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.
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.
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.
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.
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.
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)
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 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.
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)
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.
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)
Brown bears are important predators and seed dispersers in the ecosystems in which they live.
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)
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)
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)
Tanya Dewey (author), Animal Diversity Web.
Liz Ballenger (author), University of Michigan-Ann Arbor.
living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.
living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.
uses sound to communicate
young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.
having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends.
flesh of dead animals.
mid-altitude coastal areas with mild, rainy winters and long, dry summers. Dominant plant types are dense, evergreen shrubs.
uses smells or other chemicals to communicate
active at dawn and dusk
having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.
in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.
humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.
animals that generate their own body heat through metabolic processes.
forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.
animals that have little or no ability to regulate their body temperature, body temperatures fluctuate with the temperature of their environment, often referred to as 'cold-blooded'.
the state that some animals enter during winter in which bodily functions slow down, reducing their energy requirements so that they can live through a season with little food.
Found in northern North America and northern Europe or Asia.
offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).
makes seasonal movements between breeding and wintering grounds
having the capacity to move from one place to another.
This terrestrial biome includes summits of high mountains, either without vegetation or covered by low, tundra-like vegetation.
the area in which the animal is naturally found, the region in which it is endemic.
generally wanders from place to place, usually within a well-defined range.
an animal that mainly eats all kinds of things, including plants and animals
the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.
scrub forests develop in areas that experience dry seasons.
breeding is confined to a particular season
reproduction that includes combining the genetic contribution of two individuals, a male and a female
uses touch to communicate
this biome is characterized by large expanses of coniferous forest, there is an extended cold season and heavy snowfall.
that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).
Living on the ground.
defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement
A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.
A terrestrial biome found in very cold places -- either close to polar regions or high on mountains. Part of the soil stays frozen all year. Few kinds of plants grow here, and these are low mats or shrubs not trees. The growing season is short.
uses sight to communicate
reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.
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.