Few animals inspire more in the human psyche than the grizzly bear. At once loved and despised, revered and feared, the grizzly bear simultaneously fulfills the role of nurturing spirit and nemesis, for human beings. There is perhaps no greater symbol of wilderness than the grizzly bear, and, indeed, where the grizzly survives in viable populations it is a general sign of the integrity of that ecosystem. Despite its image of ferocity and strength, the grizzly bear's place in the ecosystem sits in a fine balance and is intolerant of much disturbance. This, combined with a slow reproductive rate linked to very high maternal investment, means that the loss of just one or two bears, or an ecological disturbance resulting in habitat marginalisation, can result in serious population reduction or even regional extinction. There are many places that we see as wilderness, because they are devoid of the structures we associate with developed areas, but the levels of disturbance or human activity in them may mean that grizzly bears no longer exist there. Their absence is the first sign of wilderness status having been lost, and, like the keystone of a bridge being removed and the whole structure collapsing afterwards, so the interactions of the other species in an ecosystem are disrupted by the loss of the grizzly bear.
The grizzly (brown) bear was apparently named by early European explorers and settlers in North America because of a combination of the appearance of its coat, and character traits they observed in its behaviour (grisly)! The grizzly bear ranges today from the Yellowstone ecosystem in north-west Wyoming to the northern coast of Alaska and Canada's Yukon and Northwest Territories. While brown bears in general are omnivores, the Kodiak bear is largely carniverous, and the grizzly bear, is about 90% herbivorous. All bears are opportunist feeders, and much of the 10% of meat in the grizzly bear's diet, is comprised of carrion. The lower protein, more herbivorous diet of the interior or mountain grizzly means that it is significantly smaller than its Alaskan coastal cousin or the Kodiak.
The grizzly bear was originally an animal of the Great Plains, but it may have begun a retreat to the west when the Plains Indians began to use horses for hunting. It was then pushed out of the plains and into the mountains by the westward advance of European settlers in North America, in the 18th and 19th Centuries. As recently as the early 1920's grizzly bears still existed as far south as California and Arizona, populating every western state of the continental United States between there and the Canadian border. In only 80 years since, however, the exponential growth of the human population in the west, and all its attendant development, has reduced this range to a contiguous area encompassing Montana from the Rocky Mountains west, and northern Idaho. Technically separated from this, the Greater Yellowstone Ecosystem still supports a good population of grizzly bears. Otherwise, the only grizzly bears remaining south of Canada are in the North Cascades of Washington State.
Grizzly bears mate between May and July, while implantation of eggs into the uterus is delayed until October or November. The total gestation period is between 180 and 266 days, with the cubs being born between January and March, when the mother is hibernating. Cubs generally stay with their mother for two years, although they will stay for three or four if the sow does not become pregnant in the fall of their second year. Pregnancy triggers a reaction in the sow through which she drives the cubs off and hibernates on her own in preparation for giving birth to new cubs the following spring. Cubs will often spend their first hibernation together, and three-year olds observed in frequent close proximity in the spring are most likely to be siblings who have denned together. Female grizzly bears become sexually mature at between 4 and 6 years old, though growth continues later than that, while first pregnancies occur on average between the ages of 5 * and 7.
Grizzly bears are extremely good mothers, and, consistent with the high level of 'investment' they make in their cubs to ensure their survival, they are very protective of them. Because of this, encountering a grizzly bear, indeed any bear, with young can be very dangerous. During the first two years of their lives, the sow will teach her cubs everything they need to know to survive on their own. She will literally school them in finding and exploiting different food sources, and the cubs spend significant time observing her actions and learning them for themselves. This can be very clearly seen in footage from McNeil Falls or Brooks Camp, in Alaska, where cubs will sit watching their mother catch fish. Because this high level of input is critical if cubs are to survive on their own after separation from their mother, it is easy to understand why cubs that lose their mother in their first year are severely disadvantaged. Many bears that become what we term 'nuisance' animals as adults, were orphaned as cubs and as a result did not learn all they needed to from their mother. Because bears are adaptable and intelligent, many that are classed as nuisance animals are in fact improvising on what is available for their survival. If one considers that many cubs lose their mothers due to human action or negligence, it seems doubly hard on the bear that it should then be dealt with as a nuisance or 'problem' bear for adapting to its surroundings in the absence of its mother's teaching.
Interestingly, while adult grizzly bears do not climb trees, cubs can; sows may tree their cubs as a defensive measure. Grizzly bears have long straight nails for digging, that are not good for climbing, though it has been argued that there is no need for the grizzly bear to climb as, technically, no other animal preys on it. Black bears, which do climb, have short, curled nails that are better suited to climbing. The polar bear has similar nails to the black bear, though in it's case, they are designed for gripping on the ice, when running or climbing out of water, and for tearing apart prey.
A grizzly bear boar may weight 700lbs, averaging perhaps 350-500lbs, while a healthy, mature adult male would not generally be much lower than 350-400lbs. A large sow could weigh 500lbs, though mature females might average between 300-400lbs. By comparison, an Alaskan coastal grizzly bear boar could weigh between 800-1200 pounds, and a female could range between 600-800lbs. Male Kodiak bears can weigh as much as 2000lbs, though an average weight for mature animals would be between 1200-1500lbs. A female Kodiak might weigh 1000lbs, though an average adult weight might be around 700lbs.
One of the characteristics that separates bears from dogs is the ability to 'free' stand on their rear legs, a trait that allows them a better view of their surroundings. An adult male grizzly bear may stand at 7-9 feet tall, while a female may reach 6-8 feet. A male Alaskan coastal grizzly might be between 9-10 feet while a Kodiak bear could reach 11 feet. Kodiak bears may, in extreme cases reach up to 13 feet, but an average height for a mature male would be nearer 11 feet. Females might reach 9-10 feet.
Grizzly bears begin hibernation in the fall, between October and December, with pregnant females being the first to do so, and males the last. They are not true hibernators, but, rather, go into a state of torpor in which their metabolic rate is significantly reduced. They may wake from this, periodically, and, on some occasions, they may leave the den for a while to look for food. The hibernation period is correspondingly less in the southern reaches of the range. Grizzly bears generally dig their own dens, which are normally located on sheltered alpine slopes, and make a bed out of dry vegetation. They may use a particular den repeatedly. A bear of 700lbs may come out of hibernation at 450-400lbs, while a bear of 350-400lbs might come out of hibernation at 250-200lbs. A large female of 500lbs, that was breeding, might come out of the den at 200lbs, while smaller breeding females entering the den at 350-400lbs can deplete to a little as 150lbs. Males will come out of hibernation first, sometimes appearing as early as February, though on average the hibernation period ends between April and May.
Grizzly bears have a potential lifespan of about 30 years in the wild, although in reality few live that long. Bears that range in any close proximity to a human population all to often fall victim to hunting, traffic, or being killed because of a conflict or nuisance situation. In the wild, older bears, past their prime, can be killed by younger animals during the mating season, or, exceptionally, if they were very weak, they could be killed by wolves. Unfortunately, grizzly bears, like black bears, rarely reach their potential longevity in the wild now, in a world where they are constantly under pressure from human encroachment and development.
In the wilderness is the salvation of the world.
Henry David Thoreau