AppearanceMost adult female grizzlies weigh 130–200 kilograms , while adult males weigh on average 180–360 kilograms . The average total length in this subspecies is 198 centimetres , with an average shoulder height of 102 centimetres and hindfoot length of 28 centimetres . Newborn bears may weigh less than 500 grams . In the Yukon River area, mature female grizzlies can weigh as little as 100 kilograms . On the other hand, an occasional huge male grizzly has been recorded which greatly exceeds ordinary size, with weights reported up to 680 kilograms . Although variable from blond to nearly black, grizzly bear fur is typically brown in color with white tips. A pronounced hump appears on their shoulders; the hump is a good way to distinguish a black bear from a grizzly bear, as black bears do not have this hump.
NamingThe word "grizzly" in its name refers to "grizzled" or grey hairs in its fur, but when naturalist George Ord formally named the bear in 1815, he misunderstood the word as "grisly", to produce its biological Latin specific or subspecific name "''horribilis''".
StatusThe grizzly bear is listed as threatened in the contiguous United States and endangered in parts of Canada. In May 2002, the Canadian Species at Risk Act listed the Prairie population of grizzly bears as being wiped out in Canada. As of 2002, grizzly bears were listed as Special Concern under the COSEWIC registry and considered threatened under the U.S. Fish and Wildlife Service.
Within the United States, the U.S. Fish and Wildlife Service concentrates its effort to restore grizzly bears in six recovery areas. These are Northern Continental Divide , Yellowstone , Cabinet-Yaak , Selway-Bitterroot , Selkirk , and North Cascades . The grizzly population in these areas is estimated at 750 in the Northern Continental Divide, 550 in Yellowstone, 40 in the Yaak portion of the Cabinet-Yaak, and 15 in the Cabinet portion , 105 in Selkirk region of Idaho, 10–20 in the North Cascades, and none currently in Selway-Bitterroots, although there have been sightings. These are estimates because bears move in and out of these areas, and it is therefore impossible to conduct a precise count. In the recovery areas that adjoin Canada, bears also move back and forth across the international boundary.
The U.S. Fish and Wildlife Service claims the Cabinet-Yaak and Selkirk areas are linked through British Columbia, a claim that is disputed.
All national parks, such as Banff National Park, Yellowstone and Grand Teton, and Theodore Roosevelt National Park have laws and regulations in place to protect the bears. Even so, grizzlies are not always safe in parks. In Glacier National Park in Montana and Banff National Park in Alberta, grizzlies are regularly killed by trains as the bears scavenge for grain that has leaked from poorly maintained grain cars. Road kills on park roads are another problem. The primary limiting factors for grizzly bears in Alberta and elsewhere are human-caused mortality, unmitigated road access, and habitat loss, alienation, and fragmentation. In the Central Rocky Mountains Ecosystem, most bears have died within a few hundred meters of roads and trails.
On 9 January 2006, the US Fish and Wildlife Service proposed to remove Yellowstone grizzlies from the list of threatened and protected species. In March 2007, the U.S. Fish and Wildlife Service "de-listed" the population, effectively removing Endangered Species Act protections for grizzlies in the Yellowstone National Park area. Several environmental organizations, including the NRDC, brought a lawsuit against the federal government to relist the grizzly bear. On September 22, 2009, U.S. District Judge Donald W. Molloy reinstated protection due to the decline of whitebark pine tree, whose nuts are a main source of food for the bears. In 1996 the International Union for Conservation of Nature moved the grizzly bear to "Lower Risk Least Concern" status on the IUCN Red List.
Farther north, in Alberta, Canada, intense DNA hair-snagging studies on 2000 showed the grizzly population to be increasing faster than what it was formerly believed to be, and Alberta Sustainable Resource Development calculated a population of 841 bears. In 2002, the Endangered Species Conservation Committee recommended that the Alberta grizzly bear population be designated as threatened due to recent estimates of grizzly bear mortality rates that indicated the population was in decline. A recovery plan released by the Provincial government in March 2008 indicated the grizzly population is lower than previously believed. The Provincial government has so far resisted efforts to designate its declining population of about 700 grizzlies as endangered.
Environment Canada consider the grizzly bear to a "special concern" species, as it is particularly sensitive to human activities and natural threats. In Alberta and British Columbia, the species is considered to be at risk. In 2008, it was estimated there were 16,014 grizzly bears in the British Columbia population, which was lower than previously estimated due to refinements in the population model.
The Mexican grizzly bear is extinct.Conservation efforts have become an increasingly vital investment over recent decades, as population numbers have dramatically declined. Establishment of parks and protected areas are one of the main focuses currently being tackled to help reestablish the low grizzly bear population in British Columbia. One example of these efforts is the Khutzeymateen Grizzly Bear Sanctuary located along the north coast of British Columbia; at 44,300 hectares in size, it is composed of key habitat for this threatened species. Regulations such as limited public access, as well as a strict no hunting policy, have enabled this location to be a safe haven for local grizzlies in the area. When choosing the location of a park focused on grizzly bear conservation, factors such as habitat quality and connectivity to other habitat patches are considered.
The Refuge for Endangered Wildlife located on Grouse Mountain in Vancouver is an example of a different type of conservation effort for the diminishing grizzly bear population. The refuge is a five-acre terrain which has functioned as a home for two orphaned grizzly bears since 2001. The purpose of this refuge is to provide awareness and education to the public about grizzly bears, as well as providing an area for research and observation of this secluded species.
Another factor currently being taken into consideration when designing conservation plans for future generations are anthropogenic barriers in the form of urban development and roads. These elements are acting as obstacles, causing fragmentation of the remaining grizzly bear population habitat and prevention of gene flow between subpopulations . This, in turn, is creating a decline in genetic diversity, and therefore the overall fitness of the general population is lowered. In light of these issues, conservation plans often include migration corridors by way of long strips of "park forest" to connect less developed areas, or by way of tunnels and overpasses over busy roads. Using GPS collar tracking, scientists can study whether or not these efforts are actually making a positive contribution towards resolving the problem. To date, most corridors are found to be infrequently used, and thus genetic isolation is currently occurring, which can result in inbreeding and therefore an increased frequency of deleterious genes through genetic drift. Current data suggest female grizzly bears are disproportionately less likely than males to use these corridors, which can prevent mate access and decrease the number of offspring.
ReproductionGrizzly bears have one of the lowest reproductive rates of all terrestrial mammals in North America. This is due to numerous ecological factors. Grizzly bears do not reach sexual maturity until they are at least five years old. Once mated with a male in the summer, the female delays embryo implantation until hibernation, during which miscarriage can occur if the female does not receive the proper nutrients and caloric intake. On average, females produce two cubs in a litter and the mother cares for the cubs for up to two years, during which the mother will not mate. Once the young leave or are killed, females may not produce another litter for three or more years, depending on environmental conditions. Male grizzly bears have large territories, up to 4,000 square kilometres , making finding a female scent difficult in such low population densities.
Grizzlies are subject to population fragmentation, which tends to reduce the population by causing inbreeding depression.
FoodAlthough grizzlies are of the order Carnivora and have the digestive system of carnivores, they are normally omnivores, since their diet consists of both plants and animals. They have been known to prey on large mammals, when available, such as moose, deer, sheep, elk, bison, caribou, and even black bears. Grizzly bears feed on fish such as salmon, trout, and bass, and those with access to a more protein-enriched diet in coastal areas potentially grow larger than interior individuals. Grizzly bears also readily scavenge food on carrion left behind by other animals.
Canadian or Alaskan grizzlies are larger than those that reside in the American Rocky Mountains. This is due, in part, to the richness of their diet. In Yellowstone National Park in the United States, the grizzly bear's diet consists mostly of whitebark pine nuts, tubers, grasses, various rodents, army cutworm moths and scavenged carcasses. None of these, however, match the fat content of the salmon available in Alaska and British Columbia.
Although the diet of grizzly bears varies extensively based on seasonal and regional changes, plants make up a large portion of their diet, with some estimates as high as 80–90%. Various berries constitute an important food source when they are available. These can include blueberries , blackberries , salmon berries , cranberries , buffalo berries , and huckleberries , depending on the environment. Insects such as ladybugs, ants and bees are eaten if they are available in large quantities. In Yellowstone National Park, it has been observed that grizzly bears may obtain half of their yearly caloric needs by feeding on Miller moths that congregate on mountain slopes. When food is abundant, grizzly bears will feed in groups. For example, many grizzly bears will visit meadows right after there has been an avalanche or glacier slide. This is due to an influx of legumes, such as ''Hedysarum'', which the grizzlies consume in massive amounts. When food sources become scarcer, however, they separate once again.
In preparation for winter, bears can gain approximately 400 lb , during a period of hyperphagia, before going into false hibernation. The bear often waits for a substantial snowstorm before it enters its den: such behaviour lessens the chances that predators will find the den. The dens are typically at elevations above 1,800 metres on north-facing slopes. There is some debate amongst professionals as to whether grizzly bears technically hibernate: much of this debate revolves around body temperature and the ability of the bears to move around during hibernation on occasion. Grizzly bears can "partially" recycle their body wastes during this period. In some areas where food is plentiful year round, grizzly bears skip hibernation altogether.Trophy hunting causes an imbalance between the male and female sexes, since older males are primarily sought to be hunted for their size. The hunting of older males creates a gender imbalance within an area specific population. The killing of older male bears in their own territory allows other males to migrate in and claim the late bear's territory. Older male bears will have had cubs with existing female bears in the region. This may cause the newly migrated male bear to become potentially infanticidal towards cubs of the resident females and the late male bear.
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