bear, in zoology

Introduction

bear, large mammal of the family Ursidae in the order Carnivora, found almost exclusively in the Northern Hemisphere. Bears have large heads, bulky bodies, massive hindquarters, short, powerful limbs, very short tails, and coarse, thick fur. They walk on the entire sole of the foot and normally move with a slow, ambling gait. However, they are capable of moving with great speed when necessary and some achieve bursts of 35 mi (56 km) per hour. Most bears can climb trees and swim well. They stand on the hind feet to reach objects with their paws. They have large, strong, non-retractile claws, used for catching prey and for digging. Their teeth are adapted to grinding as well as tearing. Nearly all species are omnivorous, feeding on fruits, roots and other plant matter, honey, carrion, insects, fish, and small mammals.

Adult bears are solitary except during the mating season. Groups may feed together where quantities of food are available, but there is little social contact. In cold climates bears sleep through most of the winter in individual dens made in caves or holes in the ground. This sleep is not a true hibernation, as the bear's metabolism remains in a normal state and it may wake and emerge during warm spells. The young, usually twins, are born during winter in a very immature state. Cubs stay with their mothers for about a year, and females usually mate only every other year. Bears are not generally subject to predation, unless they are in a weakened condition. A bear is a formidable adversary and may attack a human if it is injured or startled.

Classification

Bears are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Carnivora, family Ursidae.

Types of Bears

The brown bear of Eurasia, Ursus arctos, is extinct in much of Western Europe, but small numbers survive in some wooded sections of that region and larger numbers in Russia and N Asia. The Russian variety was the bear most often trained to dance and box in circuses and shows in the past.

The Asian black bear, or moon bear, Selenarctos thibetanus, is found in forests from central Asia and the Himalayas to Japan. The sun bear, Helarctos malayanus, is found in tropical forests of SE Asia. Smallest of the bears, it is about 4 ft (120 cm) long and weighs about 100 lb (45 kg). It spends much time in trees and is fond of honey; it is sometimes called honey bear (a name also applied to the kinkajou). The sloth bear, Melursus ursinus, is a medium-sized bear of the forests of S India and Sri Lanka.

The North American brown bears, including the Kodiak bear and grizzly bear, are regarded by many authorities as varieties of U. arctos. Brown bears are dish-faced; i.e., their muzzles curve upward in profile. Their shoulders are humped. They range in color from yellow-brown to nearly black, with much color variation among different varieties, local populations, and individuals. Most varieties do not climb well. The Kodiak bear, or big brown bear, is the largest living member of the Carnivora, sometimes reaching a length of 9 ft (2.7 m), a shoulder height of 41⁄2 ft (140 cm), and a weight of over 1,600 lb (730 kg). It is found along the south coast of Alaska and, like the Siberian brown bear, eats large numbers of salmon during salmon runs.

The most widespread and numerous North American bear is the so-called black bear, U. americanus, found in Alaska, Canada, the Great Lakes region, mountainous areas of the United States, and on the Gulf Coast. American black bears range in color from light brown to black; in northern regions there are gray and nearly white forms. Their muzzles are always cinnamon brown and are straight in profile. They are further distinguished from brown bears by their smaller size and by their hindquarters, which are higher than their shoulders. Males are usually about 6 ft (190 cm) long and weigh about 500 lb (230 kg).

The polar bear, U. maritimus, is an almost exclusively carnivorous species of the Arctic. The only bear of the Southern Hemisphere is the spectacled bear, Tremarctos ornatus, of the Andes Mts.; it is so called from the light-colored circles around its eyes. Recent genetic evidence has led to the classification of the giant panda, Ailuropoda melanoleuca, in the bear family as well.

Bibliography

See R. Perry, Bears (1970).

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