Grizzly Bear
Ursus arctos horribilis
Summary 2
ost adult female grizzlies weigh 130–180 kg (290–400 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).[16] Newborn bears may weigh less than 500 grams (1.1 lb). In the Yukon River 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 272 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.[17] 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).[18] 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.[19]
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.[20] 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.[21] A grizzly bear can also be identified by its rump, which is lower than its shoulders, while a black bear's rump is higher.[21] 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.[21]
Brown bears are found in Asia, Europe, and North America, giving them the widest ranges of bear species.[2] They also inhabited North Africa and the Middle East.[22] 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.[9] An article published in 1954 suggested they may be present in the tundra areas of the Ungava Peninsula and the northern tip of Labrador-Quebec.[23] 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.[9] However, population size has since significantly decreased due to hunting and habitat loss. 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.[24][25] 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-and-recapture, and a refined multiple regression model.[26] A revised Grizzly bear count in 2012 for British Columbia was 15,075.[27]
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.[28] The Admiralty Island National Monument protects the densest population—1,600 bears on a 1,600-square mile island.[29]
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.[54] 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.[55]
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.[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 540 kg (1,200 lb).[57] Grizzlies in Alaska supplement their diet of salmon and clams with sedge grass and berries. In areas where salmon are forced to leap waterfalls, grizzlies gather at the base of the falls to feed on and catch the fish. Salmon are at a disadvantage when they leap waterfalls because they cluster together at their bases and are therefore easier targets for the grizzlies.[58] Grizzly bears are well-documented catching leaping salmon in their mouths at Brooks Falls in Katmai National Park and Preserve in Alaska. They are also very experienced in chasing the fish around and pinning them with their claws.[59][60] At such sites such as Brooks Falls and McNeil Falls in Alaska, big male grizzlies fight regularly for the best fishing spots.[61] Grizzly bears along the coast also forage for razor clams, and frequently dig into the sand to seek them.[62] During the spring and fall, directly before and after the salmon runs, berries and grass make up the mainstay of the diets of coastal grizzlies.[63]
Grizzly bears hibernate for 5–7 months each year[37] except where the climate is warm, as the California grizzly did not hibernate.[2] 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.[38] 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.[39]
In preparation for winter, bears can gain approximately 180 kg (400 lb), during a period of hyperphagia, before going into hibernation.[40] The bear often waits for a substantial snowstorm before it enters its den: such behavior lessens the chances predators will find the den. The dens are typically at elevations above 1,800 m (5,900 ft) on north-facing slopes.[41] 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.[42] Although inland or Rocky Mountain grizzlies spend nearly half of their life in dens, coastal grizzlies with better access to food sources spend less time in dens. In some areas where food is very plentiful year round, grizzly bears skip hibernation altogether.[43]
Sources and Credits
- (c) joecf, some rights reserved (CC BY-NC-ND), uploaded by joecf
- Adapted by calgaryzoo from a work by (c) Wikipedia, some rights reserved (CC BY-SA), https://en.wikipedia.org/wiki/Ursus_arctos_horribilis
