Wednesday, June 8, 2011

Brown Bear Species South of Canada

Grizzly-brown bear-Ursus arctos

Although wildlife management concepts were formed nearly 100 years ago, bears and their management have
been poorly understood. Recent concern for the environment, species preservation, and ecosystem management are only now starting to affect the way we manage grizzly/brown bears . Indeed, the difficulty in understanding brown bear biology, behavior, and ecology may have precluded sufficient change to prevent the ultimate loss of the species south of Canada. Grizzly/brown bears must be managed at the ecosystem level. The size of their ranges and their need for safe corridors between habitat units bring them into increasing conflict with people, and there seems to be little guarantee that people will sufficiently limit their activities and landuse patterns to reduce brown bear damage rates and the consequent need for damage control. Drastic changes may be needed in land-use management, zoning, wilderness designation, timber harvest, mining, real estate development, and range management to preserve the species and still meet damage control needs.

Grizzly/brown bear, Ursus arctos

 The brown bears of the world include numerous subspecies in Asia, Europe, and North America. Even the polar bear, taxonomically, may be a white phase of the brown bear. Support for this concept is provided by new electrophoresic studies and the fact that offspring of brown/polar bear crosses are fertile. The interior grizzly (Ursus arctos horribilis) is generally smaller than the coastal (Ursus arctos gyas) or island (Ursus arctos middendorffi) subspecies of North American brown bear, and it has the classic “grizzled” hair tips.

Brown bears in general are very large and heavily built. Male brown bears are almost twice the weight of females. They walk with a plantigrade gait (but can walk upright on their hind legs), and have long claws for digging (black  bears and polar bears have sharper, shorter claws). The males can weigh up to 2,000 pounds (900 kg), but grizzly males are normally around 400 to 600 pounds (200 to 300 kg). Wherever brown bears live, their size is influenced by their subspecies status, food supply, and length of the feeding season. Bone growth continues through the sixth year, so subadult nutrition often dictates their size potential.

Brown bears are typically brown in color, but vary from pure white to black, with coastal brown bears andKodiak bears generally lighter, even blond or beige. The interior grizzly bears are typically a dark, chocolate brown or black, with pronounced silver tips on the guard hairs. This coloration often gives them a silvery sheen or halo. They lack the neck ruff of the coastal bears, and grizzlies may even have light bands before and behind the front legs. Some particularly grizzled interior brown bears have a spectacled facial pattern similar to that of the panda or spectacled bears of Asia and South America.

Brown Bear

White grizzlies (not albinos) are also found in portions of Alberta and Montana, and in south-central British
Columbia. Such white brown bears may be genetically identical to the polar bear, but so far electrophoresic
studies have not been completed to determine the degree of relatedness. The interior grizzly’s “hump,” an
adaptation to their digging lifestyle, is seen less in the coastal brown bears, polar bears, or black bears. The brown bears (including the grizzly) are also characterized by their high eye profile, dish-shaped face, and short, thick ears.

The brown bears of North America have lost considerable range, and are currently restricted to western Canada, Alaska, and the northwestern United States . Their populations are considered secure in Canada and
Alaska, but have declined significantly in the lower 48 states. Before settlement, 100,000 brown bears may have  ranged south of Canada onto the Great Plains along stream systems such as the Missouri River, and in isolated, small mountain ranges such as the Black Hills of South Dakota. They were scattered rather thinly in Mexico and in the southwestern United States, but may have numbered about 10,000 in California, occupying the broad, rich valleys as well as the mountains.

Coastal Brown Bear Sleeping

Grizzly/brown bear habitat is considerably varied. Brown bears may occupy areas of 100 to 150 square
miles (140 to 210 km2), including desert and prairie as well as forest and alpine extremes. The areas must provide enough food during the 5 to 7 months in which they feed to meet their protein, energy, and other nutritional requirements for reproduction, breeding, and denning. They often travel long distances to reach seasonally abundant food sources such as salmon streams, burned areas with large berry crops, and lush lowlands. Denning habitats may be a limiting factor in brown bear survival.

Grizzly bears seek and use denning areas only at high elevations (above 6,000 feet [1,800 m]), where there are deep soils for digging, steep slopes, vegetative cover for roof support, and isolation from other bears or people. Since grizzlies select and build their dens in late September, when their sensitivity to danger is still very high, even minor disturbances may deter the bears from using the best sites. Unfortunately, the habitat types bears choose in September are scarce, and human recreational use of the same high-elevation areas is increasing.

Food gathering is a top priority in the life of grizzly/brown bears. They feed extensively on both vegetation and animal matter. Their claws and front leg muscles are remarkably well adapted to digging for roots, tubers,
and corms. They may also dig to capture ground squirrels, marmots, and pocket gophers. Brown bears are
strongly attracted to succulent forbs, sedges, and grasses. In spring and early summer they may ingest up to 90 pounds (40 kg) of this high-protein forage per day. Brown Bears gain their fat reserves to endure the 5- to 7- month denning period by feeding on highenergy mast (berries, pine nuts) or salmon. The 2 1/2- to 3-month summer feeding period is particularly crucial for reaching maximum body frame and preparing for the breeding season and winter.

Being ultimate opportunists, brown bears feed on many other food items. For example, the Yellowstone grizzlies have clearly become more predatory since the closure of the garbage dumps in the Yellowstone area. They are exploiting the abundant elk and bison populations that have built up within the park. They hunt the elk calves in the spring, and some bears learn to hunt adult elk, moose, and even bison. The ungulate herds, domestic sheep, and cows also provide an abundant carrion supply each spring the animals that die over winter thaw out just when the bears need a rich food source.


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