Understanding Caribou Migration: More Than Just a Seasonal Journey

When we think about migration, we typically think of birds flying south for the winter. Other animals, such as some species of caribou, also migrate. Unlike birds, which are primarily avoiding harsh winter weather and temperatures, caribou migrate for a variety of reasons.

Why do these fascinating ungulates hit the open road? Where do they go and how many caribou typically migrate all at once? Here is everything you need to know about caribou and their migration patterns.

What Are Caribou?

If the term caribou is unfamiliar to you, perhaps their other name is more familiar. They are also known as reindeer, which almost certainly explains why the lichen they feast on in winter is referred to as reindeer moss.

These animals live about 15 years and weigh up to 700 pounds. It is an unfortunate truth that, despite their high population numbers, their survival is potentially threatened by Arctic drilling. While some species appear to be thriving, others are considered endangered and at risk of going extinct.

Why Do Caribou Migrate?

One reason caribou migrate is to reach remote birthing grounds. This is to protect their newborns from predation. Golden eagles, wolves, and grizzly bears target calves during their most vulnerable early days.

Another reason for their travel is to reach northern ice fields, thereby staying away from mosquitos that would otherwise plague them in warmer months. They return south when the weather grows colder. Migration also allows them to avoid overgrazing specific areas and gives the animals the ability to eat whatever food is growing most abundantly in each season.

The vast herds of migrating caribou also perform an essential function for the lands they inhabit. As they move, they graze down grasses and shrubs, fertilizing and aerating the ground. This process regenerates and protects grasslands and tundra, which, in turn, supports a vast array of other wildlife. The migration of herds has always been a critical element in maintaining the amazing fertility of our open land.

Caribou Herd Facts: How Many Caribou Migrate?

The largest caribou herd is the Western Arctic Herd. At its peak, this herd consisted of nearly 500,000 animals and still has numbers close to 260,000. Its migration territory covers over 150,000 square miles of Alaska, an area larger than the whole state of California.

Perhaps the best known of the migrating caribou herds is that of the Porcupine Caribou in Alaska. They are located primarily within the Arctic National Wildlife Refuge and named for the river they migrate along. There are nearly 200,000 of them, crossing the Alaska refuge and parts of the Northwest Territories and the Yukon in Canada.

Scientists use a radio tracker collar on select members of the herd, as well as low altitude photography to follow their migration patterns each year. These trackers have taught biologists a lot about the traveling habits of these intriguing creatures.

Scientists take a herd census every three years, weather and conditions permitting. This lets them know whether herd populations are rising or falling and whether migration patterns have changed significantly from the prior census.

When Do Caribou Migrate and How Far?

The typical caribou migration route begins in spring, during April. Pregnant cows and the rest of the herd trek nearly 400 miles toward the herd’s specific birthing fields. Located on the Arctic coastal plain for the Porcupine herd, it’s common for only maternal cows to make the full journey into the calving grounds. Males and non-maternal females stay on the outskirts of the grounds until migration begins again.

The next leg of their migrating journey begins in summer, during late June or early July. To avoid being endlessly bitten by mosquitoes, the herd heads north. They will only stay there a few weeks before they start heading back south, toward wherever they plan to spend the fall and winter. This varies from year to year. In total, their trek across the map takes them close to 800 miles.