Talk:Bear

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Bears of the World
Though similar in many ways, bears can live in a wide range of environmental conditions and exhibit diverse behaviors. The bear family (Ursidae) is classified into three subfamilies, three genera, eight species, and numerous subspecies, depending on the source. They currently inhabit the continents of Eurasia, North America, and South America. Fossil evidence suggests that there were African species, but they have since gone extinct.

Many researchers agree that genus Ursus, whose species have 74 chromosomes, consists of the sun, sloth, brown, polar, American black, and Asiatic black bears. The spectacled bear is the only survivor of the short-faced bears, genus Tremarctos, and has 52 chromosomes. The giant panda makes up the other Genus, Ailuropoda, and has 42 chromosomes.

The Polar Bear
The polar bear (Ursus maritimus) has an Arctic range that covers more than one continent. On average, they are the biggest of today's bears and males reach weights of 1200 pounds (450 kg) or more. Polar bear hair is not white. Instead, the hair is transparent and made of hollow tubes that reflect light. Interestingly, some zoo bears have been known to turn green because of algae growing in the hollow spaces. Years ago, it was assumed that their black skin absorbed the light and produced increased warmth, enabling them to survive the coldest of conditions. However, polar bears are most active during the northern winters when there is little or no light. Physicists now realize that the keratin makeup of hair, not the skin, probably absorbs the light. In fact, polar bears are designed to resist the harsh Arctic weather because they are extremely well insulated with guard hairs, thick fur, and about 12 inches of blubber. Only the pregnant females hibernate and captive polar bears have produced fertile hybrid offspring with brown bears. The first wild grizzly/polar hybrid was shot, in northern Canada, in 2006. Genetic tests determined that the father was a grizzly and the mother was a polar bear.

The Brown Bear
The brown bear (Ursus arctos) is known for its shoulder hump, boxed nose, and dish-shaped face. Along with the polar bear, they also range over more than one continent. Brown bears are believed to have originated in Eurasia and later dispersed to North America where its territories collided with the American black bear (Ursus americanus). Russia has the highest population of brown bears. Like most bears, they display wide ranging food behaviors and, depending on the habitat, may eat anything from fruits and insects to fish and large deer. In recent years grizzlies (Ursus arctos horriblis), a sub species of brown bear, have been observed on sea ice hunting seals 60 miles from land. Depending on the source, brown bear subspecies may range from five to ninety. Others include Eurasia’s brown bear (Ursus arctos arctos) and the Kodiak brown bear (Ursus arctos middendorffi). Bible authors referred to bears 14 times in Scripture. The species they were familiar with was the smallest brown bear subspecies, the Syrian brown bear (Ursus arctos syriacus). Wild populations no longer live in Israel because they were extirpated in the early 20th century. Some wild populations may still be found in western Asia but are very low in number. Brown bears have been known to hybridize with American black, Asiatic black, and polar bears.

The Sun (Malayan) Bear
In the genus Helarctos is the sun bear (Helarctos malayanus). It spends a lot of time in trees and lives in the low lying rainforests of Southeast Asia. A light crescent shape is often a distinguishing mark on its chest. They give birth at various times of the year and tend to produce more females than males. In proportion to its size, the sun bear has one of the largest canine teeth of all bears, yet eats mostly fruit. It is presently classified a vulnerable species and continues to decline in numbers. It has hybridized with sloth and Asiatic black bears.

The Sloth Bear
The shaggy sloth bear (Ursus ursinus) is a unique bear that lives in lower elevation forests and grasslands of Southern Asia. Its distinguishing patterns usually consist of a “U” or “Y” emblazoned on the chest. They are one of the three bear species, including the giant panda and spectacled bears, that do not hibernate. While the other bears have 42 teeth, the sloth bear is missing its two upper incisors leaving it with only 40. Its lips are naked and it has the ability to close its nostrils, making it a successful insect eater. These adaptations allow them to use an unusual “vacuum cleaning” feeding behavior and can be heard 90 meters away “vacuuming” termites and ants. Mother bears often let the cubs ride on their backs. They have hybridized with sun bears.

The Asiatic Black Bear
Ursus thibetanus, or the Asiatic black bear, lives in eastern and southern Asia. They usually have a white or cream-colored "V" patterning on the chest. It is also called the “moon” bear and has a critically endangered subspecies called the Baluchistan bear (Ursus thibetanus gedrosianus). The Asiatic black bear is mostly herbivorous, sometimes eating bamboo, but also may eat deer and other animals. Living in mountain forests, they spend half their time in trees and make tree platforms for feeding and resting. It has produced hybrid offspring with spectacled, brown, sun and possibly American black bears. In some places, they may overlap with the giant panda and brown bear, while in India, they may share the habitat with sun and sloth bears.

The American Black Bear
The American black bear (Ursus americanus), actually comes in many colors often depending on where they live. Colors include black, blue-gray, cinnamon, and white. The white bear, also deemed the “Spirit” or “Kermode” bear, is a rare color form. It is typically found along the British Columbia coast and the Southeast panhandle of Alaska. The black bear is the only bear considered original to North America. Estimates of black bear populations are 500,000 individuals or more and greater than all other bears combined. They are regularly hunted as a game species in many parts of North America. Excellent tree climbers they often find a fixed position in the tree and pull fruit and mast laden branches toward them. When they eat their fill, the bent branches look like giant nests and are locally called "bear nests". They have hybridized with brown bears and may have hybridized with Asiatic black bears.

The Spectacled Bear
Subfamily Tremarctinae consists of the only living member of the short-faced bears, the spectacled or Andean bear (Tremarctos ornatus). Their faces have cream-colored or “spectacled” markings and they are the only bears of South America. Found in the tropical mountain forests of northern South America, they favor plant foods from the pineapple family (Bromeliaceae) and other fruits. Spectacled bears are the most arboreal of bears and spend much of their time in trees making platforms for eating and sleeping. This bear has not been observed to hibernate and, in captivity, they have hybridized with the Asiatic black bear and produced fertile offspring.

The Giant Panda
Subfamily Ailurinae contains the giant panda, Ailuropoda melanoleuca. With its white face and black eye patches, it represents an animal that people can connect with and care about. Because of this, the giant panda is an umbrella species for conservation. This bear probably has the smallest home range and sometimes its habitat overlaps with the Asiatic black bear.

In some ways it is unlike any other bear. For example, pandas have backward facing male genitals and an "opposable thumb" called a radial sesamoid. This structure is a sixth, “toe-like” structure produced by an enlarged carpel bone. Most bears have the muscles for a radial sesamoid, but the bony extension tends to be small and insignificant. Only in the giant panda is there enough of a bone extension to use it as an opposable thumb for holding bamboo while eating.

However, the giant panda is more like other bears when comparing their genetics, blood, and immunological characteristics. Like the other bears, they have carnivore intestines, though longer than the typical meat-eater, and has the shortest digestive system of all bears. Because of these traits, they can only absorb about 20% of the food they eat. It must eat 12-15% of its body weight in bamboo, every day, for 15 hours per day in order to get enough nutrition for life. There is no evidence that the giant panda has hybridized with any other bear species.