Which epic journey came first: Santa Claus’s annual, Christmas Eve circumnavigation of the globe or the grandiose, yearly “reindeer” migration? Scientists say we now have the answer.

Just five days from now, the magic will happen. Santa Claus will step into his gift-laden, reindeer-powered sleigh and make his annual, around-the-world trip.

The character of Santa Claus was originally inspired by the fourth-century, Greek bishop Saint Nicholas of Myra in Asia Minor (now Turkey), a man renowned for his generosity and kindness. One of the most popular tales about him involves his anonymously dropping a bag of gold down the chimney of a house that belonged to three impoverished sisters, who had no money for dowries. The gold pieces landed in the stockings that the women had hung near the fireplace to dry.

But a story that’s even older than Santa Claus himself involves his four-footed helpers, the reindeer, also known as caribou. According to a new study from researchers at the University of Cincinnati, caribou have been using the same Arctic calving grounds for more than 3,000 years. And that’s at least 1,200 years before Santa ever set up his shop at the North Pole.

Caribou are members of the deer family. In the fall, mature males have a striking white neck and mane. Their colors are more faded during the winter. ©Menno Schaefer/

Caribou commutations

According to the National Park Service, caribou and reindeer are the same species and share the same scientific name, Rangifer tarandus. “Caribou” are what the animals are called in North America, and “reindeer” are what they are known as in Eurasia. Such reindeer live mostly in Scandinavia and Siberia, and they are typically smaller with shorter legs than their wild caribou relatives.

All caribou are wild animals, whereas reindeer can be wild, semidomesticated or domesticated (animals selectively bred with a specific purpose in mind). Though there are generalized, visual similarities between caribou and reindeer, their appearance can vary from individual to individual, as it is influenced by diet, environment and, in the case of reindeer, selective breeding.

Caribou are native to Alaska. While there are many subspecies of caribou throughout the world, the barren-ground subspecies (Rangifer tarandus granti) dominates Alaska.


Caribou and reindeer are the same species. All caribou are wild animals, but not all reindeer are. Reindeer can be wild, semidomesticated or domesticated.

Barren-ground caribou undertake nature’s longest overland migration, traveling as far as 800 miles each year to reach their spring calving grounds in the Arctic National Wildlife Refuge and Canada’s Ivvavik National Park. The largest herd in this area, named for the Porcupine River, numbers in the hundreds of thousands.

Scientists think caribou use these areas as calving grounds because they have fewer predators and offer seasonal vegetation near places where the caribou can avoid the worst of the mosquitoes, which can do significant damage to a young calf.

Female caribou shed their antlers within days of giving birth, leaving behind a physical record of their annual, epic travels across Alaska and Canada’s Yukon that may persist on the cold tundra for hundreds of years.


Barren-ground caribou make nature’s longest overland migration, traveling almost 800 miles each spring to reach their calving grounds in the Arctic National Wildlife Refuge. The Porcupine Herd, the largest in the area, numbers in the hundreds of thousands.

Caribou conveyor belts

Caribou antlers, like those of deer, elk and moose, are made of fast-growing bone that the animals shed each year and regrow the following year. Knowing that bones dropped by animals that lived dozens of generations ago can provide meaningful information, scientists from the University of Alaska Fairbanks, the University of Cincinnati, and the U.S. Fish and Wildlife Service decided to collect shed antlers for isotopic analysis.

But finding antlers in the vast expanse of the Arctic National Wildlife Refuge required meticulous logistical planning. Small planes deposited the researchers and their gear deep in Interior Alaska, where they had to be watchful for grizzly and polar bears. Using rafts to navigate remote rivers, they conducted grid searches of suitable caribou habitat identified in advance using aerial photography. The scientists walked back and forth, searching for antlers along old river terraces, covering every inch of the area in order to find the “ancient treasures” exposed on the tundra.

And find them, they did. Amazingly, they recovered antlers that have sat undisturbed on the Arctic tundra since the Bronze Age; some of them turned out to be 3,000 years old. The results of this study were published in the journal Frontiers in Ecology and Evolution in February 2023.

AdobeStock (Created by Candice Gaukel Andrews)

This sun-bleached, barren-ground caribou skull with antlers was found in shrubbery on the tundra in Canada’s Northwest Territories.

While male caribou antlers span four feet and weigh more than 20 pounds, those of females are much smaller (less than two feet). Both, however, contain nutrients—such as calcium and phosphorus—that are important to animals and plants. The dropped antlers also create “nutrient sinks,” which could have a profound effect on an area’s vegetation.

In fact, the caribou migration may serve as a nutrient “conveyor belt” that draws caribou back to reap the benefits of their “antler fertilizer” in a reinforcement loop. Caribou and other mammals are known to chew on dropped antlers for their valuable minerals. This could be an important dietary supplement for new caribou moms.

Caribou consciousness-raising

The researchers report that walking around the landscape of the Arctic National Wildlife Refuge and picking up something that’s 3,000 years old was mind-blowing. Typically, to find that kind of ecological history, one would have to dig deep down into the soil. But on the Coastal Plain, vegetation grows extremely slowly. One of the awestruck scientists noted that the oldest of the antlers that they found while conducting the study would have been growing at approximately the same time that Homer was penning The Iliad and The Odyssey.

For more than 3,000 years, generations of caribou have made the same epic journey. ©Martin Capek/

This study demonstrates how important the caribou calving grounds are for animals that native Alaskans and Canadians still depend on for sustenance, even as energy companies seek to exploit gas and oil resources in this protected area. Luckily, in 2023, the Biden Administration suspended drilling leases in the Arctic National Wildlife Refuge, the largest tract of undeveloped wilderness in the United States—and in what we now know has been an important area for caribou for millennia.

Unfortunately, though, the Arctic is warming faster than other parts of the globe. Sections of the Arctic that were once barren tundra are now sprouting new spruce forests. The scientists state that this summer they were in Arctic Village, Alaska, located just south of the caribou calving grounds, and they talked with Native American elders about the changes that they have seen. They said that where once they looked at large stretches of open, barren ground, there were now tracts full of trees. They asked, “What will happen to the barren-ground caribou as this habitat gets converted into forests?”

I think we should all be asking that question, because it gets at the heart of why we should care about this landscape, even if we’ll never see it.


In the Arctic, areas that were once tundra are now turning into forests. What will happen to the barren-ground caribou as this habitat continues to rapidly change?

Santa’s caribou crew

There’s an interesting sidenote about Santa and his much-anticipated sleigh journey: while female caribou drop their antlers after giving birth in the spring, males don’t drop theirs until after the fall mating season, around November. While we don’t know exactly why, it’s thought that the males’ huge antlers might be most important for competition with other males during the mating season but could be a significant drawback for survival over the winter. The advantages of antlers for females are to use them for protection against wolves—their primary predator when they are pregnant—and to safeguard their spring newborns. Females also use their antlers to brush away winter snow when searching for food.

Given the December 24 date of Santa’s Christmas ride, then, all the male reindeer would have dropped their antlers. That means that the pictures of Dasher, Dancer and the rest of the gang hitched to Santa’s sleigh—with antlers held high—are images of an all-female team.

Happy holidays, and here’s to finding your true places and natural habitats,