BIO 203

Habitat and Geography

Grizzly bears live in mountainous regions throughout North America.  Female grizzly bears have a home range between 50 to 300 square miles and males have a home range between 200 to 500 square miles (U.S. Department of the Interior, 1995). Scientists have divided grizzly bear habitats into three different climatic zones.  Those zones are the alpine, subalpine, and temperate.  These zones are based on the altitudes at which grizzly bears live (Murray, 1995).

Alpine Zone

            The alpine zone of a mountain is the area above the tree line.  Once all of the snow has melted from the past winter, usually early summer, the alpine zone provides the bears with plants such as horsetail, grasses, spring beauty, and blueberries.  Most of the plants found in this zone are perennials and have adapted to a very short growing season.  They flower and disperse seeds in a very short amount of time during the summer.  Other plant species eaten by grizzly bears also begin to appear, as the days grow warmer.  Many other animal species such as moose, elk, deer, and small land mammals use the alpine zone during the summer months.  These animals like to use the alpine zone as birthing grounds so the bears have an easy meal if they stumble upon a newborn elk, deer, or moose (Murray, 1995).  These animal species are a main food source for grizzly bears, especially during the fall when grizzly bears are trying to gain as much fat as they can for their winter hibernation.  Recently, grizzly bears have been shown to use this zone more often than usual due to conflicts with humans (Stewart et. al., 2012).  In arctic areas, usually north of the Arctic Circle, grizzly bears spend their time year round in the alpine zone.  The alpine zone is a popular denning area for bears because of how hard some of the dens are to get to.  It provides security for the bears. (Murray, 1995).

Subalpine Zone

            The subalpine zone is an area that is dominated by thick forests and open clearings, belowSubalpine zone in Mt. Rainier National Park the alpine zone and above the temperate zone.  This zone is home to whitebark pine and subalpine fir groves.  This is a very cool and moist zone, which is perfect for growing blueberries, rasberries, blackberries, and huckleberries.  Another food source for bears in this zone is the nut of the whitebark pine.  Grizzly bears spend their time here in the summer and early fall months, mainly when berries are ripe.  There are also streams that run through this zone so the bears eat trout that call the streams their home.  Since this zone has a lot of thick forests, bears will tear apart rotten logs and eat the insects inside.  They will also eat elk, moose, and small mammals that live in the subalpine zone.  Any avalanche chutes in the subalpine zone make great denning areas for bears during the winter (Murray, 1995).

Temperate Zone

            The temperate zone is the zone you first see when you get close to mountainous regions.  It consists of lowland areas such as foothills and valley floors.  These areas are generally dry and have grassy vegetation, compared to the other two zones.  This zone also has woodlands and conifer groves.  Grizzly bears can be found in this zone from the early spring to late autumn.  Grizzly bears rarely ever hibernate in the temperate zone. Snow melts first in the temperate zone, providing some of the first food for bears as they begin to come out of hibernation.  Some food sources that are available in this zone are dead animals, small mammals, insects, grass, moose, elk, and roots of plants such as spring beauty and peavine.  This zone is also home to a lot of big rivers.  When the salmon run is in progress, you can find many bears next to these rivers gorging themselves on fresh salmon (Murray, 1995).

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