Grizzly Bear Habitat

For all living species, food, water, secure places to rest, and adequate physical space to occupy are the essential elements of habitat. The current state of habitat in relation to grizzly bears is somewhat artificial. Grizzly bears are capable of living in some habitats (such as the Great Plains) that they no longer occupy because their presence is incompatible with agriculture and human civilization.

In the lower forty-eight states, grizzly bears primarily roam across alpine and subalpine forests. They occupy similar habitat in the mountains of western Canada and Alaska. Where bears are present along the Pacific coast of Alaska and Canada, they’re often found near streams where they prey upon fish, primarily spawning salmon. At the northernmost portions of their range, in Alaska, the Yukon, Northwest Territories, and Nunavut, grizzly bears make their living in the open tundra.

The amount of space required as habitat for individual grizzly bears varies remarkably depending upon their gender and the geographic area in which they live. Whether it’s Grand Teton National Park in Wyoming or Katmai National Park in Alaska or any other location occupied by bears, male grizzlies require much more space than females. The average home range of a boar is two to ten times larger than that of a mature sow living in the same area. Scientists believe the larger ranges of males are related to two primary factors. First, a larger space gives a male higher odds of finding and mating with females. Second, the larger body size of males necessitates a higher protein and caloric intake to maintain, requiring males to range over a more expansive area in search of food. It is important to remember that grizzly bears technically occupy a home range, not a territory. In biological terms a “territory” refers to a segment of land occupied by an animal where other animals of the same species or gender are expelled. Grizzly bears are not territorial in this sense. The range of several males and females may overlap, even though individual bears have preferred areas.

Just how large is a grizzly bear’s home range? One research study involving twelve female bears on Admiralty Island, Alaska, showed an average size of slightly more than 9 square miles. Another study that recorded the movements of nineteen male bears in the central Northwest Territories of Canada yielded an average home range occupying just over 3,150 square miles, a land area significantly larger than the state of Delaware. Individual grizzly bear males in the open tundra of north-central Canada are believed to have ranges as large as 10,000 square miles, an area 100 miles wide by 100 miles long, or slightly larger than the state of Vermont. A grizzly bear’s home range is highly correlated to forage. Bears occupying areas with access to abundant, high-quality food sources (such as salmon) have much smaller ranges than those living in areas where forage is less plentiful.

Grizzly bear females, with or without cubs, require a smaller home range than males.

GRIZZLY ISSUES

Habitat Fragmentation

Grizzly bears thrive in large tracts of wilderness or roadless habitat where they’re buffered from routine disturbance by humans and their vehicles. However, such areas are the exception, not the rule, in the contiguous United States and much of southwestern Canada. Furthermore, regions of wilderness habitat are often “islands” surrounded by private land or public lands where human activities such as logging, mining, and agriculture abound.

In such areas habitats that could potentially support grizzly bears are isolated from one another. Known as “habitat fragmentation” in biological circles, this phenomenon affects not only grizzly bears but other creatures such as lynx, wolverines, and bighorn sheep. Habitat fragmentation makes it difficult for grizzly bears to expand their range through the natural process of species dispersion as one region of habitat reaches its “carrying capacity.” Young bears, incapable of claiming a territory in the area of their birth, are prime candidates to move into unpopulated regions. However, if such movement requires navigating a course across roads, through river valleys occupied by agriculture or areas of high human population, the odds of a young bear making it to another area of unoccupied habitat are severely diminished. Thus, preserving habitat for grizzly bears not only includes managing a suitable amount of land area for the bears, it also means ensuring that sufficiently wild “corridors” connect larger chunks of habitat to avoid fragmentation.

Roads fragment grizzly bear habitat and sometimes create impediments to the dispersal of young adult bears seeking new territories.