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brown bear

Ursus arctos

What do they look like?

One of the largest of living carnivores, brown bears are 1 to 2.8 meters in length from head to rump and their tails are 65 to 210 mm long. They are 90 to 150 cm tall at the shoulder and can tower at an intimidating height of 8 feet when standing upright on their hind legs. They range in weight from 80 to more than 600 kg. On average, adult males are 8 to 10% larger than females. Brown bears are largest along the the coast of southern Alaska and on nearby islands where males average 389 kg and females average 207 kg, though some males have been weighed at as much as 780 kg. Size rapidly declines to the north and east, with individuals in southwestern Yukon weighing only 140 kg on average. Fur is usually dark brown, but varies from cream to almost black. Individuals in the Rocky Mountains have long hairs along the shoulders and back which are frosted with white, giving a grizzled appearance, hence the common name grizzly bear in that region. Brown bears are extremely strong and have good endurance; they can kill a cow with one blow, outrun a horse, outswim an Olympian, and drag a dead elk uphill.

  • Sexual Dimorphism
  • male larger
  • Range mass
    80 to 600 kg
    176.21 to 1321.59 lb
  • Range length
    1 to 2.8 m
    3.28 to 9.19 ft

Where do they live?

Brown bears once ranged throughout northern and central Europe, Asia, the Atlas mountains of Morocco and Algeria, and western North America as far south as Mexico. They are now found in extremely small numbers from western Europe and Palestine to eastern Siberia and the Himalayan region, possibly the Atlas Mountains of northwest Africa, and Hokkaido. Northern North American populations in Alaska and western Canada remain fairly stable. Many populations in the United States are now locally extinct, including those of the Sierra Nevada, southern Rockies, and Northern Mexico.

What kind of habitat do they need?

Brown bears occupy a variety of habitats, from desert edges to high mountain forests and ice fields. In North America they seem to prefer open areas such as tundra, alpine meadows, and coastlines. Historically, they were common on the Great Plains prior to the arrival of European settlers. In Siberia, brown bears occur primarily in forests, while European populations are restricted mainly to mountain woodlands. The main habitat requirement for brown bears is some area with dense cover in which they can shelter by day.

How do they reproduce?

Female brown bears mate with most of the males in the area in which they live. Males may fight over females and guard them for 1 to 3 weeks.

Mating of brown bears takes place from May to July. The young begin to develop in the mother's uterus when she enters her winter sleep. Sometime between January and March, while the mother is still sleeping through the winter, 2 to 3 young are born. Female brown bears do not mate again until their young have become independent, usually 2 to 4 years after the birth of their cubs. Brown bears become sexually mature at 4 to 6 years of age, but continue growing until 10 to 11 years old.

  • How often does reproduction occur?
    Brown bear females typically breed every 2 to 4 years.
  • Breeding season
    Breeding occurs from May to July.
  • Range number of offspring
    3 (high)
  • Average number of offspring
    2
  • Average number of offspring
    2
    AnAge
  • Range gestation period
    180 to 266 days
  • Range weaning age
    18 to 30 months
  • Range time to independence
    2 to 3 years
  • Range age at sexual or reproductive maturity (female)
    4 to 6 years
  • Range age at sexual or reproductive maturity (male)
    4 to 6 years

Young are born blind, helpless, and naked, weighing only 340 to 680 grams. By 3 months old cubs weigh about 15 kg, by 6 months weight averages 25 kg. Mothers nurse cubs for 18 to 30 months, although the cubs are eating a wide variety of other foods by about 5 months of age. Cubs remain with their mother until at least their second spring of life (usually until the third or fourth). Male brown bears do not help in raising young.

  • Parental Investment
  • no parental involvement
  • altricial
  • pre-fertilization
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female
  • extended period of juvenile learning

How long do they live?

Brown bears in the wild can live for 20 to 30 years, although most brown bears die in their first few years of life. In captivity, brown bears have been known to live up to 50 years. (Wilson and Ruff, 1999)

How do they behave?

Brown bears may be active at any time of the day, but generally forage in the morning and evening and rest in dense cover by day. Brown bears may excavate shallow depressions in which to lie. Seasonal movements of brown bears have been observed, with individuals sometimes traveling hundreds of kilometers during the autumn to reach areas of favorable food supplies, such as salmon streams and areas of high berry production.

Home ranges overlap extensively and there is no evidence of territorial defense, although bears are generally solitary. Occasionally, bears may gather in large numbers at major food sources and form family foraging groups. Under these conditions, males are dominant to females and young. The only social bonds formed are between females and young.

Brown bears begin a period of inactivity in October to December, and resums activity in March to May, with the exact period dependent on the location, weather, and condition of the individual. In southern areas, this period of inactivity is very brief or may not occur at all. This period is marked by a deep sleep in which brown bears allow their body temperature to drop by a few degrees. It is not true hibernation and bears can generally be aroused easily from their winter sleep.

Most often, brown bears dig their own dens and make a bed out of dry vegetation. Burrows are usually located on a sheltered slope, either under a large stone or among the roots of a mature tree. Dens are sometimes used repeatedly year after year.

Brown bears move with a slow, lumbering walk, although they are capable of moving very quickly and can easily catch a black bear. Brown bears are mainly terrestrial, although they can often be found swimming or preying upon fish in the water. Adults are unable to climb trees.

Home Range

Home ranges can be as large as 2,600 sq km, but are on average between 73 and 414 sq km, with male ranges nearly 7 times greater than female ranges. Home ranges overlap extensively.

How do they communicate with each other?

Brown bears communicate primarily through smells and sounds. Brown bears can be heard making moaning noises sometimes while they are foraging. They scratch and rub on trees and other landmarks to let other bears know the boundaries of their territory.

Brown bears have an excellent sense of smell (able to follow the scent of a rotting carcass for more than two miles), human-level hearing, but relatively poor eyesight. (Wilson and Ruff, 1999)

What do they eat?

Brown bears are omnivorous, eating almost anything nutritious. Their diet changes with seasonal availability of different food sources. They eat a wide variety of plant foods, including grasses, sedges, roots, moss, and bulbs. Fruits, nuts, berries, bulbs, and tubers are taken extensively during summer and early autumn. They consume insects, fungi, and roots at all times of the year and also dig mice, ground squirrels, marmots, and other fossorial animals out of their burrows. Moth larvae have been demonstrated to be especially important sources of protein and fat when brown bears are putting on fat in the fall. In the Canadian Rockies and other areas, grizzly bears (the type of brown bear in that area) are quite carnivorous, hunting moose, elk, mountain sheep, and mountain goats. Occasionally black bears are preyed upon. In Alaska, brown bears have been observed to eat carrion and occasionally capture young calves of caribou and moose. Brown bears have also been observed to feed on vulnerable populations of breeding salmon in the summer in these areas.

  • Animal Foods
  • mammals
  • fish
  • carrion
  • insects
  • Plant Foods
  • leaves
  • roots and tubers
  • seeds, grains, and nuts
  • fruit
  • bryophytes
  • Other Foods
  • fungus

What eats them and how do they avoid being eaten?

Because of their size and aggressiveness towards threats, brown bears are not often preyed upon. Humans have persecuted them throughout recent history and some cubs may be attacked by other bears or by mountain lions or wolves, although this is very rare. (Wilson and Ruff, 1999)

  • These animal colors help protect them
  • cryptic

What roles do they have in the ecosystem?

Brown bears are important predators and seed dispersers in the ecosystems in which they live.

Do they cause problems?

Brown bears have been long considered the most dangerous animal in North America, although real danger of attack from this animal is often exaggerated. In general, brown bears attempt to avoid human contact and will not attack unless startled at close quarters with young or engrossed in a search for food. They are unpredictable in temperament, however, and often exhibit impulsive and petulant behavior.

Brown bears have been persecuted extensively as predators of domestic livestock, especially cattle and sheep, although their actual impact on the livestock industry is probably negligible. (Wilson and Ruff, 1999)

  • Ways that these animals might be a problem for humans
  • injures humans
    • bites or stings

How do they interact with us?

Brown bears have been widely sought as big game trophies and are currently subject to regulated sport hunting throughout much of their range. Once brown bears were used for their meat and hides but these products are not currently in high commercial demand. Some bear body parts (such as gall bladders) bring high prices on the traditional Asian medicine market, although no true medicinal benefit of these parts has ever been documented.

Currently, brown bears help to fuel an ecotourism industry, especially in areas such as Yellowstone National Park, Wyoming and parts of Alaska. (Wilson and Ruff, 1999)

  • Ways that people benefit from these animals:
  • body parts are source of valuable material
  • ecotourism

Are they endangered?

Their conservation status depends on the population. Some populations are clearly endangered, others are not. Brown bear numbers have dropped dramatically since the turn of the century, when settlers and livestock flooded the West, driving these bears out of much of their former range. Brown bears now cling to a mere 2 per cent of their former range. Logging, mining, road construction, resorts, subdivisions, golf courses, etc. have all encroached on suitable bear habitat, resulting in a decrease in bear numbers. Brown bear numbers were estimated at 100,000 in the conterminous United States in the early 1900's, but there are now fewer than 1,000. Brown bears are still fairly common in the mountainous regions of western Canada and Alaska, perhaps numbering about 30,000 individuals. In Eurasia there are an estimated 100,000 brown bears, with about 70,000 of those living in the Soviet Union. However, habitat destruction and persecution threaten brown bears throughout their range. A growing market in bear products for the Asian market, despite a complete lack of evidence that products made from bear parts have any medical value, threatens bear species throughout Eurasia and western North America. (Wilson and Ruff, 1999)

Contributors

Tanya Dewey (author), Animal Diversity Web.

Liz Ballenger (author), University of Michigan-Ann Arbor.

References

Allen, T.B., ed. 1979. Wild Animals of North America. The National Geographic Society, Washington, D.C.

Nowak, R.M. and J.L Paradiso. 1983. Walker's Mammals of the World. 4th edition. John Hopkins University Press, Baltimore, MD.

Tubarek, G. 1993. Survivors in the Shadows: Threatened and Endangered Mammals of the American West. Northland Publishing Company, Flaggstaff, Arizona.

Wilson, D., S. Ruff. 1999. The Smithsonian Book of North American Mammals. Washington: Smithsonian Institution Press.

 
University of Michigan Museum of ZoologyNational Science Foundation

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Ballenger, L. 2002. "Ursus arctos" (On-line), Animal Diversity Web. Accessed August 01, 2014 at http://www.biokids.umich.edu/accounts/Ursus_arctos/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
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