© GaryAndJoanieMcGuffin.com / WWF-Canada
Same species, different stories
Getting the facts straight about caribou and reindeer
If you wanted to see a reindeer, your best bet might be to head to northern Scandinavia. But what if a caribou was on your bucket list? Are the two really that different? And what challenges are these deer-like animals facing in the Arctic? To answer these and other questions, The Circle spoke to JAN ADAMCZEWSKI, a former wildlife biologist with the Government of Northwest Territories in northern Canada. He’s been studying and working with caribou since the early 1980s.
Barren-ground caribou. © David McGeachy / WWF-Canada
What’s the difference between caribou and reindeer?
They both belong to the same species: Rangifer tarandus. But reindeer are found mainly in northern Europe and Siberia, where they exist both as wild herds and semi-domesticated animals that have been herded by people for thousands of years. Caribou are native to North America and remain wild. The word “caribou” describes wild populations in North America, while “reindeer” usually refers to the wild and semi-domesticated herds of Eurasia.
A main difference is that reindeer that are semi-domesticated are pretty tolerant of people, whereas wild caribou and wild reindeer are not. There are some semi-domesticated reindeer herds in Alaska as well as one in northern Canada.
There are several subspecies of caribou, such as: the Peary caribou, the smallest, palest caribou, found in the High Arctic islands of Canada, and the larger barren-ground caribou, found in the tundra regions and boreal forest of mainland Canada. We also know there have been many instances of caribou and reindeer interbreeding.
Boreal versus migratory tundra caribou
Caribou and reindeer are the same species even though their genetics, behaviours, appearances and habitats differ across their ranges. For the purposes of conservation and management in North America, they are divided into ecotypes that are based on habitats and behaviours rather than genetics.
Migratory tundra caribou roam the Arctic and sub-Arctic tundra in massive herds and undertake some of the longest land migrations on Earth—often covering thousands of kilometres each year. They are typically smaller and paler than other ecotypes, adapted for long-distance travel and endurance in extreme environments.
Boreal caribou, on the other hand, inhabit mature, lichen-rich boreal forests and are predominantly sedentary. They occur in small, isolated groups and generally migrate only short distances—about 50 to 150 kilometres annually. Physically, they are larger and darker, with broader, denser antlers and longer legs and heads than their tundra counterparts.
In Canada alone, experts recognize more than a dozen distinct caribou ecotypes—ranging from mountain caribou in British Columbia to the tiny Gaspésie herd in Québec—each with different habitats, behaviours and conservation challenges.
What traits do caribou and reindeer share?
Physically, they’re similar. Both are the only deer-like animal where the females have antlers. Caribou tend to be larger, with longer legs for migrations. The Peary caribou are the smallest of them—if you put one beside a barren-ground caribou, it would look almost like a calf. The Dolphin-Union caribou, a unique ecotype of barren-ground caribou named for its location in the western Arctic, is a little bigger than Peary caribou but smaller than barren-ground caribou. They have fairly big hooves, which helps with walking on snow and with swimming.
European reindeer have many of the same characteristics as caribou. Their body sizes vary somewhat, but fundamentally, these are all the same animal.
In the winter, most caribou and reindeer eat the same food: lichen, which can make up 80 to 90 per cent of their diet. Lichen is a moss-like substance made of a fungus and alga living together, often found on rocks and trees. When spring comes, they will eat less lichen and start eating different plants. They are very good at finding the plants and plant parts that have high nutrient contents. The mating season is usually in October, and pregnant females will typically give birth in May or early June. Normally, they will have one calf. But if the conditions are not so good—for example, if food is scarce, the winter has been harsh, or the effects of climate change have disrupted their migration or access to calving grounds—they may not breed every year.
Do all caribou and reindeer migrate?
No. European reindeer have seasonal migratory movements, but they don’t travel on the same scale as the migratory caribou herds of North America. In Siberia, wild reindeer do migrate—much like North American barren-ground caribou—while semi-domesticated reindeer often move with their herders instead of following long natural migrations. In both cases, calving grounds remain central, with females congregating there to give birth.
Jim Persson, Sámi reindeer herder. © Ola Jennersten / WWF-Sweden
How important are these animals to Indigenous Peoples?
It’s hard to exaggerate the importance of caribou—and the ability to hunt caribou—in Indigenous cultures across northern North America. There’s archaeological evidence showing that Indigenous People were hunting caribou as far back as 8,000 to 10,000 years ago. And there are Indigenous cultures that identify with caribou—not just as something to put on the table, but they identify as caribou people, culturally and spiritually. Hunting is very important for elders to pass on traditional knowledge and practices.
And the Sámi have been herding reindeer for many, many generations. This relationship differs from the caribou hunting cultures in North America, but there is a very close relationship between the people and their reindeer.
How is climate change affecting caribou and reindeer?
They’re a cold weather animal, so a warming climate is a major concern. Temperatures are warming faster at high latitudes, where caribou and reindeer are largely found. But climate is not having just one effect—there are many effects, some negative and some positive.
Spring tends to come earlier than it once did, which can mean that females that have just given birth and are nursing young calves have good access to green growth. But the vegetation is changing in some areas, with less lichen and more shrubs, which are harder to digest and less energy-rich. A warming climate also means that some parasites and pathogens can increase their range northward, which increases caribou’s and reindeer’s exposure.
Precipitation patterns are also changing—and one thing that’s really not good for these animals is warm winter temperatures followed by freezing. When you get a rain-on-snow event, the frozen ice crust that results locks the animals’ vegetation under ice. Freezing vegetation in winter has been associated with die-offs in Peary caribou and likely also affects other caribou and reindeer populations.
How the weather affects the insect season is also important. Historically, the insect season has been mostly confined to July. But these days, it can start in June and go well into August. The severity of the bug season is one of the major effects of warming weather on caribou. Caribou are vulnerable to biting flies, like black flies, mosquitoes and horseflies—and the ones that really seem to bother them are the warble and bot flies, which are parasitic. If the bugs are particularly bad, then instead of feeding and rebuilding their body reserves, the caribou will run around trying to get away from these pests. If the females don’t feed well in summer, then when breeding season arrives, they’re quite lean and less likely to be pregnant that winter.
Five decades of data
According to data collected since 1970, wild caribou and reindeer herds across the Arctic have shown dramatic swings in population over the past five decades.
While large fluctuations are natural, this Arctic herbivore has lost nearly two-thirds of its global abundance in the past three decades. Several of the largest North American herds, such as the Western Arctic and Bathurst herds, peaked in the 1980s and 1990s before declining sharply—for example, the Bathurst population fell from about 470,000 caribou in 1986 to fewer than 7,000 in 2022.
In contrast, the Porcupine herd has grown steadily, doubling from around 100,000 in the 1970s to more than 200,000 in recent years. Herds in Greenland have been relatively stable, while Siberian herds, such as the Taimyr, continue to rank among the world’s largest, despite having experienced a huge decline to currently only a quarter of its previous size.
Smaller herds everywhere remain vulnerable, with some numbering only a few thousand. Overall, the data highlight both the resilience and fragility of Arctic caribou in the face of changing conditions.
Woodland caribou, Canada. © GaryAndJoanieMcGuffin.com / WWF-Canada
What other threats are caribou and reindeer facing?
The threats that have become increasingly important in the last decades are human-caused: roads, seismic lines, mines and development in general. But it’s different for different herds. In the Canadian North, we generally have less development—so far—but there are lots of roads proposed. In the Northwest Territories, for instance, there is a winter road season to support active mines, and there is often a big truck coming every 30 seconds or so when this winter road season is running. As soon as you put in a road like that, you’re putting a barrier across the caribou’s range. We have already seen—from the ground and satellite collars on caribou—that caribou don’t cross those roads when the traffic is running at full speed. Roads can also make it much easier for hunters to find and hunt caribou and reindeer.
The fear is that the more roads and other infrastructure we build, the more we will inhibit their ability to move freely on the landscape.
—Jan Adamczewski, former Wildlife Biologist, the Government of Northwest Territories, northern Canada
We have known for some time that only migratory herds of caribou and reindeer are able to reach numbers in the tens and hundreds of thousands; migration allows them to avoid some of their predators, find the best forage seasonally, and avoid some parasites. Their migratory habit is what allows them to reach those big numbers. The fear is that the more roads and other infrastructure we build, the more we will inhibit their ability to move freely on the landscape—and somewhere along the line, that may mean smaller herds.
Are caribou and reindeer on the decline everywhere?
Sometimes one herd will be declining while a neighbouring herd is increasing in number. Since about 2000, most of the migratory herds in the Northwest Territories were either declining or at fairly low numbers. But over the last few years, a number of herds have stabilized—and some are actually growing at this point. So, each herd has its own conditions.
For example, there’s one herd called the Bluenose-East that has a calving ground in Nunavut, west of the community of Kugluktuk. From 2000 to 2018, this herd went through a major decline, from about 120,000 to about 19,000. But then from 2018 to 2021, it stabilized, and since then, it has actually shown quite an increase. So, after years of talking to people in nearby communities about limiting their harvest, it was wonderful to find that the herd is doing really well now.
What does the future hold for caribou and reindeer across the Arctic?
I think these are adaptable animals. They’ve persisted through all kinds of challenging climate conditions—even through the last ice age. In fact, the oldest caribou fossil known is something like 1.6 million years old. So I think they will be able to adapt as long as we don’t limit their ability to make whatever changes they need to survive. If we can really limit new development in key areas like calving grounds, including roads—and keep giving caribou the option to move freely on the landscape—then I think they’ll be able to adapt.
But if we start constraining their ability to move and change where they calve, then the likelihood of smaller herds increases. Ultimately, the healthiest caribou and reindeer are those with minimal human disturbance.
By WWF Global Arctic Programme
