Alaska is the only state in the United States where three distinct species of North American bears reside: the Brown/Grizzly Bear, the North American Black Bear, and the Polar Bear. This vast landscape, ranging from temperate rainforests to the Arctic tundra, supports these diverse populations. Understanding the distinctions between these species requires examining their physical features and the specific habitats they occupy across the state.
Defining Brown Bears and Grizzly Bears
Brown bears and grizzly bears are regional names for the same species, Ursus arctos, differentiated primarily by geography and diet. Coastal bears, often called brown bears, have access to abundant, high-protein food sources like spawning salmon. This rich diet allows them to grow significantly larger, with some males reaching weights over 1,000 pounds.
Inland bears, typically called grizzlies, inhabit the state’s interior, including the tundra and mountains. These grizzlies rely on a more varied and less concentrated diet of roots, berries, vegetation, and small rodents. Consequently, they tend to be smaller than their coastal cousins.
Both types share defining physical characteristics, including a prominent shoulder hump composed of muscle and fat above their front legs. This hump serves as an anchor for powerful digging motions. Their front claws are long, relatively straight, and light-colored, adapted for excavating dens and foraging. They also possess a distinctly “dished” or concave facial profile, with small, rounded ears set far back on the head.
North American Black Bears in Alaska
The North American Black Bear (Ursus americanus) is the most widespread bear species across the continent, occupying most of Alaska’s forested areas. Despite the name, black bears in Alaska exhibit significant color variation, ranging from jet black to dark brown and cinnamon hues.
Black bears are generally smaller than brown bears, and their physical structure is adapted for climbing trees. They lack the prominent shoulder hump, giving their backs a more level appearance. Their claws are shorter, darker, and more sharply curved, providing excellent grip for scaling tree trunks.
The facial profile of the black bear is notably straight from the forehead to the nose, contrasting with the dished profile of the brown bear. They also have larger, more prominent, and oval-shaped ears. Although widespread throughout the state’s forests, black bears are absent from the Alaska Peninsula south of Lake Iliamna and the islands of the Kodiak Archipelago.
Polar Bears The Arctic Marine Mammal
The Polar Bear (Ursus maritimus) is a highly specialized species found along Alaska’s northern and western coasts, bordering the Arctic Ocean and the Bering Sea. They are classified as marine mammals due to their reliance on the marine environment for survival. Polar bears spend much of their lives on the sea ice, using it as a platform to hunt their primary prey: seals.
Their diet consists almost exclusively of ringed and bearded seals, consuming the blubber to maintain massive fat reserves. To survive the frigid Arctic environment, they have unique adaptations, including a thick layer of blubber and a dense coat of fur. Their skin is black to absorb solar radiation, and their white fur provides camouflage against the snow and ice.
Polar bears are built more streamlined than brown bears, lacking the pronounced shoulder hump and possessing a longer neck and narrower skull. Their range is directly tied to the presence of stable sea ice, which is necessary for their hunting strategy. This dependence makes them vulnerable to the ongoing loss of sea ice.
Identifying Bears in the Field
Distinguishing between Alaska’s three bear species requires focusing on specific anatomical features rather than relying on size or color. The most reliable indicator is the presence or absence of the shoulder hump: the Brown/Grizzly Bear is the only species with this prominent muscular mass. Black Bears and Polar Bears possess a flatter profile along their backs.
The shape of the ears and facial profile are also key. Brown/Grizzly Bears have small, rounded ears paired with a distinctively dished face. Black Bears have larger, more prominent, oval-shaped ears, and their face presents a straight profile.
Finally, examine the claws. Brown/Grizzly Bears have long, straighter claws designed for digging, while Black Bears have shorter, sharply curved claws that aid in climbing trees. Polar Bears are easily identifiable by their white coloration, extremely large paws, and exclusive presence in the northern sea ice environment.