Caribou are a large animal species found in the North American and Eurasian Arctic.

The Porcupine Caribou Herd ranges in northwestern North America. It's size depends on how many calves are born and survive and how many adult animals die during the year. Biologists believe that the recent declining trend in the 1990s is probably related to weather conditions (high snow accumulations on the wintering grounds and short summers in the early 90s).