Color patterns among wolves in western North America

Pelt color of wolves (Canis lupus) is a highly visible characteristic that has been used in studies of taxonomy, and yet no comprehensive analysis of color variation in wolves has been conducted. We compiled observations from our wolf research, records from wildlife management agencies, and published accounts to document occurrence and distribution of pelt colors, and changes in individual wolves from black or gray to white. Less than 2% of wolves were white in North America. The proportion of white wolves increased northward from the taiga through the High Arctic of Canada and Greenland, where >90% of wolves were white or near white. Wolves that were white as pups probably remained white throughout adult life. Black wolves appeared to remain black or progressively changed to bluish-silver, silver, or white. Black wolves commonly had a white chest spot and white toes that faded with age. Gray-colored wolves may change to cream or white. Whitening among wolves may be influenced by 1) advancing age, 2) physiological stress, and 3) inheritance of genes that tend to be expressed as white.