Grizzly bears (commonly known as brown bears) and gray wolves (also known as timber wolves) are capable of killing.

The grizzly bear, gray bear and even the black bear itself has been known to kill other black bears.

So, how do these black bears ward off their predators?

In areas where the geographic range of black bears overlaps that of either grizzlies or wolves, it would be adaptively strategic for black bears to resemble a grizzly bear in coloration.

Because grizzly bears are much larger and more aggressive than black bears, they have an advantage in an attack by another grizzly or a pack of wolves.

In fact, this is one of the hypotheses given for the evolution of non-black coloration in black bears.

A brown-phased black bear would better mimic the larger and more powerful grizzly bear, especially from a distance, compared to a black-phased black bear.

Furthermore, if a black bear were non-black in coloration, the probability of a potential fatal interaction with either a grizzly bear or a pack of gray wolves could be reduced.

In fact, pretend that a black-phased black bear is in a western state and a grizzly bear attacks it, what should it do? - it should stop pretending.

Support for this mimicry hypothesis makes some sense when we examine the historic distribution of grizzly and black bears. When Europeans colonized North America, grizzlies occupied much of the continent west of the Mississippi River, whereas black bears ranged widely throughout the continent.

If black bear populations evolved color patterns to mimic coexisting grizzly bear populations, we would expect a greater percentage of black bears west of the Mississippi to be non-black versus those east of the Mississippi.

Indeed, this is exactly what occurs when the percentage of black and non-black individuals is compared between eastern and western black bear populations.

For instance, brown or blonde coloration is found in about sixty-three percent of the black bears in Idaho and the northern Rockies, fifty-eight percent of the black bears in eastern Washington, and forty-six percent of the black bears in Arizona.

In marked contrast, adult black bears in the Midwestern and eastern states are virtually always black-phased.

Only about six percent of the black bears in Minnesota and one percent or less in mid-eastern states, -- for instance, New York, Pennsylvania, and West Virginia, have non-black bears. Most black bears born with non-black pelage east of the Mississippi River, as in Pennsylvania, eventually molt into a black phase by the age of two years.

Three additional reasons have been proposed to explain why there is a disproportionate percentage of black-phased black bears in eastern than in western states.

First, brush (early-successional) habitats in the eastern deciduous forest are typically characterized by dense vegetation, which are frequently used by black bears while searching for food, e.g., blackberries.

Some of us probably have encountered a black bear while berry picking in brushy thickets during summer in the East.

Based on studies of bird feathers containing the black pigmentation (melanin), as with common grackles, the fur of black-phased bears probably wears better in brushy habitats than brown or blonde pigmentation.

Second, bear habitats in western areas tend to be more 'open', with a lower density of trees, than those in the eastern United States.

Most observations of western black bears feeding during the midday in open habitats in the West are brown or blonde in coloration rather black in coloration.

This suggests that when the amount of solar radiation is highest, black-phased bears minimize heat stress by avoiding alpine meadows and open habitats.

Recall how hot the sun feels when you are wearing a dark-colored shirt compared to a light-colored shirt.

Finally, the percentage of non-black bears in the population may serve a camouflage purpose. In Arizona, black-phased black bears generally occur on cooler and wetter (i.e., darker) sides of mountains, whereas black bears with non-black coloration tend to be found on warmer and drier (i.e., lighter) sides of mountains.

This relationship between fur color and degree of aridity may enable these bears to better blend with the coloration of the local environment.