[BEARS: Imagination and Reality.  At the San Diego Natural History Museum from October 21, 2000 through January 2, 2001.]

Teacher's Guide: Background Information

Bears

Bears are remarkable creatures, both in imagination and in reality. But bears make up only several of the more than 15,000 species of mammals in the world. Humans, bears, bats, dogs, and cats are all mammals. Like all mammals, bears are born alive, nurse their young, and have hair (fur) on their bodies. Additionally, bears have five toes on each paw; small ears on large heads; strong, pointed teeth; bulky bodies; relatively short, but powerful legs; and short tails. Bears communicate with blowing noises, huffs, and roars. They usually walk on four legs, but can walk upright for short distances on their hind legs. Different species of bears have different eating habits. Black bears and grizzly bears are omnivorous—they eat both plants and animals. Polar bears are carnivorous—they eat animals. Panda bears are herbivorous—they eat plants.

Bears of the World

There are eight species of bears in the world. Polar bears are yellowish-white and live throughout the Arctic. The spectacled bears—named for the black or blackish-brown circles and semicircles of white around their eyes—are the only bears in South America. Sun bears, the world's smallest bears, are still found in the lowland forests of southeast Asia, but their present numbers are not known. They have black fur with an orange or whitish breast mark. Sloth bears have shaggy black hair with a yellow-white Y- or V-shaped chest mark, and live in the forested areas south of the Himalayas and in Sri Lanka. Asiatic black bears, sometimes called moon bears because of a white crescent-shaped mark on the chest, live throughout much of southern Asia. Panda bears, noted for their distinctive eye patches, live along the eastern edge of the Tibetan plateau. Although it is also called a bear, the koala bear is actually a marsupial, like kangaroos and opossums.

The BEARS: Imagination and Reality exhibit and this background information focus on the remaining two species: the black bear and the grizzly (or brown) bear. Black bears are found in most Canadian provinces; the rocky Mountains, the upper Midwest, the eastern and western parts of the United States; and northern Mexico. Grizzly bears are found in western Canada, Alaska, Wyoming, Montana, Idaho, and Washington. In addition, scientists now group the European brown bear in the same species as the grizzly. In some places the ranges of black bears and grizzly bears overlap.

Physical Characteristics

Grizzly bears are sometimes black, but they can also be beige, cinnamon, red, blond, or a mixture of these colors. Grizzly bear fur may have silvery tips giving it a grizzled look. In addition, to their grizzled fur tips, they have a distinguishing hump between their head and upper back. Grizzlies tend to be larger than black bears. Their faces and ears are more rounded and they have long, sharp claws. If encountered, they usually are more aggressive than black bears and generally are more difficult to scare away.

Black bears are not necessarily black; they may be brown, cinnamon, beige, white and even blue. This makes identification difficult in areas where both grizzlies and black bears exist. However, in general, black bears are smaller than grizzlies and have more elongated faces. Their ears are larger and more pointed and their claws are shorter. They do not have the prominent hump behind the shoulder area found on grizzlies. Their fur never has the silvery tips that give grizzlies their name.

Habitat

Habitats are places where animals (or plants) live that provide an animal's basic needs of space, food, shelter, and water. Bears need plenty of space. Food should be reliable and plentiful throughout the late spring, summer, and early fall. If an adequate supply of food is not available during this time, bears may starve unless they seek food elsewhere. Bears adapt to winter food shortages by entering a period of seasonal lethargy (dormancy). Bears can obtain water from rivers, ponds, lakes, or streams. They need materials and sites for their daybeds and dens. Trees, bushes, and branches provide materials for daybeds. Bears use thickets, hollow logs, depressions left by uprooted trees, rocky outcroppings, and even open areas as den sites.

The precise habitats in which bears live depends on what is available. Grizzlies prefer oak woodlands, river valleys, and open meadows. Black bears prefer mixed hardwood forests with some open areas like fields and meadows which provide grasses, herbs, berries, and other desirable foods.

Food and Feeding Habits

Both black bears and grizzly bears are omnivorous. On average they obtain more than 70% of their calories from plants because plants are more readily available than animals. When bears do eat animals, they usually eat dead, rotting flesh because it is difficult for bears to pursue and kill healthy deer, elk, or moose. Also, the food that grizzly bears and black bears eat depends upon the season and location. Generally, bears eat whatever is most easily available.

In general, when grizzly bears emerge from their dens in the spring, they feed mainly on newly sprouted grasses. In the early summer when grasses mature and become hard to digest, grizzlies eat roots and tubers. They also eat the carcasses of animals, if available. They will consume vast quantities of fish, especially salmon, if they can obtain them. In the fall, grizzlies eat more in preparation for winter lethargy.

When black bears emerge from their dens in the spring, they feed on newly sprouted grasses like the grizzlies. When grasses mature in early summer, black bears will eat whatever berries are ripe. If fish are extremely plentiful (e.g., at a salmon stream), black bears will gorge themselves. Like grizzlies, black bears eat the carcasses of other animals when they find them. In late summer as berry crops decline, black bears add fat by gorging on ripe nuts such as acorns or pine nuts.

Winter Lethargy (winter dormancy)

Both black bears and grizzly bears spend the winter in a dormant or sleeping state. Both of these bears live in climates with cold winters when food sources are limited and travel in deep snow is difficult. In late summer and early fall, these bears find suitable den sites. They choose new den sites every year, usually within the same territory. Once they choose a site, they prepare their den by pulling in nearby plant materials such as grass and evergreen boughs for bedding. Bears usually enter their dens by late October or early November. Depending upon the weather, bears spend five to seven months in their dens. While this dormant period is often referred to as hibernation, it differs from true hibernation in several ways. In true hibernation, an animals body temperature drops to a few degrees above freezing and if disturbed it takes a couple of hours to wake up. A sleeping bear's body temperature is somewhat lower than normal, but not as low as true hibernators. During winter sleep, bears are alert and easily aroused. True hibernators (e.g., ground squirrels, marmots) rouse themselves several times during the winter to eliminate body wastes. Bears, on the other hand, do not urinate or defecate during their winter sleep.

Reproduction

Although bears mate in early June, the fertilized eggs do not implant until fall, just before their winter sleep. If a female is not sufficiently nourished with enough stored fat to sustain herself and her possible offspring, the fertilized eggs do not implant and her pregnancy terminates.

If she is sufficiently well nourished, the eggs implant and the pregnancy continues. While still in a dormant state, she gives birth and cares for one to four nearly hairless cubs, each weighing less than one pound. She nurses the cubs, keeps them warm, and cleans them. The cubs grow quickly, but stay close to their sleeping mother. When they emerge from the den in early spring they weigh between four and ten pounds. The mother continues to nurse them until late fall as she teaches them to climb trees, to react to danger, and to forage and hunt for food. At the end of the cubs' second winter, the mother sends them out to fend for themselves and establish their own territories.

Introduction

Exhibit Overview

Background Information

Vocabulary

At the Museum

Pre- and Post-visit Activities

Bibliography

bear drawing

Locomotion

Bears and humans share a common type of locomotion, called plantigrade locomotion. They walk flat on the foot/paw with their heel, sole, and pad on the ground. This broad base of support (compared to hoofed animals, for instance), combined with their ability to balance their bodies over their rear legs, gives bears and humans greater stability in an upright position and allows humans to walk upright easily. Bears, although they usually walk on all four paws, can walk upright on their hind legs. If brush or ground cover is in their pathway, they may stand upright to get a better view of their surroundings or to see or hear better. They may also stand upright when they claw trees, fence posts, or utility poles, or to display aggression when they encounter another bear.

Because bears and humans walk in the same way, they leave similar prints. Both bear paw prints and human footprints show a sole, heel, and a pad as well as five toes. However, there are identifiable differences. For instance, the large toe is on the outside of the bear paw print, but on the inside of the human footprint. Although bears have claws and humans have toenails, the toenails do not show in a human footprint. Bears' claws show as small holes above the toe in a paw print, but the holes made by the claws of grizzly bears are more striking than those of black bears because grizzlies have longer claws. (See bear tracks.)

Although bears can walk upright, they only do so for short distances and are slow. They normally walk on all four paws. Although they look bulky, clumsy, and slow when down in this position, bears can run swiftly, reaching speeds up to 30 miles per hour. Humans cannot outrun bears. However, bears can only run this fast for short distances. Other animals such as healthy adult deer and elk can usually outrun a bear if they have a good enough start.

Encounters and Management

If bears are to continue to exist, people must learn how to share the land and how to ensure their own safety. Because both grizzlies and black bears are solitary animals who usually avoid humans, attacks by either are rare. However, on rare occasions they have attacked people, sometimes fatally. People should know where bears are likely to be, the kinds of foods bears eat, the signs of bears nearby, and the differences between black and grizzly bears. Black bears are usually less aggressive and less dangerous. However, when in bear country, people should adopt an alert and respectful attitude toward all bears. Statistically, bears are in much greater danger from people than people are from bears. (See If you Encounter a Bear.)

In North America in the early 1900s, bears were still plentiful, numbering about 100,000. They roamed throughout much of North America outside settled areas. No laws restricted hunting until bear populations had declined greatly. Other factors also caused the decline. Human populations grew and people used more land, encroaching on bear habitats. Grizzly bears were especially threatened. In 1975, Congress enacted the Endangered Species Act requiring that grizzlies be carefully managed by the various state and federal offices including monitoring hunting, camping, and other human activities in grizzly habitat areas. The federal act does not protect black bears, but states still regulate hunting to ensure their survival.

drawing of front bear paw

left front paw

Other Views of the Bear

Bear's power, intelligence, and similarities to humans have led to a rich body of myths and legends in many cultures. Portrayals of bears in both scientific and fictional literature suggest that the bear is perhaps the most anthropomorphized of all animals.

Ancient Greeks had many stories and legends about bears. One explains the origins of the Big Bear (Ursa Major) and the Little Bear (Ursa Minor) constellations. Several involve gods and goddesses. One ancient folk observation explains the meaning of a common phrase. When some ancient Greeks observed female bears licking newborn cubs, they assumed that the bears were born like shapeless lumps of clay which their mothers shaped into being. For centuries people believed that bears could sculpt both life and behavior. To this day parents still warn their children that they may "get a licking" if they don't "shape up."

Bear legends and rituals are important to many Native American peoples. Eastern and Northern Woodland groups have traditionally revered and honored the black bear. Plains Indians have long believed that the grizzly bear's power could cure illness and protect warriors in battle. The bear has been an important symbol of power for Native Americans of the southwestern United States. Bear designs are found on pottery and carved bear fetishes. Native peoples of the Northwest Coast decorated housefronts, totem poles, plates, bowls, storage boxes, canoes, and blankets with bear designs. Bear masks and bear rattles are used in dances reenacting ancient myths and legends which vividly portrayed the interaction of people, supernatural creatures, bears, and other animals. Hunters and warriors of some Native American cultures sought to emulate the awesome strength and courage of the grizzly.

Human-like bears are commercially successful. The warmhearted and innocent Winnie the Pooh behaves much like a child. British author A. A. Milne was inspired by the nursery experiences of his son Christopher Robin to write Winnie the Pooh in 1926. Smokey the Bear was created by the U.S. Forest Service in 1944 as part of a campaign to prevent forest fires. As protector of the wilderness, he exemplifies many human traits. Yogi Bear and Boo-Boo, created by Hanna Barbera Productions in the late 1950s, mix traits of humans and black bears. Unlike real bears, however, these Jellystone Park bears pose no danger to people, even while stealing campers' "pikanic baskets." The Care Bears and the Bernstein Bears are even newer creations. The teddy bear inspired by Teddy Roosevelt remains popular today.

Conclusion

Whether through cartoons, fairy tales, or cultural traditions, most people are familiar with some aspects of bears. Bears also are important because they form a part of the natural ecosystem. Research on bear hibernation may shed light on problems ranging from kidney failure to bone deterioration in the elderly and in astronauts on long space flights. Someday this research my lead to new treatments for cardiovascular disease and obesity.







diagram of spring star chart

Teacher's Guide | Bears | Exhibits