The answer to whether female reindeer grow antlers is yes, making them a biological exception within the deer family. Reindeer, known scientifically as Rangifer tarandus, are the only cervid species where antler growth is a regular trait for both sexes. This unique adaptation is tied to the harsh, resource-scarce environments of the Arctic and subarctic regions where they live. The presence of antlers on the females is an evolutionary strategy that contributes directly to their survival and the success of their offspring.
Female Antlers: The Biological Fact
The antlers grown by female reindeer, often called cows, are noticeably different in size and structure compared to those of the males, or bulls. While a mature male’s antlers can be massive, sometimes exceeding 50 inches in length, a female’s pair typically grows to a more modest size, often reaching around 20 inches. The female antlers are thinner, lighter, and less branched, though they still develop the characteristic bony structure and are shed annually like those of the males.
This ability to grow antlers stems from a hormonal difference unique among female deer. Antler growth is stimulated by androgens, male sex hormones that includes testosterone. In most female cervids, estrogen and progesterone suppress this growth, but in female reindeer, the hormonal environment allows antler development to proceed. The antlers represent a substantial investment of energy and minerals, which is why their appearance and size often reflect the cow’s overall health and nutritional status.
Seasonal Timing of Antler Shedding
The most significant difference in antler biology between the sexes is the timing of the annual shedding cycle. Male reindeer shed their antlers relatively early, typically dropping them after the rut, or mating season, in the autumn months of November and early December. The male’s antlers have served their purpose for dominance displays and combat, and are then shed to conserve energy for the winter.
Pregnant females retain their antlers throughout the winter season, often not shedding them until May or June. This means that during the harshest months of the Arctic winter, the only adult reindeer with hard antlers are the pregnant females and young males. Non-pregnant females shed their antlers earlier in the winter, around February. The synchronized shedding around the time of calving ensures the mother is armed during the most vulnerable period of her reproductive cycle.
Antlers as Tools for Winter Survival
The retention of antlers through the winter provides female reindeer with an advantage for acquiring food. Their primary function during this period is to act as tools for “cratering,” or scraping away layers of hard-packed snow and ice to reach the vegetation underneath. This allows the pregnant cows to access winter forage, such as lichens, which are a source of energy to sustain both themselves and the developing fetus.
The antlers also function as a means of establishing a social hierarchy and asserting dominance, particularly over food sources. In the competitive environment of a winter feeding ground, pregnant females use their antlers to push away other reindeer, including the now antlerless adult males. This ensures they get priority access to forage, which is paramount to the successful gestation and birth of a healthy calf in the spring.
Reindeer’s Unique Place in the Deer Family
The reindeer’s biology sets it apart from all other members of the Cervidae family, which includes species like moose, elk, and white-tailed deer. In these other species, antler growth is strictly limited to the males. The presence of antlers on female reindeer is considered an evolutionary anomaly driven by the environmental pressures of the polar regions. The ability of the female to keep her hard antlers throughout her pregnancy ties her reproductive cycle directly to her survival needs. The reindeer is a singular example where the reproductive and survival advantages of female armament outweighed the energetic cost of growing and maintaining the bony structures.