Meriwether Lewis and William Clark first described it as grisley

The Grizzly Bear is a large population of the Brown Bear inhabiting North America. Scientists generally do not use the name grizzly bear but call it the North American Brown Bear.  Subspecies include:

Grizzly SilhouetteKodiak
Peninsular Grizzly
California Grizzly (now extinct)
Mexican Grizzly
Black Grizzly

The Meaning of “grizzly”

Meriwether Lewis and William Clark first described it as grisley, which could be interpreted as either “grizzly” (i.e., “grizzled”—that is, with golden and grey tips of the hair) or “grisly” (“fear-inspiring”, now usually “gruesome”).  The modern spelling supposes the former meaning; even so, naturalist George Ord formally classified it in 1815 as U. horribilis, not for its hair, but for its character.

Grizzly Bear Size and Appearance

Black vs GrizMost adult female grizzlies weigh 290–400 lb, while adult males weigh on average 400–790 lb. Average total length in this subspecies is 6.50 ft, with an average shoulder height of 102 cm (3.35 ft) and hind foot length of 11 in.  Newborn bears may weigh less than 1.1 lb. In the Yukon River area, mature female grizzlies can weigh as little as 220 lb. One study found that the average weight for an inland male grizzly was around 600 lb and the average weight for a coastal male was around 900 lb. For a female, these average weights would be 300 lb inland and 500 lb coastal, respectively.  On the other hand, an occasional huge male grizzly has been recorded which greatly exceeds ordinary size, with weights reported up to 1,500 lb.  A large coastal male of this size may stand up to 9.8 ft tall on its hind legs and be up to 4.9 ft at the shoulder.

Grizzly claws are longer than an American black bear's and adapted for digging
Grizzly claws are longer than an American black bear’s and adapted for digging

Although variable in color from blond to nearly black, grizzly bear fur is typically brown with darker legs and commonly white or blond tipped fur on the flank and back.  A pronounced hump appears on their shoulders; the hump is a good way to distinguish a grizzly bear from a black bear, as black bears do not have this hump. Aside from the distinguishing hump a grizzly bear can be identified by a “dished in” profile of their face with short, rounded ears, whereas a black bear has a straight face profile and longer ears.  A grizzly bear can also be identified by its rump, which is lower than its shoulders, while a black bear’s rump is higher.  A grizzly bear’s front claws measure about 2–4 inches in length and a black bear’s measure about 1–2 inches in length.

Range and Population of Grizzly Bears

Brown bears are found in Asia, Europe, and North America, giving them the widest ranges of bear species.  They also inhabited North Africa and the Middle East.  In North America, grizzly bears previously ranged from Alaska down to Mexico and as far east as the western shores of Hudson Bay;[9] the species is now found in Alaska, south through much of western Canada, and into portions of the northwestern United States (including Idaho, Montana, Washington, and Wyoming), extending as far south as Yellowstone and Grand Teton National Parks. It is most commonly found in Canada. In Canada, there are approximately 25,000 grizzly bears occupying British Columbia, Alberta, the Yukon, the Northwest Territories, Nunavut, and the northern part of Manitoba.

Hibernating Grizzly Bears

After hibernationGrizzly bears hibernate for 5–7 months each year except where the climate is warm, as the California grizzly did not hibernate.  During this time, female grizzly bears give birth to their offspring, who then consume milk from their mother and gain strength for the remainder of the hibernation period.  To prepare for hibernation, grizzlies must prepare a den, and consume an immense amount of food as they do not eat during hibernation. Grizzly bears do not defecate or urinate throughout the entire hibernation period. The male grizzly bear’s hibernation ends in early to mid-March, while females emerge in April or early May.  In preparation for winter, bears can gain approximately (400 lb), during a period of hyperphagia (abnormally increased appetite for food), before going into hibernation.

Reproduction Habits of Grizzly Bears

Grizzly Sow with cubs in Glacier Park
Grizzly Sow with cubs in Glacier Park

Except for females with cubs, grizzlies are normally solitary, active animals, but in coastal areas, grizzlies gather around streams, lakes, rivers, and ponds during the salmon spawn. Every other year, females (sows) produce one to four young (usually two) that are small and weigh only about 1 lb at birth. A sow is protective of her offspring and will attack if she thinks she or her cubs are threatened.

Grizzly 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.

Life Span of Grizzly Bears

The grizzly bear is, by nature, a long-living animal. The average lifespan for a male is estimated at 22 years, with that of a female being slightly longer at 26.  Females live longer than males due to their less dangerous life; avoiding the seasonal breeding fights in which males engage. The oldest wild inland grizzly was 34 years old in Alaska; the oldest coastal bear was 39, but most grizzlies die in their first few years of life from predation or hunting.  Captive grizzlies have lived as long as 44 years.

Eating Habits and Diets of Grizzly Bears

Alaskan GrizzlyAlthough grizzlies are of the order Carnivore and have the digestive system of carnivores, they are normally omnivores: their diets consist of both plants and animals. They have been known to prey on large mammals, when available, such as moose, elk, caribou, white-tailed deer, mule deer, bighorn sheep, bison, and even black bears; though they are more likely to take calves and injured individuals rather than healthy adults. 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 inland individuals. Grizzly bears also readily scavenge food or carrion left behind by other animals.  Grizzly bears will also eat birds and their eggs, and gather in large numbers at fishing sites to feed on spawning salmon. They frequently prey on baby deer left in the grass, and occasionally they raid the nests of raptors such as bald eagles.

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 diets. In Yellowstone National Park in the United States, the grizzly bear’s diet consists mostly of white bark pine nuts, tubers, grasses, various rodents, army cutworm moths, and scavenged carcasses.[56] None of these, however, match the fat content of the salmon available in Alaska and British Columbia. With the high fat content of salmon, it is not uncommon to encounter grizzlies in Alaska weighing 1,200 lb.

Although the diets of grizzly bears vary extensively based on seasonal and regional changes, plants make up a large portion of them, 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, soapberries, 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, 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 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.

Ecological Role of the Grizzly Bear

North America Grizzly Bear
North America Grizzly Bear

The grizzly bear has several relationships with its ecosystem. One such relationship is a mutualistic relationship with fleshy-fruit bearing plants. After the grizzly consumes the fruit, the seeds are excreted and thereby dispersed in a germinable condition. Some studies have shown germination success is indeed increased as a result of seeds being deposited along with nutrients in feces.  This makes grizzly bears important seed distributors in their habitats.

While foraging for tree roots, plant bulbs, or ground squirrels, bears stir up the soil. This process not only helps grizzlies access their food, but also increases species richness in alpine ecosystems.  An area that contains both bear digs and undisturbed land has greater plant diversity than an area that contains just undisturbed land.[99] Along with increasing species richness, soil disturbance causes nitrogen to be dug up from lower soil layers, and makes nitrogen more readily available in the environment. An area that has been dug by the grizzly bear has significantly more nitrogen than an undisturbed area.

Nitrogen cycling is not only facilitated by grizzlies digging for food, it is also accomplished via their habit of carrying salmon carcasses into surrounding forests.  It has been found that spruce tree (Picea glauca) foliage within 1,600 ft of the stream where the salmon have been obtained contains nitrogen originating from salmon on which the bears preyed.  These nitrogen influxes to the forest are directly related to the presence of grizzly bears and salmon.

Grizzlies directly regulate prey populations and also help prevent overgrazing in forests by controlling the populations of other species in the food chain.  An experiment in Grand Teton National Park in Wyoming in the United States showed removal of wolves and grizzly bears caused populations of their herbivorous prey to increase.  This, in turn, changed the structure and density of plants in the area, which decreased the population sizes of migratory birds.  This provides evidence grizzly bears represent a keystone predator, having a major influence on the entire ecosystem they inhabit.

When grizzly bears fish for salmon along the coasts of Alaska and British Columbia, they often only eat the skin, brain and roe of the fish. In doing so, they provide a food source for gulls, ravens, and foxes, all of which eat salmon as well; this benefits both the bear and the smaller predators.

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