Distribution and Analysis of Colourmorphs of the Black Bear (Ursus americanus)

Records on colour and location of >40,000 black bears (Ursus americanus) were gathered from the United States and Canada. Corollary information on subspecies, sex, age, year, habitat and past or present association with grizzly bears (Ursus arctos) was available for >11,000 black bears. Information was collated into regional groups and black or non-black categories, locations were mapped and isochromes drawn, and corollary data analysed with chi-square, discriminant function, and log-linear analyses. Most bears in eastern North America are black, with random occurrence or small enclaves of non-black colourmorphs. Non--black individuals constitute a progressively higher percentage of populations from east to west across Ontario and the Great Lakes states, and account for 5-10% of populations in western Ontario and Minnesota. Colourmorph ratios in western North America vary from predominantly black to predominantly non-black. Black colourmorphs occur most fre- quently in dense boreal and northern montane forests and temperate rain forests. The percentage of black individuals in populations decreases from north to south in the Rocky Mountain region and from the Pacific Coast inland. Non-black bears are more common in open forests on the lower slopes of the northern and central Rocky Mountains, in the interior moun- tains of California, and in the desert ranges of the southwestern United States. Patterns are repeated in geographically and floristically distinct, but physiognomically similar, habitats. Chi-square, discriminant function and log-linear analyses indicate that subspecies, habitat and association with grizzly bears are related to colour ratios in populations. When the variable subspecies was controlled analytically, both results and inter- pretation of distributional information suggested that colouration is more cryptic than mimetic in black bears.