Brown Bear (Ursus arctos) Fact Sheet: Behavior & Ecology

(Pasitschniak-Arts 1993) (Garshelis 2009) (Schwartz 2003)

North American Brown Bears mostly diurnal (but active in day and night when food is scarce)

• Less active in day in areas with high human population

In Europe, mostly nocturnal due to human presence; young bears more active in day (before having negative experiences with humans)

Active at night in summer

Active season is compressed into a 5-7 month period

Often build day beds for resting in hidden places with good visibility near feeding locations (Pasitschniak-Arts 1993)
Have a yearly cycle of four main behavioral and biochemical changes

• Hibernate in winter; period varies according local climate
  • Farthest north habitats: up to 7 months
  • On Kodiak Island (mild winters) males may not even den
  • If resources are poor before hibernation time, bears may not have enough body fat to den
• After denning, for 10-14 days in "walking hibernation"
• Normal activity May - September
• Fat accumulation in fall season; food intake and weight increases significantly

(McLellan & Hovey 2001) (Pasitschniak-Arts 1993)

Home range size varies mainly with food resources. (Garshelis 2009)

• Smallest - 200 sq km (77 sq mi) for males, 100 sq km (39 sq mi) for females in coastal area with abundant food
• Largest - 8,000 sq km ( 3089 sq mi) for males in Arctic tundra
• Female home range is smaller than male

Other determinants of territory size

• Age, sex, social status, health
• Foraging habits
• Amount of cover, landscape topography, location of sleeping day beds and dens sites
• Nearness of possible mates

Brown Bears do not defend a territory.

Males and females occupy overlapping home ranges.

Young female disperse to home ranges 9.8 km (6.1 mi) from mother's home range

Males disperse up to 30 km (18.6 mi).

General

• Females with young = only lasting social bonds
• On occasion two females with young may associate and share care and nursing of young. (Murie 1985) (Craighead et al 1995)
• Orphaned cubs not adopted by another female do not survive in wild
  • Need to have at least had a mother for 6 months

 Hierarchy

• Alpha males dominate
  • Highest ranking males have best feeding sites and feeding times
• Females with cubs are willing to challenge even an alpha male

 No territory defense, but "personal space" vigorously defended by prompt attack

• Offending bear uses conciliatory posture, vocalizations to indicate no harm intended
• Mother bears with young extremely defensive; will even attack and kill a male who comes too close. (Craighead 1979).

Seasonal movements to areas with abundant food and den sites (Garshelis 2009)

• May resemble a migration as bears travel along established routes
• May travel 20 km (12 mi) in 12 hours.

Aggression (Craighead et al 1995) (Pasitschniak-Arts 1993)

• In a study of Grizzly Bears at Yellowstone National Park
  • Females display 7 times more aggressive attacks and threat behaviors towards males than towards females
  • Both male and female bears react aggressively to intrusion into their "personal space"
• No obvious (to humans) aggression by another bear triggers this response.
• Male infanticide exists, but is not a significant cause of cub mortality.
• When fighting, opponents struck in chest and shoulder with paws; bites directed towards head and neck

Play (Herrero 1985)

•  Bears of all ages play
  • Chase birds
  • Adults and young deliberately slide and roll down snowy slopes
  • Manipulate objects
• Young bears wrestle, jump and tumble together

Scent Marking

• Relies mainly on a sense of smell for information about the environment. (Pasitschniak-Arts 1993)
• Many researchers think bears do not mark a territory with scats as do many other carnivores. (Weber 1989, Craighead 1979)

Displays/Visual Signs

• Raise to full height when threatened
• Dominance indicated by a full-fronted approach
  • Neck outstretched, ears laid back, canines displayed
• Subordinance indicated by sideways orientation
  • Head low or turned away or may sit or lie down, or back away

 Vocalization (Pasitschniak-Arts 1993)

• With an attack (Kurt 1990)
  • A "high-pitched snorting with open lips"
  • A hoarse barking uttered in short bursts
  • Snap jaws together
• With a threat
  • Growl and roar
• When wounded or in pain or when hungry, lost, cold
  • Distress calls
• When contented or friendly, as a greeting, as appeasement, during courtship, between female and young.
  • Chuffing - "popping" noise made with lips and cheeks while exhaling
  • Both sexes and all ages use
    
    

Brown Bear audio, provided by BBC.

Denning

• Dens are excavated by males and females as early as September or immediately before use in November.
• Dens in dug earth have a tunnel about 4 feet long leading to a chamber 5 feet in diameter (Murie 1981)
  • Some dens have no entrance tunnel. (Garshelis 2009)
• Onset of hibernation spurred by length of day and often by a snow storm. (Servheen 1993)
• Rocky Mountains den sites:
  • Have deep snow that doesn't melt in temporary winter thaws
  • Are on steep or moderately steep slopes
  • Females and cubs may be vulnerable to snowmobile disturbance during denning and immediately after denning. (Podruzny et al 2002)
• In Croatia,
  • Dens built in rock cavities, under tree roots, in hollow trees, on the ground under conifers. (Huber & Roth 1997)
• In barren-ground habitats of Arctic regions: (McLoughlin 2002)
  • Brown bears dug dens under tall shrubs, using the roots as the den roof
  • Bears carried nesting materials to den
  • Females entered dens earlier than males
  • Both sexes are denning by October
  • Males emerge before females in late April, early May.
• During denning
  • About 1/3 of females give birth
  • Another 1/3 of denning females are still nursing yearlings (Craighead et al 1995)
• Adult females remain in a den for at least half the year. (Atkinson & Ramsay 1995) (Folk et al 1976)

(Craighead et al 1995) (Weber 1986)

• Favored gait is a slow shuffle.
• Undisturbed bear walks 5.5-6.0 km/hr (3.4-3.7 mi/hr)
• Adult bear can gallop at over 56 km/hr (35 m/hr) for 3 km (2 mi).
• Can trot with average speed of 10-12 km/hr (6.2-7.5 mi/hr)
• Tree-climbing: (Wilson & Mittermeir 2009)
  • All juvenile Brown Bears can climb trees
  • Adults in North America rarely climb trees (Black Bears do climb trees)
  • Adult Brown Bears in Europe and Asia climb trees
• Often stand while stopped
• Use trails that are shortest distance between feeding and resting areas
  • May hesitate 20 minutes while assessing an exposed area before entering open space.

(Murie 1985) (Podruzny et al 1999) (Mowat & Heard 2006)

• Grizzly bears and Brown Bears naturally adapted to exploiting temporary but abundant food items (Craighead et al 1995)
  • Feasting on whale carcasses or salmon runs are examples
  • Visiting human garbage dumps only an extenstion of this behavior
• Range overlaps that of American and Asiatic Black Bears (U. americanus, U. thibetanus)
• May compete with other carnivores for food (Pasitschniak-Arts 1993)
  • Mountain lions
  • Bobcats
  • Lynx
  • Wolves
  • Wolverines
  • Foxes
• Eagles and ravens attempt to scavenge bears' kills
  • Also may make kills because of bears' attempts to catch small rodents
• Population densities of Brown Bears in Arctic are greater when they have access to abundant caribou.
• Observations by Murie (1985) at McKinley National Park:
  • Caribou populations are culled by grizzlys - calves, old, diseased, and remains of wolf-killed carcasses all enrich Grizzly's diets.
  • Moose calves preyed upon by grizzlys; a female moose attacks bears to protect calf
  • Grizzlys rarely have an opportunity to kill Dall Sheep; carcasses of these sheep occasionally add to the grizzly diet
  • Ground squirrels often caught above ground and below, in burrows
    • Considerable effort sometimes required, lasting up to 40 minutes in one observation
• Whitebark Pine habitat vital to grizzly survival in Yellowstone National Park (Podruzny et al 1999)
  • Habitat serves as refuge.
  • Red Squirrel caches of Whitebark Pine seeds an important grizzly food resource
• A fungus, the White Pine blister rust, is decimating Whitebark Pine populations in North America.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Brown bears like to slide and roll down snowy slopes.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Craighead (1979)
Craighead et al (1995)
Garshelis (2009)
Huber & Roth (1997)
Kurt (1990)
McLellan & Hovey (2001)
McLoughlin (2002)
Murie (1985)
Pasitschniak-Arts (1993)
Servheen (1993)
Schwartz (2003)
Weber (1986)
Wilson & Mittermeir (2009)