardened antlers. After the breeding season, a drop in testosterone triggers antlers to shed, typically in late winter or early spring. Factors such as age, nutrition, and genetics significantly influence the size and form of antlers a deer develops each year.