The reindeer (also known as a caribou) is a member of the deer family, native to the tundra, boreal forests, and mountains of the extreme frigid north. In human culture, it is a staple of northern mythology and art, a motif adorning coats of arms, and an important part of the Christmas tradition. The names reindeer and caribou are largely interchangeable, but depending on where you live, there may be different naming conventions. In Europe and Asia, these animals are always called reindeer, but in North America, they’re called caribou in their wild habitat and reindeer when domesticated.
There are 14 recognized subspecies in the wild, plus two extinct subspecies, each of which has its own distinctive appearance and location. Population numbers appear to be declining in some places due to human activity, including climate change and the loss of boreal forests; it is currently classified as a vulnerable species by the IUCN Red List, at least in the wild.
Antlers are the largest and most prominent feature of the deer family. These are big branching bones that grow from the top of the head. Some people may accidentally mistake them for horns, but the major difference is that horns are made from a different substance called keratin, which is also found in hair and nails. The other major difference is that antlers undergo an annual cycle of shedding and growth, whereas horns are normally kept for the animal’s entire lifespan (though the pronghorn is an exception).
The Life Cycle of an Antler
This process of growth begins around February when the first antler nubs will emerge from the top of the head. During the spring and early summer, they will grow around half an inch per day, curving backward along the head and forming a kind of C shape. The summer months also herald many other distinctive changes to the reindeer’s anatomy, including a browner coat, gold-colored eyes, and softer hooves. At the same time, the antlers start to grow a soft but thick velvety fur, which contains an immense surplus of tiny blood vessels and nerves to help facilitate growth even further.
This velvet will remain on the antlers for the next few months until the antlers have reached their maximum size. Starting around the first week of August, the reindeers will strip or rub off the velvet layer from the antlers, leaving behind the hard and sharp bone in preparation for the mating season in October and November. The scientific term for this period of sexual excitement is a rut. The males use their big antlers to compete with each other for access to mates during the rut. This clash of strength is done by locking antlers together and trying to push the other deer out of the way. The weaker male will usually cede the contest, thus giving up his access to the mates. The largest and most dominant males can gather anywhere between five and 15 females during a single season.
When the rut is finally complete, the reindeer will start shedding its antlers again in November or December. This is accompanied by several other anatomical changes, including the growth of a white winter coat, harder hooves to break through the ice and forage for vegetation, and a transformation of the iris color from gold to blue. The males will have completely shed all antlers by the end of the year.
Antler Size and Sexual Differences
While antlers are primarily a male instrument, reindeer are the only members of the deer family in which females are able to grow antlers as well. The sexes can be distinguished from each other by the size and shape of their antlers. Male antlers grow more branching points and measure anywhere between 39 inches and 53 inches in beam length, whereas the female antlers only measure about 20 inches and generally have a simpler structure.
Another important difference is that females tend to retain their antlers long after the mating season, only shedding them until they’ve produced calves sometime in the spring. The size of the female antlers may help to determine same-sex hierarchy and access to preferential feeding grounds in the winter. This is particularly important during pregnancy, which requires a considerable amount of food intake to sustain. With better access to food, the healthiest females with the largest antlers are more likely to produce viable offspring. Consequently, in places where food is more abundant, reindeer do not compete as much for resources. Antlers suddenly become a costly encumbrance, because they require energy to grow.
The size of the antlers in both sexes reflects both the nutritional intake of the reindeer (making it a useful proxy for overall health) and climate variations in the surrounding environment. But what’s perhaps even more interesting is that the reindeer antlers are the largest, in comparison to the overall body size, of all deer species. They are so large, weighing up to 33 pounds, that reindeers need large neck muscles and big heads to support them.
Reindeer will grow their antlers for the first time at a very early age before they even reach puberty at around the age of two. The size and complexity of the antlers increase every year and then remain relatively fixed from the age of five onward. The annual development of the antlers is at least partially controlled by hormones. This ensures they reach their maximum size just in time for the reproductive season in the late fall. If you change the production of sexual hormones, then you can change the size and shape of the antlers. This can be observed in the fact that castrated males have similar antler cycles as females.
Human Uses for Reindeer Antlers
Reindeer are an important part of many northern indigenous cultures, including the Sami people of northern Sweden and the Inuit of North America, which traditionally use them for their milk, fur, meat, and blood, as well as a means of transportation. Reindeer antlers can be fashioned into all kinds of tools, including knife handles, shovels, and drying racks. Each part of the antler seems to have its own particular use in some cultures. This tradition has carried on for many thousands of years, helping humans to survive in otherwise difficult northern conditions. Reindeer have been semi-domesticated to make it even easier to access their resources. They are the only domesticated deer species in the world.