Bear Species
Brown Bear
( Ursus arctos )

Brown bear (Ursus arctos)

Physical description and lifespan

Brown bears range in size from 1.8 to 2.2 m in length. Adult males weigh almost 500 kg in the most productive habitats, with adult females weighing from 150 kg to slightly over 200 kg. The species is characterised by its size, a large mass of muscle overlying the scapulae (shoulder hump) and long fore claws, measuring 10 cm.

Although Eurasian brown bears typically have a uniform coat colour, the colouring of brown bears is actually quite variable, ranging from very light blond to almost black. Brown bears in the Rocky Mountains of North America may have guard hairs with a white or silver tip and a white band near the end of their bodes, giving a ‘frosted’ appearance. Brown bear cubs and yearlings often have white or cream-colored neck markings that disappear on most individuals as they mature.

Human-induced mortality is the main factor affecting the lifespan of adult brown bears in the wild (in the few areas where human mortality is low, bear-bear mortality increases). While they may live up to 25–30 years (with females naturally living longer than males) in areas where human activity is low, natural mortality is high in cubs and sub-adult bears.

Distribution

Brown bears have the broadest distribution of any bear species – they are found in habitats ranging from the Gobi desert in Mongolia to the rainforests of coastal British Columbia and Alaska’s arctic tundra, where they may overlap with polar bears.

Behaviour

Brown bears are solitary, except as consort pairs, family groups or when grouped around food resources. The species is not territorial but does maintain a hierarchal system dominated by large adult males and females. Brown bears are active during daylight hours and also at night in areas where human activity levels are high.

Reproduction

The brown bear mating season is between late April and mid-July, with estrus (the period during which females are willing to mate) typically lasting 10–30 days. The fertilized egg begins development immediately, but then becomes dormant for several months before implanting in the uterine wall in late October or early November.

Pregnant females deliver one to four cubs while hibernating in January or February. Brown bear cubs usually remain with their mothers for about 18 months in Europe and Asia, while cubs in North American are dependent on their mothers for an additional year or two. Litter size and intervals vary in brown bear populations depending on habitat quality and genetics.

Diet

Brown bears are omnivorous and feed on a wide variety of food. They are known to feed extensively on animal matter ranging in size from insects to large ungulates (hoofed mammals), such as deer. Brown bears are effective predators, particularly of infant ungulates, but will also scavenge carcasses when the opportunity presents itself.

Although as much as 50–60 per cent of their diet may be composed of animal matter, brown bears readily feed on plant material including grasses and forbs in spring and soft and hard mast crops (berries and nuts) in summer and autumn.

Conflict with humans

Brown bears have been involved in conflict with humans throughout their range: attacking people and livestock, competing with people for ungulates, raiding crops and feeding on rubbish in and around rural communities and industrial enterprises such as logging, mining and oil and gas extraction.

The wide distribution of brown bears brings them into contact with people in a variety of circumstances:

Europe and Asia: Brown bear attacks on domestic sheep, the destruction of beehives and raids on agricultural crops and fruit orchards are all major sources of conflict with humans.

Eastern Europe: As brown bear populations expand, conflicts are developing around waste management in some communities.

Hokkaido Island, Japan: Damage to agricultural crops by brown bears and problems associated with the inadequate disposal of refuse have been reported.

North America: Fear of attacks on people dominates the perception of brown bears across much of their range, particularly in the United States. Most of the rare human attacks are associated with defensive behaviours (bears surprised or crowded that are protecting their young or a food source), which may result from the increasing overlap in bear habitat and human leisure activity and hunting ranges. Non-defensive attacks are even rarer and have sometimes been associated with bears that have learned to feed on human food and garbage.

2010 conservation status

Brown bears are classified as ‘LR’ (lower risk) on the IUCN 2010 Red List; populations in many parts of the world are reasonably secure as a result of management efforts to stabilise or increase their numbers.

However, brown bears are a conservation dependent species and without active management can be expected to meet the IUCN criteria for an endangered or vulnerable species within the next five years.

The fear of attacks on humans by brown bears – real or imagined – coupled with concern about attacks on livestock have played a significant role in limiting efforts to increase their distribution in North America and Europe. High levels of mortalities caused by humans have affected conservation efforts in many parts of the world.

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