Bears (Ursus species) are large, four-legged mammals that have a unique status in pop culture. They are not quite as cuddly as dogs or cats; not quite as dangerous as wolves or mountain lions; but they are decidedly ever-compelling objects of fear, admiration, and even envy.Found in a variety of environments from Arctic ice pack to tropical forests, bears live on every continent except Antarctica.
Fast Facts: Bears
- Scientific Name: Ursus spp
- Common Names: Bear, panda
- Basic Animal Group: Mammal
- Size (length): Sun bear: 4–5 feet; brown bear: 5–10 feet
- Weight: Sun bear: 60–150 pounds; brown bear 180–1300 pounds
- Lifespan: 20–35 years
- Habitat: Woodlands, grasslands, deserts, temperate and tropical forests, on all continents except Antarctica
- Conservation Status: Least Concern: Brown bears, American black bear; Vulnerable: sloth bear, polar bear, giant panda, sun bear, spectacled bear, Asian black bear
With some minor exceptions, all eight bear species haveroughly the same appearance: large torsos, stocky legs, narrow snouts, long hair, and short tails. With their plantigrade postures—walking upright on two feet—bearswalk flat-footed on the ground like humans but unlike most other mammals.
Bears range in color with species: Black, brown and Andean bears are typically red-brown to black; polar bears are generally white to yellow; Asiatic bears are black to brown with a white patch and sun bears are brown with a yellow crescent on their chest.They range in size from the sun bear (47 inches tall and weighing 37 pounds) to the polar bear, (nearly 10 feet tall and weighing 1,500 pounds).
Scientists recognize eight species as well as numerous subspecies of bears, which live in different regions, that have differences in body shape and coloration.
American black bears(Ursus americanus)live inNorth America and Mexico; their diet consists primarily of leaves, buds, shoots, berries, and nuts. Subspecies of this bear include the cinnamon bear, the glacier bear, the Mexican black bear, the Kermode bear, the Louisiana black bear,and several others.
Asian black bears (Ursus thibetanus)live in Southeast Asia and the Russian Far East. They have blocky bodies and patches of yellowish-white fur on their chests, but otherwise resemble American black bears in body shape, behavior, and diet.
Brown bears (Ursus arctos)are some of the world's largest terrestrial meat-eating mammals. They range across North America, Europe, and Asia and include numerous subspecies, such as the Carpathian bear, the European brown bear, the Gobi bear, the grizzly bear, the Kodiak bear,and several others.
Polar bears(Ursus maritimus)rival brown bears in size. These bears are restricted to a circumpolar region in the Arctic, reaching south into northern Canada and Alaska. When they're not living on pack ice and shorelines, polar bears swim in open water, feedingon seals and walruses.
Giant pandas(Aeluropoda melanoleuca)feed almost exclusively on bamboo shoots and leaves in the central and southern regions of western China. These distinctly patterned bears have black bodies, white faces, black ears,and black eyespots.
Sloth bears (Melursus ursinus)stalk the grasslands, forests, and scrublands of Southeast Asia. These bears have long, shaggy coats of fur and white chest marks; they feed on termites, which they find using their acute sense of smell.
Spectacled bears(Tremarctos ornatos) are the only bears native to South America, inhabiting cloud forests at elevations over 3,000 feet. These bears once lived in coastal deserts and high-elevation grasslands, but human encroachmenthas restricted their range.
Sun bears(Helarctos malayanos) live in the lowland tropical forests of Southeast Asia. These small ursineshave the shortest fur of any bear species, their chests marked with light, reddish-brown, U-shaped patches of fur.
Diet and Behavior
Most bears are omnivorous, feasting opportunistically on animals, fruits, and vegetables, with two important outliers: The polar bear is almost exclusively carnivorous, preying on seals and walruses, and the panda bear subsists entirely on bamboo shoots. Oddly enough, though, pandas' digestive systems are relatively well adapted to eating meat.
Because the vast majority of bears live in high northern latitudes, they need a way to survive the winter months when food is dangerously scarce. Evolution's solution is hibernation: Bears go into a deep sleep, lasting for months, during which their heart rates and metabolic processes slow drastically. Being in hibernation isn't like being in a coma. If sufficiently roused, a bear can wake up in the middle of its hibernation, and females have even been known to give birth in the deep of winter. Fossil evidence also supportscave lions preying on hibernating cave bears during the last Ice Age, though some of these bears woke up and killed the unwelcome intruders.
Bears may be the most antisocial mammals on the face of the earth. Full-grown bears are almost entirely solitary. This is good news for campers who accidentally encounter lone grizzlies in the wild, but quite unusual when compared with other carnivorous and omnivorous mammals, ranging from wolves to pigs, that tend to congregate in at least small groups.
Depending on species, a bear's basic communication needs can be expressed withabout seven or eight different "words"—huffs, chomps, groans, roars, woofs, growls, hums, or barks. The most dangerous sounds for humans are roars and growls, which denote a frightened or agitated bear defending its territory.
Huffs are generally produced during mating and courtship rituals; hums—a bit like the purrs of cats, but much louder—are deployed by cubs to demand attention from their mothers, and moans express anxiety or a sense of danger. Giant pandas have a slightly different vocabulary than their ursine brethren: In addition to the sounds described above, they can also chirp, honk, and bleat.
Given the proliferation of so-called bear dogs millions of years ago—including the standard-bearer of the family, Amphicyon—you might assume that modern bears are most closely related to dogs. In fact, molecular analysis shows that the closest living relatives of bears are pinnipeds, the family of marine mammals that includes seals and walruses. Both of these mammalian families descend from a last common ancestor, or "concestor," that lived sometime during the Eocene epoch, about 40 million or 50 million years ago. The exact identity of the progenitor species, however, remains a matter of speculation.
Given that the populations of medieval Europe didn't have much contact with polar bears or panda bears, it makes sense that European peasantsassociated bears with the color brown—which is where the English name of this animal derives, from the old Germanic root bera. Bears are also known asursines, a word that has ancient roots in Proto-Indo-European languages that were spoken as far back as 3500 BCE. The long history of this word makes sense, given that the first human settlers of Eurasia lived in close proximity to cave bearsand sometimes worshiped these beasts as gods.
Reproduction and Offspring
Like their close cousins seals and walruses, bears are some of the most sexually dimorphic animals on earth—that is to say, male bearsare significantly bigger than females, and, what is more, the bigger the species, the largerthe disparity in size. In the largest brown bear subspecies, for instance, males weigh about 1,000 pounds and females only slightly more than half that.
However, even though female bears are smaller than males, they're not exactly helpless. They vigorously defend their cubs from male bears, not to mention any humans foolish enough to interfere with the child-rearing process. Male bears, however, will sometimes attack and kill cubs of their own kind, in order to induce females to breed again.
Although there are some differences among the species, in general, female bears generally become sexually mature at between 4 and 8 years of age and have litters every three or four years. Bear breeding occurs during the summers—it is the only time when adult bears get together at all—but implantation doesn't typically occur until late autumn. Total gestation time is 6.5–9 months. Cubs are born singly or up to three at a time, generally in January or February, while the mother is still in hibernation. The young usually stay with their mother for two years. After mating, females are left to raise the young by themselves for a period of about three years, at which point—eager to breed with other males—the mothers chase the cubs away to fend for themselves.
Considering that early humans used to worship bears as gods, our relationship with ursines hasn't exactly been stellar over the last few hundred years. Bears are especially susceptible to habitat destruction, are often hunted for sport, and tend to become the scapegoats whenever campers are attacked in the wild or garbage cans are overturned in suburbs.
Today, the largest threats to bears are deforestation and human encroachment, and, for polar bears, climate change which is reducing the environment in which they live. On the whole, black and brown bears are holding their own, even though adverse interactions with humans have increased as their habitats become more constricted.
According to the International Union for Conservation of Nature, the sun bear, sloth bear, Asiatic, and spectacled bears are all listed as Vulnerable and decreasing in population; the polar bear is also listed as Vulnerable but its population status is unknown. The American black bear and brown bear is considered Least Concern and increasing in numbers. The giant panda is Vulnerable but increasing in population.
Bears and Humans
Within the past 10,000 years, human beings have domesticated cats, dogs, pigs, and cattle—so why not bears, an animal with which Homo sapiens has coexisted since the end of the Pleistocene epoch?
One explanation is that since bears are intensely solitary animals, there's no room for a human trainer to insert himself into the "dominance hierarchy" as the alpha male. Bears also pursue such varied diets that it would be difficult to keep even a tame population well-supplied. Perhaps most importantly, bears are anxious and aggressive when stressed, and simply don't have suitable personalities to behouseor yard pets.
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