Reindeer, also known as caribou in North America, shed their antlers annually. Unlike most other deer species where antler growth is limited to males, both male and female reindeer possess this ability. The process of growing and shedding these bony structures is an integral part of their yearly life cycle.
The Annual Antler Cycle
Antlers are bony outgrowths from a deer’s skull, fundamentally different from horns, which are permanent structures with a keratin sheath over a bony core. Reindeer grow new antlers each year from a base on their skull called the pedicle. The growth phase begins in spring, with antlers covered in a soft, vascularized skin known as velvet, which supplies blood and nutrients for rapid development. This velvet is rich in proteins, minerals, and growth factors, enabling antlers to be among the fastest-growing tissues in the animal kingdom.
As antlers reach their full size by late summer, the blood supply to the velvet diminishes, and it dries and sheds off. This process, often aided by rubbing against vegetation, reveals the hardened bone beneath. For mature male reindeer, antlers are fully developed for the autumn rutting season, where they are used for displays of strength and competition for mates. After the rut, in late fall or early winter, male reindeer shed their antlers.
Diverse Shedding Patterns
Both male and female reindeer grow and shed antlers annually. While male reindeer typically shed theirs after the mating season, from late November to mid-December, female reindeer exhibit a different shedding schedule. Pregnant females often retain their antlers throughout the winter, shedding them after calving in the spring, around May. This allows them to secure food resources by clearing snow, which is especially important during pregnancy.
Non-pregnant female reindeer and young reindeer may have varied shedding times, with some casting theirs during February. This distinct timing provides a competitive advantage for pregnant females, enabling them to access forage during the challenging winter months. The presence of antlers in both sexes, with their staggered shedding, highlights reindeer’s unique adaptations to their Arctic and subarctic environments.
The Purpose and Aftermath of Antler Shedding
Antler shedding is a hormonally regulated process, triggered by a decline in testosterone levels after the breeding season. This hormonal shift weakens the connection between the antler and the pedicle, leading to detachment. Shedding allows reindeer to conserve energy during the harsh winter, as carrying heavy antlers requires significant metabolic resources. It also ensures that a new, larger and stronger set of antlers can grow for the next mating season.
Once shed, reindeer antlers contribute to the ecosystem as a source of nutrients. Rodents, such as squirrels, mice, and porcupines, often gnaw on discarded antlers, consuming calcium, phosphorus, and other minerals. This consumption recycles essential minerals back into the environment. Shortly after shedding, the rapid regrowth process for the next year’s antlers begins.