Bears

All bears belong to the taxonomic family ursidae, which is comprised of all eight extant species of bear. Ursidae is divided into three subfamilies, which are ursinae, tremarctinae, and ailuropodinae. Ursinae is the largest of these subfamilies, containing American black bears, brown bears (of which grizzly bears are a subspecies), polar bears, sloth bears, sun bears, and Asian black bears.The subfamily tremarctinae, on the other hand, contains only the spectacled bear. Ailuropodinae also contains only one extant species, the giant panda.

Even though few species of them exist, and most are endangered, bears are very widespread, being found in Europe, Asia, North America, and South America. The most widespread species of bear is the brown bear, which can be found throughout the former three continents. The bear species residing in the narrowest range is the spectacled bear, which populates only the Andean region of South America, and is the only species of bear found on that continent. Polar bears are found only on the Arctic Sea, and American black bears are confined to North America; the remaining four species reside in Asia.

Bears tend to inhabit forests, with the exception of polar bears, which live at sea and on sea ice and Arctic archipelagos. Some bears, especially the brown bear, may be found in alpine shrubland or tundra, in which they may reside either seasonally or permanently.

When the climate of many bears' habitats becomes cold and food becomes scarce, these species of bear retreat to their dens and enter a deep state of rest. This habit is colloquially known as hibernation, though it is not a true hibernation; bears' breathing, heart rate, and metabolic rates slow only a little bit, their body temperatures do not drop considerably, and they may occasionally rouse from this state, while true hibernators experience more significant changes to their bodily processes and do not rouse from hibernation.

Bears are large creatures with heavy bodies, long sharp claws, relatively short legs, and large heads with long, canine teeth. They range in weight across species, with the smallest species, the sun bear, weighing between 100 and 140 lb on average, and the largest species, the polar bear, weighing an average of 850-900 lb. The largest individuals, however, are often brown bears, with some subspecies weighing up to 1,180 lb on average. Bears are quadrupedal, meaning they walk on four legs, but can stand on two legs and sit as humans do.

Despite their reputation for being voracious carnivores, bears, with the exception of polar bears and giant pandas, are usually omnivorous. (Polar bears are carnivores relying a diet of mostly on marine mammals, while giant pandas eat mostly bamboo.) Bears' diets are determined largely by their environment, as they will feed on any food source that is available to them. They use their exceptional sense of smell to locate food and prey. Bears are predominantly predators and tend not to be prey; the only routine natural predator of adult bears is the tiger, which inhabits only Asia.

About the Author
Jacob Maddox manages content for Wildlife Animals http://www.wildlife-animals.com an educational wildlife and animal website.