The grizzly bear (Ursus arctos horribilis) is known by other names such as the grizzly or North American brown bear. It is a large subspecies or population of the brown bear native to North America.
Aside from the mainland grizzly (Ursus arctos horribilis), other morphological forms of brown bear are sometimes identified as grizzly bears in North America.
These include two extant populations; the peninsular grizzly (U. a. gyas) and the Kodiak bear (U. a. middendorffi).
Others include the extinct Mexican grizzly (U. a. nelsoni†), California grizzly (U. a. californicus†), and Ungava-Labrador grizzly (U. a. ungavaesis†). Grizzly near the coast tend to be larger than the inland grizzlies.
The Ussuri brown bear (U. a. lasiotus), native to Northern China, Russia, Korea, and Japan, is often referred to as the black grizzly.
It is more closely related to the North American brown bear than other subspecies of brown bears.
Scientific classification
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Mammalia |
| Order | Carnivora |
| Family | Ursidae |
| Genus | Ursus |
| Species | U. arctos |
| Subspecies | U. a. horribilis |
Characteristics
Most adult female grizzlies weigh 290 to 400 lb (130 to 180 kg), while the adult male weighs on average 400 to 790 lb (180 to 360 kg). The average length in this subspecies is 6.50 ft (198 cm), with an average shoulder height of (3.35 ft) 102 cm and hindfoot length 11 in (28 cm).
Newborns may weigh less than 1.1 lb (500 lb). Mature female grizzlies can weigh 220 lb (100 kg) in the Yukon River area. For a female, the average weight would be 300 lb (136 kg) inland and 500 lb (227 kg) coastal, respectively.
A report indicated that the average weight for an inland male grizzly was around 600 pounds (272 kilograms and the average weight for a coastal male was 899 lb (408 kg).
Sometimes a huge male grizzly bear has been recorded, whose size greatly exceeds the normal, with weight reported up to 1,500 lb (680 kg). A large coastal male may stand up to 9.8 ft (3 metres) tall on its hind legs and be up to 4.9 ft (1.5 metres) at the shoulder.
Although variable in colour from blonde to nearly black, the fur of the grizzly bear is brown with darker legs and commonly blonde or white-tipped fur on the back and flank.
A grizzly bear’s front claws measure about 2 to 4 inches in length; a black bear’s claws measure about 1 to 2 inches in length.
Reproduction
Except for females with cubs, grizzlies are normally active, solitary animals, but in coastal areas, grizzlies gather around rivers, streams, ponds, and lakes during the salmon spawn.
Females (sows) produce 1 – 4 young (usually 2) that are small and weigh only about 1 lb (450 grams) at birth. Grizzly bears are known to have the lowest reproductive rates among all terrestrial mammals in North America.
Grizzly bears reach sexual maturity at 5 years old. After mating, the female delays embryo implantation until hibernation period, during which miscarriage may occur if the female does not receive the proper caloric intake and nutrients.
Females produce 2 cubs in a litter, and the mother cares for her cubs for up to 2 years, after which the mother will mate again.
A male grizzly bear can have a large territory, up to 1,500sq mi (4,000 km2), making it difficult to find females in low populations. The gestation period may last up to 180 to 250 days. Litter size is between 1 – 4 cubs, averaging 2 to 3 cubs.
Cubs experience rapid growth when they are with their mother; their weight will have increased from 10 – 99 lb (4.5 – 45 kg) in two years. The cubs and the mother might meet later years on, but they will avoid each other.
The average lifespan for a female is estimated at 26 years, with that of a male being slightly shorter at 22. In captivity, grizzlies are known to live as long as 44 years. The oldest wild grizzly bear was 34 years old in Alaska, while the oldest coastal bear was 39 years old.
Hibernation
Grizzly bears hibernate for 5 to 7 months each year, except where the climate temperature is warm. California grizzlies do not hibernate due to the warm climate in California.
Before hibernation, grizzlies prepare a den and also consume an immense amount of food as they do not feed during hibernation. Grizzlies do not urinate or defecate throughout the entire hibernation period.
The female grizzly bear’s hibernation ends April or May, while males emerge in mid-March.
Diet
Grizzly bears are categorized under the order Carnivora and are known to have the digestive system of carnivores. They are primarily omnivores; their diet consists of both animals and plants.
Grizzlies are known to prey on large mammals, when available, such as elk, moose, white-tailed deer, caribou, bighorn sheep, mule deer, black bears, and bison.
They are more likely to prey on injured individuals or calves rather than healthy adults. Grizzly bears feed on fish such as trout, salmon, and bass.
The grizzlies diet also consists of blackberries (Rubus fruticosus), blueberries, cranberries (Vaccinium oxycoccos), salmon berries (Rubus spectabilis), soapberries (Shepherdia canadensis), buffalo berries (Shepherdia argentea), and huckleberries (Vaccinium parvifolium).
