Interesting Creatures… Grizzly bear

Feb 07, 2021 Interesting Creatures in Guyana, News

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Kaieteur News – The grizzly bear (Ursus arctos horribilis), also known as the North American brown bear or simply grizzly, is a large population or subspecies of the brown bear inhabiting North America.
In addition to the mainland grizzly (Ursus arctos horribilis), other morphological forms of brown bear in North America are sometimes identified as grizzly bears. These include two living populations — the Kodiak bear (U. a. middendorffi) and the peninsular grizzly (U. a. gyas) — as well as the extinct California grizzly (U. a. californicus†), Mexican grizzly (U. a. nelsoni†), and Ungava-Labrador grizzly (U. a. ungavaesis†). On average, grizzly bears near the coast tend to be larger while inland grizzlies tend to be smaller.
The Ussuri brown bear (U. a. lasiotus), inhabiting Russia, Northern China, Japan, and Korea, is sometimes referred to as the “black grizzly”, although it is no more closely related to North American brown bears than other subspecies of brown bear around the world.

APPEARANCE
Most 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 hind foot length of 28 cm (11 in). 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). For a female, these average weights would be 136 kg (300 lb) inland and 227 kg (500 lb) coastal, respectively. One study found that the average weight for an inland male grizzly was around 272 kilograms (600 pounds), and the average weight for a coastal male was around 408 kg (899 lb).
Occasionally a huge male grizzly has been recorded, whose size greatly exceeds ordinary, 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.
Although variable in colour 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.

CHARACTERISTICS
A pronounced muscular hump appears on adult grizzlies’ shoulders; 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; a black bear’s rump is higher than its shoulders.
A grizzly bear’s front claws measure about 2–4 inches in length; a black bear’s claws measure about 1–2 inches in length.

HIBERNATION
Grizzly bears hibernate for 5–7 months each year except where the climate is warm, as the California grizzly does 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 180 kg (400 lb), during a period of hyperphagia, before going into hibernation. The bear often waits for a substantial snowstorm before it enters its den: such behaviour 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. 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. 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.

REPRODUCTION
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. Females (sows) produce one to four young (usually two) that are small and weigh only about 450 grams (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.
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. Population fragmentation of grizzlies may destabilize the population from inbreeding depression. The gestation period for grizzly bears is approximately 180–250 days.
Litter size is between one and four cubs, averaging twins or triplets. Cubs are always born in the mother’s winter den while she is in hibernation. Female grizzlies are fiercely protective of their cubs, being able to fend off predators as large as male bears bigger than they are in defence of the cubs. Cubs feed entirely on their mother’s milk until summer comes, after which they still drink milk but begin to eat solid foods. Cubs gain weight rapidly during their time with the mother—their weight will have increased from 4.5 to 45 kg (10 to 99 lb) in the two years spent with the mother. Mothers may see their cubs in later years but both avoid each other.

LONGEVITY
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; they do not engage in seasonal breeding fights as males do. The oldest wild inland grizzly was 34 years old in Alaska; the oldest coastal bear was 39, but most grizzlies die in their first year of life. Captive grizzlies have lived as long as 44 years. (Source: Wikipedia)

 

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