Tundra rangelands of Alaska and northern Canada occupy about 200,000 and 900,000 square miles respectively. The tundra supports far lower numbers of large grazers than other natural areas, averaging less than 100 lb per square mile. Forage quality of tundra plants is high because of rapid growth and wide variation in seasonal progression of growth. The native grazers, caribou and muskoxen, have evolved rapid growth rates and selectively feed on the highest quality forage available. Wild populations of caribou and muskoxen appear to offer the best potential for conversion of tundra vegetation into commodities utilizable by man.