North American bears: get to know a little bit about the three most common species.
Bears inhabit all of the northern hemisphere --North America, Europe and Asia and South America. They are absent from Africa and Australia--the koala bear is not really a bear, but a marsupial, related to kangaroos. North America is home to three species of bears: the American black bear, the brown bear and the polar bear. Each species has its own interesting biology and ecology as well as folklore.
American black bear
The smallest and most widespread species of bear in North America is the American black bear (Ursus americanus). Black bears are found mostly in forested areas from Alaska to central Mexico. In several areas of their range, black bears live in close proximity to humans, which often leads to conflicts. Although attacks on humans may result from these encounters, black bears are more likely to flee from humans than they are to attack.
Black bears vary in size depending on geography and the sex of the bear. Bears in the northern part of their range tend to be larger than their southern cousins. Male bears, which weigh anywhere from 120 to more than 600 pounds, are also larger than females, which typically range from 90 to 300-plus pounds. Both males and females vary in length from about 4 to 6 feet.
While most black bears actually are black, there is some variation in their fur color throughout their range. In the western United States and Canada, they are often brown, cinnamon or buff colored. On the coast of Alaska and British Columbia, black bears often have distinctive blue-gray fur and are called glacier bears, while others have white fur.
Bears of all kinds have a reputation of being ferocious predators, but the American black bear is actually an omnivore, meaning it eats both plants and animals. Actually, black bears feed mostly on plant material, such as berries, nuts and seeds. They also feed heavily on insects and other small animals like crayfish and snails. Their curved claws are ideal for pulling the bark off of logs and digging under leaves for insect larvae and worms. One of the black bear's main sources of protein is ant eggs.
Black bears are ready to reproduce at around 2 years of age, and female bears give birth to cubs every two years. They mate in the spring, the embryo implants in late fall, and the cubs are born in January or February, at which time their mother is in a torpid state. Depending on food availability and the health of the mother, the number of cubs varies, ranging from one to six, with two to three being the most common. The cubs are born bald and blind, and remain with their mother in the den nursing until the mother and cubs emerge in the spring.
Contrary to popular belief, black bears do not truly hibernate. In the more northerly parts of their range, however, they do enter a state of dormancy (torpor) in the winter, in which their metabolism slows down considerably.
During this time, they locate a den--a hollow tree, log or cave--where they do not eat, drink or excrete waste.
They may occasionally wake during this time, but only for short periods. When their winter sleep is over, black bears emerge from their dens many pounds lighter than when they entered.
The brown bear (Ursus arctos) is the most widely distributed bear in the world. Brown bears are found throughout North America, northern Asia, and at one time, most of Europe. In North America, brown bears are now found mostly in wilderness areas of Alaska, western Canada, and the U.S. Rocky Mountains. North American brown bears are generally divided into two subspecies: the grizzly bear (Ursus arctos horribilis), so named because of its silver-tipped hairs that give it a grizzled appearance, and the Kodiak bear (Ursus arctos middendorffi), found on Kodiak Island and a few nearby islands off the coast of Alaska.
The grizzly bear is mostly an inland species, being found in the forests and tundra areas of the United States and Canada. In the lower 48 states, grizzlies are found mostly in the Yellowstone ecosystem of Wyoming, Montana and Idaho. They are also relatively abundant in the region around Glacier National Park in northern Montana. At one time, grizzlies numbered in the thousands in the lower 48 states. There are now only about 1,200 left, being confined to only the wildest remaining areas.
Grizzlies have among the largest home ranges of any mammal, sometimes requiring 1,000 square miles. Such larger home ranges are typically in areas where potential food is sparse, causing these animals to become more aggressive in their search for food. When humans come into the same areas, there are usually conflicts, with the bears losing out more often than not. Grizzlies, like black bears, are omnivores, feeding heavily on berries, nuts, grasses and roots, but relying much more on animals. Grizzly bears will readily attack and eat moose, deer, elk and black bears. Adult males will also kill and eat young grizzlies if the opportunity presents itself.
Kodiak bears and their coastal cousins are usually less aggressive because they have an abundant source of high-protein food--fish. Such easy access to food and the more moderate climate of the coastal environment, which equals year-round access to food, means Kodiaks are generally larger than their inland relatives. Where a male grizzly typically weighs 500 to 800 pounds and stands 4 feet tall on all fours and around 8 feet tall upright, Kodiaks tend to weigh between 1,000 and 1,500 pounds and stand 5 feet tall at the shoulder and 10 feet tall or more when upright.
The polar bear (Ursus maritimus) is not only generally considered the largest bear species in the world--the Kodiak is argued by some, and "largest" isn't always defined in the same way--it is also the largest land-dwelling predator in the world. A full-grown male polar bear can stand up to 11 feet tall on its hind legs and weigh 1,500 pounds or more. Females are somewhat smaller, but may still tip the scales at more than 700 pounds and stand up to 8 feet tall when upright.
The most notable trait of polar bears is their white fur, which really isn't white at all. The outer guard hairs of a polar bear's fur are actually clear and hollow, like glass fibers. These guard hairs--which help trap heat and light, and also help shed water can give the fur a white, yellow or even greenish appearance, depending on lighting conditions. Under their fur is a thick layer of blubber that keeps them warm in the frigid Arctic waters.
Polar bears live throughout the Arctic regions of Alaska and Canada, primarily near the ocean, although some have been seen up to 100 miles inland. Because of their webbed forepaws, polar bears are extremely strong swimmers--they can swim up to 60 miles without rest and dive
up to 20 feet. In the United States, polar bears are classified as marine mammals, like whales and seals, and are protected as such.
The most carnivorous of the three North American bear species, the polar bear feeds almost exclusively on seals and occasionally on sea birds. Polar bears that wander inland are more likely to feed on plant material, but this is rare. As for seals, polar bears prefer the blubber, because it helps them maintain a high body fat content, which in turn keeps them warm in winter.
Only female polar bears hibernate in the winter, digging igloolike dens in the snow and ice. The den is where they spend the harshest part of the winter and give birth to their young. At 4 or 5 years of age, female polar bears are ready to reproduce. Mating occurs in the spring, and like their black and brown cousins, the polar bear embryo does not implant right away, only after the adult female has entered her den. Around December or January, a litter of one to four cubs--two being the most common--are born, weighing a mere pound or so.
In the warmth of the den, the cubs are nursed and protected until spring, when they are ready to emerge. The cubs will stay with their mother until they are 2 or 3 years old, at which time they are capable of surviving on their own.
The future of bears As with many species of wildlife, bears face numerous obstacles in this human-dominated world. Habitat loss is especially serious for bears, since they are large animals requiring large wilderness areas in which to live. All three species of North American bears have declined in numbers in the last few decades. To ensure that we always have these bears with us, we have to make room for these magnificent creatures in our world.
ON THE WEB
Meet the Great Blue Heron (http://bit.ly/1gF50W7).
John Marshall is a retired college instructor from central Arkansas, who has long contributed to the pages of Grit and CAPPERs.
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|Title Annotation:||In the Wild|
|Date:||Sep 1, 2014|
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