The caribou has the longest overland migration of any terrestrial mammal. In North America, some herds travel thousands of kilometres each year between wintering areas, summer ranges, and calving grounds.
The Porcupine caribou herd is a famous example. It moves between winter range in Alaska and Yukon and calving grounds near the Beaufort Sea, following seasonal food and snow conditions. Its annual route has been measured at more than 1,500 miles (about 2,400 kilometres), though other studies report even longer cumulative yearly movements for reindeer and caribou.
Caribou are members of the deer family Cervidae. They are unusual among deer because both males and females generally grow antlers. Their broad, flexible hooves help them cross tundra, snow, mud, and wet ground, while their diet includes lichens, grasses, sedges, and other tundra plants.
Pronghorn, moose, and elk also migrate, but their documented routes are generally shorter. “Reindeer” is the name commonly used for the same species in Eurasia; “caribou” is usual in North America.