BEARS: Ursidae

PHYSICAL CHARACTERISTICS

Bears have big heads, round ears, small eyes that face forward, very short tails, and stocky legs. They are plantigrade, walking on the heels and soles of their feet like humans do. Each paw has five curved claws that are not retractable, or cannot be pulled back.

Bears come in many colors, from the familiar black, brown, and white to blonde, cinnamon, and blue-gray. Some have a yellow, orange, or white chest marking in the form of a patch, a letter V or U, or a short horizontal line. Spectacled bears are called "spectacled" because of the light markings around their eyes. Among Malayan sun bears, the smallest species, males are 4 to 5 feet (1.2 to 1.5 meters) long and weigh between 60 and 150 pounds (27 and 70 kilograms). In comparison, male polar bears on average are 8 to 9 feet (2.4 to 2.7 meters) long and weigh 900 to 1,300 pounds (400 to 590 kilograms). Females, or sows, of all species are usually smaller than males, or boars.

GEOGRAPHIC RANGE

Spectacled bears are found in Bolivia, Colombia, Ecuador, Peru, and Venezuela. Brown bears live in the United States, Canada, Europe, and Asia. American black bears inhabit the United States, Mexico, and Canada. Malayan sun bears, sloth bears, and Asiatic black bears thrive in Asia. Giant pandas live in China, while polar bears occupy the Arctic regions.

HABITAT

Bears live in a variety of habitats. For example, spectacled bears can be found in the dense rainforests of South America, and Malayan sun bears thrive in tropical rainforests in Southeast Asia, while polar bears live on the Arctic tundra.

DIET

Bears are generally omnivores, eating both plants and animals. However, the polar bear is almost entirely carnivorous, eating mainly ringed seals, while the giant panda lives exclusively on bamboo. The sloth bear favors termites and ants. The other species, while preferring plant sources, also eat young animals and fish.

BEHAVIOR AND REPRODUCTION

Bears maintain a solitary lifestyle, living alone, except when mating and rearing their young. When food is plentiful, they share but keep their personal space. Bears are usually crepuscular (active at dawn and dusk). Their excellent memory enables them return to past food sources. They are agile tree climbers and fast runners, reaching speeds of up to 30 miles per hour (48 kilometers per hour). Polar bears and Asiatic black bears are expert swimmers.

Most bears mate during spring or summer, but the fertilized egg undergoes delayed implantation, during which it takes up to six months to attach to the uterus and start developing. As a result, cubs are born tiny, ranging in weight from about 11 ounces (325 grams) in sun bears to 21 ounces (600 grams) in polar and brown bears. Most sows have two cubs, although some have as many as five. Depending on the species, cubs may stay with their mothers for one to more than four years.

SURVIVING IN THE ARCTIC

The polar bear has a dense underfur next to its skin and a water-repellent outer fur, called guard hairs. The hairs are clear, hollow tubes that conduct sunlight to the black skin, where heat is absorbed. The clear tubes reflect sunlight, making the outer coat appear white. Blending in with the whiteness of the ice and snow, the polar bear can easily sneak up on its prey. The hollow hairs also keep the bear afloat when swimming. A thick layer of blubber, or fat, further insulates the body from the cold. Compact ears also prevent heat loss. Fur-covered feet serve as snowshoes, while thickly padded soles provide traction against slippage on ice.

BEARS AND PEOPLE

People hunt some bear species for meat and trophies. Some Asian cultures use bear parts to treat diseases. In addition, many zoos house bears as exhibit animals.

CONSERVATION STATUS

The giant panda is considered Endangered, facing a very high risk of extinction, or dying out, in the wild. The spectacled, sloth, and Asiatic black bears are considered Vulnerable, facing a high risk of extinction in the wild. These and other bear species are threatened by declining populations due to losing habitat, as humans clear more land for agriculture, mining, and other activities.

AMERICAN BLACK BEAR (Ursus americanus;): SPECIES ACCOUNTS

Physical characteristics: Although most American black bears are black, some are brown, cinnamon, blue-gray, or even white. Siblings (brothers and sisters) may have different colors. Some bears have a white chest marking. They stand about 5 feet (1.5 meters) tall. Males weigh about 250 to 350 pounds (110 to 160 kilograms), almost twice as much as females (150 to 175 pounds, or 70 to 80 kilograms).

Geographic range: American black bears are found in the United States, Mexico, and Canada.

Habitat: American black bears thrive in forested regions, wetlands, and meadows. They range in the frozen tundra (treeless plain) of

Alaska and Labrador, Canada. They are also found around campsites and other places where human food and garbage are available.

Diet: American black bears are mostly herbivores, preferring berries, fruits, grasses, and roots. With strong claws, they dig up insects in the ground and pry open honeycombs. In the absence of plant food, they eat fish, young birds, and small mammals. They also feed on carrion (dead and decaying flesh) and campsite leftovers.

Behavior and reproduction: American black bears are active at dawn and dusk, sleeping or resting most of the day and night. They are, however, adaptable, adjusting their schedule to mate or to avoid humans or predators (animals that hunt them for food). Skillful tree climbers, they scale tree trunks with their curved claws to escape predators, such as timber wolves and grizzly bears. Except for mothers and cubs, these bears are loners, although they may feed close together at an abundant food source. From late spring to early summer, adults breed for a few days, then go their separate ways. On average, two cubs are born in mid-winter. They remain with their mothers for up to two years.

American black bears and people: People hunt American black bears for meat and trophies. Poachers, or illegal hunters, kill the animals for body parts believed to have healing powers. The bears very rarely attack humans, although they may become aggressive in places where human food is found. Some bears damage cornfields and beehives.

Conservation status: American black bears are not in danger of extinction (dying out). ∎

GIANT PANDA (Ailuropoda melanoleuca): SPECIES ACCOUNTS

Physical characteristics: Giant pandas are white, with black fur around the eyes and on the ears, shoulders, chest, and legs. Each front paw has six toes, the last toe functioning as a thumb. Actually an extension of the wrist bone, the oversized thumb helps the panda grasp bamboo stems. Powerful jaws and large molar teeth help grind the tough bamboo.

Giant pandas have bigger heads and shorter legs than other bears. Adults are about 5.5 to 6 feet (1.7 to 1.8 meters) in body length. Males weigh about 175 to 280 pounds (80 to 125 kilograms), and females weigh about 155 to 220 pounds (70 to 100 kilograms).

Geographic range: Pandas are found in southwestern China.

Habitat: Giant pandas live in mountainous bamboo forests.

Diet: The giant pandas' diet consists almost entirely of bamboo. Occasionally they eat bulbs and small animals, such as bamboo rats and musk deer fawns.

Behavior and reproduction: Although giant pandas mostly live alone, they communicate through different sounds, including squeals, honks, and snorts. They share community scent-marking areas, sending messages through anal-genital secretions rubbed on surfaces. They also use urine to mark tree trunks, with the males doing so on handstands for higher markings. Giant pandas mate during spring. Sows give birth to twins half of the time, but usually only one cub survives when two are born.

Giant pandas and people: Giant pandas are major attractions in zoos around the world. In addition, their endangered status has made them symbols for conservation.

Conservation status: The giant panda is Endangered, driven from its habitat by human activities, such as deforestation, or the clearing of land, for farming. The panda cannot reproduce fast enough to recover its losses. Females mate only in the spring and within just a two-to-three-day period. Only one cub survives, and the mother waits up to three years to mate again. ∎

POLAR BEAR (Ursus maritimus): SPECIES ACCOUNTS

Physical characteristics: Polar bears, the largest land carnivores, have a thick white or yellowish coat, a long body and neck, black nose, and small eyes and ears. The front paws, webbed like a duck's feet, function as paddles for swimming. The long, sharp claws are used for grasping and killing prey. On average, adult males weigh about 900 to 1,300 pounds (400 to 590 kilograms) and stand 8 to 9 feet (2.4 to 2.7 meters). Adult females weigh about 450 to 600 pounds (200 to 270 kilograms) and stand 6 to 7 feet (1.8 to 2.1 meter).

Geographic range: Polar bears live in the icy Arctic Ocean and in the countries that extend into the ocean: United States (Alaska), Canada, Russia, Norway, and Greenland (a territory of Denmark).

Habitat: Polar bears prefer the Arctic pack ice, formed when big pieces of thick ice are frozen together. In summer, when the ice melts, they live on land, staying close to the water.

Diet: Polar bears eat mainly ringed seals and occasionally bearded seals. They also prey on walruses and belugas. In warmer months, they hunt ducks and rabbits, as well as feed on mussels, berries, and kelp, a brown seaweed.

Behavior and reproduction: Polar bears mostly keep to themselves but do not defend a particular home territory. They gather on shore to share beached whales and walruses. A bear may share its food with another if the latter begs submissively through body language, such as nodding its head. Polar bears are very tidy, washing themselves in the ocean after meals.

Polar bears mate in the spring. In the fall, after stuffing herself with food, the pregnant sow digs a den in deep snow and hibernates while awaiting childbirth. Cubs that are born in winter nurse until spring, with the mother living off the fat storage in her body. Cubs stay with their mothers for at least two and a half years.

Polar bears and people: Once hunted as trophies and for their fur and meat, polar bears are now protected by the laws of the five countries where they live.

Conservation status: Some scientists believe that, within a hundred years, polar bears may become extinct if Earth's temperature continues to rise. Warmer temperatures cause more arctic ice to melt, preventing the bears from hunting their primary food source, the ringed seals, on the sea ice. ∎

FOR MORE INFORMATION

Books:

Busch, Robert H. The Grizzly Almanac. New York: The Lyons Press, 2000.

Craighead, Lance. Bears of the World. New York: Voyageur Press, 2000.

Lumpkin, Susan, and John Seidensticker. Smithsonian Book of Giant Pandas. Washington, D.C. and London, England: Smithsonian Institution Press, 2002.

Patent, Dorothy Hinshaw. A Polar Bear Biologist at Work. New York: Grolier Publishing, 2001.

Periodicals:

Conover, Adele. "Sloth Bears: They Eat Ants, but Take On Tigers." Smithsonian (January 2000): 88–95.

Fair, Jeff. "When Bears Go Fishing." Ranger Rick (June 2001): 38–39.

Kleiman, Devra G. "Giant Pandas: Bamboo Bears." ZooGoer 21, no. 2 (1992) Online at http://nationalzoo.si.edu/Publications/ZooGoer/1992/2/giantpandasbamboobears.cfm (accessed on June 15, 2004).

Morrison, Jim. "The Incredible Shrinking Polar Bears." National Wildlife 42, no. 2 (2004) Online at http://www.nwf.org/nationalwildlife/article.cfm?articleId=880&issueId=66 (accessed on June 15, 2004)

Zoffka, Kennda. "Sleeping with the Bears." Odyssey (January 2002): 38–39.

Web sites:

American Zoo and Aquarium Association Bear Advisory Group. "Bear species." The Bear Den.http://www.bearden.org/species.html (accessed on June 15, 2004).

"Black Bears." National Park Service, Big Bend National Park. http://www.nps.gov/bibe/teachers/factsheets/blackbear.htm (accessed on June 15, 2004).

Sea World Education Department. "Polar Bears." SeaWorld/Busch Gardens Animal Information Database. http://www.seaworld.org/infobooks/PolarBears/home.html (accessed on June 15, 2004).