Caribou Herd

Caribou Migrate Farther Than Any Other Known Land Animal

Some herds of caribou migrate between 1,250 and 1,350 kilometers in Canada and Alaska each year to get from their wintering grounds to breeding grounds and back again.

Some animals really go the distance to find food, a mate or a place to raise their young. And now, thanks to scientists’ tracking efforts, we know just how far some land species will travel.

Using decades of scientific observations, researchers determined round-trip migration distances for a number of animals. Caribou have the longest migrations, with two different herds in Alaska and Canada traveling up to 1,350 kilometers per year, the team reports October 25 in Scientific Reports. That’s a little less than the distance from Los Angeles to Portland, Ore.

Gray wolves (Canis lupus) aren’t usually migratory, but a Canadian group thought to follow caribou is the only other tracked species that migrated over 1,000 kilometers in a year, the scientists found.

In the contiguous United States, mule deer (Odocoileus hemionus) have the longest annual land migrations, traveling up to 772 kilometers in Wyoming and Idaho. Other animals performing annual long-haul migrations — each around 600 to 700 kilometers round trip — include the blue wildebeest (Connochaetes taurinus) in the Serengeti of Africa, and the Mongolian gazelle (Procapra gutturosa) and Tibetan antelope (Pantholops hodgsonii) in Asia.

Pronghorn (Antilocapra americana) in Wyoming and Montana migrate about 300 kilometers, while pronghorns in Canada travel some 435 kilometers per year.

The researchers calculated the migration distances by measuring a straight line between the two migratory end points, and then doubling that for a round-trip figure. While the distances are impressive, they are still far short of the thousands of kilometers traveled each year by migrating insects (SN: 4/5/18) or birds (SN: 2/7/17), which can be less encumbered by infrastructure.

“For land animals, something as small as a road could be a barrier,” says Claire Teitelbaum, an ecologist at the University of Georgia in Athens who was not involved in this study. “A fence or wall certainly would be.”

Infrastructure, including roads and cities, already has hampered some animals’ land migrations, scientists say. And climate change could be having an effect by altering environments and the availability of foods, Teitelbaum says. Previous research had found that a herd of caribou (Rangifer tarandus) in Canada, for example, migrated up to 1,500 kilometers annually in the early 2000s when the herd had more members, instead of the current maximum of 1,350 kilometers. But it’s not clear exactly what caused that journey to be shortened.

Some caribou in Alaska and Canada have the longest annual migration route of any land animal, in part because these herds have lots of room to roam, a study finds. Gray wolves aren’t usually migratory, but a Canadian group thought to follow caribou is the only other tracked species that migrated over 1,000 kilometers in a year.

Only 7 percent of unbroken land patches worldwide are larger than 100 square kilometers, leading some scientists to predict shorter land migrations to come. “We will see migration distances declining, rather than increasing, into the future,” says Marlee Tucker, an ecologist at Radboud University in Nijmegen, Netherlands, who wasn’t involved with the work. “These [natural] areas are shrinking.”


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