Last Updated on Wednesday, 02 June 2010 14:33

Common Name: Grizzly Bear
Also referred to as: Brown Bear, Kodiak Bear
Genus species: Ursus arctos
Recognized subspecies: Ursus arctos horribilis Ord, Ursus arctos middendorffi Merriam, Ursus arctos dalli Merriam
Family: Ursidae
Order: Carnivora

General Description:

• Weight: Males: 145 to 357 kg; Females: 98 to 226 kg.
• Shoulder height: approximately 1.4 m.
• Grizzly Bears are sexually dimorphic, with the males being up to 2 times larger than females.
• Large hump of muscle over the scapulae.
• Fur is generally brown, but may range in colour from blonde to nearly black.
• Guard hairs are often silver tipped, giving the bear a “grizzled” appearance.
• Long front claws up to 10 cm.
• Dental formula: I 3/3 C 1/1 P4/4 M 2/3. Bunodont dentition.
• Compared to the Black Bear, Grizzly Bears are larger in body size, have a dish-shaped face, as well as longer claws and smaller ears.

North American Distribution:

• Current Range is drastically reduced from the historical range and includes Alaska, Yukon, Northwest Territories, Nunavut, south to British Columbia, Alberta, Montana, Wyoming, and Idaho.
• In the lower 48 states of the United States, the Grizzly Bear has been extirpated from 98% of its original range. It has also been extirpated from the prairie and boreal plains in Manitoba, Saskatchewan, and Alberta.
• Historical range once extended eastward to Ontario, Ohio, and Kentucky and southward to Mexico. In the north, the range may have extended as far as Labrador.

Habitat Description:

• Grizzly Bear habitat selection occurs at a variety of spatial scales.
• Throughout their North American range, Grizzly Bears use a wide range of seasonal habitats. In mountainous areas, Grizzly Bear habitats include avalanche chutes, riparian areas, coniferous subalpine forests, and moist meadows. In plateau and foothill landscapes, Grizzly Bears use mature Lodgepole pine forests and regenerating clearcuts.
• Home range size corresponds to sex and the concentration of quality food sources. Males have larger home ranges.
• Female home range size may range from 24 to 2400 km2. Male home ranges may vary from 115 to 8000 km2.
• Grizzly Bears prefer areas that are remote and have minimal human disturbance.

Movements and Migratory Habits:

• Grizzly Bears travel throughout their home range in search of concentrations of high quality seasonal food sources.
• Typically, Grizzly Bears will use lower elevations in early spring and summer, while higher elevations are used in late spring and fall.
• Most Grizzly Bears will excavate their own den into sloping ground or under the base of trees. However, some bears will also use natural openings, such as caves or hollow trees, for the winter denning period, which may last from several weeks to 7 months. During this time, the bears are in a state known as winter lethargy.
• Grizzly Bears are not true hibernators, as their body temperature does not drop significantly and they can be aroused almost instantly.
• While in their dens, these bears do not eat, drink, defecate, or urinate.
• During this time, females are able to support fetal development and lactation. The young are born mid-winter while in the den.
• Food availability, weather conditions, and sex and age class are the main factors in determining timing of den entry.
• Pregnant females are the first to enter dens.

Diet and Foraging Strategy:

• Grizzly Bears are opportunistic omnivores.
• Main seasonal food items include herbaceous vegetation, such as grasses, sedges, and horsetails during spring and berry-producing shrubs (e.g., Vaccinium spp, Shepherdia canadensis) during summer. A variety of forbs, roots, bulbs, as well as insects (e.g., ants, moths), small mammals (e.g., marmots) and fish can also be consumed throughout the spring, summer, and fall seasons. Whitebark pine nuts, which provide a rich energy source, are also consumed in the Greater Yellowstone Ecosystem, as well as Waterton Lakes and Glacier National Parks.
• Adults require animal matter in their diet to maintain large size.
• Populations in Alaska and British Columbia often feed on spawning salmon.
• Ungulates and calves of ungulates are occasionally preyed upon or eaten as carrion. Often feed on winter-killed ungulates at spring emergence.

Reproduction:

• Grizzly Bears are polygamous, and both sexes generally mate with several individuals.
• A litter may have the offspring of more than one male.
• Mating occurs from May to July.
• Gestation is 229 to 266 days. Grizzly Bears display embryonic diapauses, with implantation occurring in late November.
• Females give birth to litters of 1 to 3 cubs.
• Young are born around February.
• Interval between litters is 3 years, on average.
• Females reach sexual maturity at 3.5 years old, and males at 5.5 years old.

Conservation Status:

• Federal:
  • Prairie Population: Extirpated
  • Northwestern Population: Special Concern
• Provincial: May Be at Risk