Grizzly bear

The grizzly bear (Ursus arctos ssp.) is any North American subspecies of brown bear, including the mainland grizzly (Ursus arctos horribilis), Kodiak bear (U. a. middendorffi), peninsular grizzly (U. a. gyas), and the recently extinct California grizzly (U. a. californicus†) and Mexican grizzly bear (U. a. nelsoni†). Specialists sometimes call the grizzly the North American brown bear because the grizzly and the brown bear are one species on two continents.^[It should not be confused with the black grizzly or Ussuri brown bear (U. a. lasiotus) which is another giant brown bear subspecies inhabiting Russia, Northern China, and Korea.^[
Since the mainland grizzly is so widespread, it is representative and archetypal for the whole subspecific group. Even so, classification is being revised along genetic lines.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)^[which are small and weigh only about 500 grams (1 lb) at birth. A sow is protective of her offspring and will attack if she thinks she or her cubs are threatened.

 

Classification

Meaning of "grizzly"

The word "grizzly" means "grizzled"; that is, golden and grey tips of the hair. This is not to be confused with the word "grisly". Nonetheless, after careful study, naturalist George Ord formally classified the California grizzly in 1815—not for its hair, but for its character—as Ursus horribilis.

Evolution and genetics

The ancestors of the grizzly bear subspecies were brown bears originating in Eurasia that traveled to North America approximately 50,000 years ago.^] This is a very recent event, on an evolutionary timescale, causing the North American grizzly bear to be very similar to brown bears inhabiting Siberia and northeast Asia. The closest Eurasian subspecies to the grizzly bears are believed to be the Ussuri brown bear (U. a. lasiotus) for mainland grizzlies and the Kamchatka brown bear (U. a. beringianus) for the coastal Alaskan and Kodiak bears which arrived in North America shortly before the Bering land bridge flooded.
When it received its scientific name in 1815, the grizzly was classified as a separate species from all other bears. However, modern genetic testing reveals the grizzly to be a subspecies of the brown bear (Ursus arctos). So in Eurasia, it is the "brown bear"; in North America, it is the "grizzly".
In other words, the grizzly and the brown bear are one species on two continents. Currently, Rausch and others classify three subspecies of the new "North American brown bear": U. a. horribilis, middendorffi, and gyas. But more recent studies of mtDNA suggest that this three-fold division of living grizzlies needs revision. Further testing of Y-chromosomes is required to yield an accurate new taxonomy with different subspecies.
Coastal grizzlies, often referred to by the popular but geographically redundant synonym of "brown bear" or "Alaskan brown bear" are larger and darker than inland grizzlies, which is why they, too, were considered a different species from grizzlies. Kodiak grizzly bears were also at one time considered distinct. Thus, at one time there were five different "species" of brown bear, including three in North America.

Appearance

Most adult female grizzlies weigh 130–200 kg (290–440 lb), while adult males weigh on average 180–360 kg (400–790 lb). Average total length in this subspecies is 198 cm (6.50 ft), with an average shoulder height of 102 cm (3.35 ft) and hindfoot length of 28 cm (11 in).^[ Newborn bears may weigh less than 500 grams (1.1 lb). In the YukonRiver area, mature female grizzlies can weigh as little as 100 kg (220 lb). One study found that the average weight for an inland male grizzly was around 270 kilograms (600 lb) and the average weight for a coastal male was around 408 kilograms (900 lb). For a female, these average weights would be 136 kilograms (300 lb) inland and 227 kilograms (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 680 kg (1,500 lb).^[A large coastal male of this size may stand up to 3 metres (9.8 ft) tall on its hind legs and be up to 1.5 metres (4.9 ft) at the shoulder.Althouh 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. 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 their rump which is lower than their shoulders where a black bears rump is higher. A grizzly bears front claws measure about 2-4 inches in length and a black bears measure about 1-2 inches in length.

Range and population

Brown bear in Katmai National Park with partially eaten salmon - the heads, skin and subcutaneous tissue are eaten to obtain the most fat

Brown bears are found in Asia, Europe, and North America, giving them one of 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;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, but 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. In British Columbia, grizzly bears inhabit approximately 90% of their original territory. There were approximately 25,000 grizzly bears in British Columbia when the European settlers arrived.However, population size has since significantly decreased due to hunting and habitat loss. In 2008, it was estimated there were 16,014 grizzly bears. Population estimates for British Columbia are based on hair-snagging, DNA-based inventories, mark-recapture, and a refined multiple regression model. In 2003, researchers from the University of Alberta spotted a grizzly on Melville Island in the high Arctic, which is the most northerly sighting ever documented.
The Alaskan population of 30,000 individuals is the highest population of any province/state in North America. Populations in Alaska are densest along the coast, where food supplies such as salmon are more abundant. The Admiralty Island National Monument protects the densest population — 1,600 bears on a 1,600-square mile island.

Continental United States

Only about 1,500 grizzlies are left in the lower 48 states of the US. Of these, about 800 live in Montana. About 600 more live in Wyoming, in the Yellowstone-Teton area. There are an estimated 70–100 grizzly bears living in northern and eastern Idaho. Its original range included much of the Great Plains and the southwestern states, but it has been extirpated in most of those areas. Combining Canada and the United States, grizzly bears inhabit approximately half the area of their historical range.
In September 2007, a hunter produced evidence of grizzly bears returning to the Selway-Bitterroot Wilderness ecosystem, on the central Idaho and western Montana border, by killing a male grizzly bear there. In the North Cascades ecosystem of northern Washington grizzly bear populations are estimated to be less than 20 bears and only one sighting of a grizzly bear in the last 10 years has been recorded.  There is the possibility that Grizzlies may begin repopulating in Colorado, although there has been no confirmed sighting of a grizzly in that state since 1979.

Hibernation

Grizzly 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.

Reproduction

Sow with two cubs

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 litte 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 km² (1,500 sq mi), 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. The gestation period for grizzly bears is approximately 180–250 days.

Diet

Grizzly bear fishing for salmon at Brooks Falls, Alaska

Mother grizzly with a cub

Although grizzlies are of the order Carnivora 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 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.