Occupy a wide variety of habitats, more than any other bear species.
Dry asian steppes
Temperate rain forests
Sea level to 5,000 m (16,404 ft)
Habitat use by females with young differs from that of males.
(Rode et al 2006)
Females with young avoid areas where male bears hunt or fish;
Females may frequent areas visited by humans rather than encounter male bears;
Infanticide by males is the danger they try to avoid
Habitat use varies seasonally.
Migrate to higher elevations as plant foods become available
Shift to coastal areas and streams, when accessible, for salmon and other fish
Move to lower elevations for early berry crops, when present; then move higher to follow ripening fruits
(Craighead 1979) (Garshelis 2009) (Kurt 1990) (Pasitschniak-Arts 1993)
(Sacco and Van Valkenburgh 2004)
(Schwartz et al 2003)
Body Weight: Male 130-550 kg (287-1213 lb); Female 80-250 kg (176-551 lb) Head/Body Length: 1-2.8 m (3.3-9.2 ft) Shoulder Height: Up to 1.5 m (5 ft) Tail Length: 60-200 mm (2-8 in)
A massive bear with small, round eyes and ears, a dished-in snout, distinct shoulder hump, powerful body; only Polar Bears are heavier.
Diet largely determines size (Schwartz et al 2003)
Largest brown bears have access to meat,
Bears with vegetable diet are smaller.
Color varies from pale tan, blond, gold, many shades of brown to near black, and gray or silver. (Pasitschniak-Arts 1993)
Black and partial black fur phases in eastern and central Asia. (Garshelis 2009)
Grizzly's guard hairs often pale at tips
Underfur grown in fall and molted in spring
Males 1.2-2.2 times larger than females - extreme dimorphism.
Most likely due to competition between males during breeding season.
Other Physical Characteristics
Largest Brown Bears - Western Alaska and British Columbia; Kodiak and Admiralty Islands.
Teeth and skulls not as specialized for biting and shearing as those of many meat-eating dogs and cats. (Sacco and Van Valkenburgh 2004)
No shearing molars (carnassials)
Canine teeth long
First three premolars small or not present
Molars broad, flat
Teeth suited for wide variety of food items from insects to large ungulates
Most reliable way to distinguish a Black Bear skeleton from that of a Grizzly Bear:
Grizzly's 1st molar in lower jaw is longer than 20.4 mm (.8 in) and wider than 10.5 mm (.4 in)
Other good ways to distinguish Black and Brown Bears:
Grizzly has shoulder hump; Black Bear doesn't
Grizzly has "dished' (concave) snout that is shorter than a Black Bear's
Grizzly's ears are short and rounded; Black Bears' are larger and more pointed
Grizzly's claws are much longer.
Eyesight not keen but used for finding berries and nuts
Hearing and sense of smell acute.
Feet plantigrade (walk "flat-footed"); soles hairy
Five digits on each limb
Very long slightly curved claws 5-10 cm (2-4 in)
Claws used for digging; not well adapted for climbing trees
Female has 6 teats
Digestive tract similar to other carnivores except for its length (more surface for absorbing plant nutrients)
No fat deposits on artery walls (no arteriosclerosis); can gain significant weight in autumn (and lose in spring) with no ill effects. (Craighead 1979)
Recent studies suggest bears finely regulate calcium levels in blood and prevent its deposition in artery walls, which in turn prevents plaque build-up. (Gamble 2006)
Physiology differs from other carnivores - have a period of winter dormancy (hibernation) with profound changes in body chemistry, metabolism, breathing rate, and moderate changes in body temperature (Schwartz et al 2003)
Females with young may loose up to 43% of body mass during denning. (Garshelis 2009)
Polar-Bear/ Grizzly hybrids are fertile (Davis 1950)
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)
(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.
Interspecies Interaction (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
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
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.
DIET & FEEDING
(Hilderbrand et al 1999)
(Mattson & Merrill 2002) (Mowat & Heard 2006) (Murie 1985) (Sacco and Van Valkenburgh 2004)
(White et al 1998)
(Xu et al 2006) (Zager and Beecham 2006)
Before radio-collars and satellite telemetry use for tracking by researchers, North American bears viewed as mainly scavengers
Brown Bears are omnivores.
Recent studies show a more carnivorous diet than more omnivorous American and Asiatic Black Bears, Sun Bears, and Andean Bears. (Sacco and Van Valkenburgh 2004)
Prey typically on juvenile ungulates and small, burrowing rodents.
Extreme size difference with prey - may be up to 100 times heavier than prey
Use brute strength rather than specialized killing techniques to dispatch prey
In Mt .McKinley National Park bears ate voles, lemmings, mice, ground squirrel. (Murie 1985)
On Tibetan Plateau, eat mainly meat; pika are the prey. (Xu et al 2006)
Have the capacity to also take much larger prey such as
moose, muskoxen, caribou, elk. pronghorn, deer, bison (Murie 1985) (Craighead 1995)
(Mowat & Heard 2006)
Calves are preferred but adults sometimes taken
(Zager and Beecham 2006)
Caribou in Arctic provide significant portion of terrestrial meat (not salmon) in diet
Salmon important component of diet in Pacific coast of North America. (Mowat & Heard 2006) (Zager and Beecham 2006)
In coastal areas, salmon provide the main source (greater than 50%) of nutrients for Brown Bears.
Season in which meat is consumed determines how it is metabolized:
(Hilderbrand et al 1999)
In spring bears convert meat to lean body mass
In fall, bears convert excess protein to fat
In addition to carnivorous habits, consume a wide variety of plant and animals, seasonally available (Craighead 1995)
(White et al 1998)
Berries, Whitebark Pine seeds in Yellowstone ecosystem (important for laying on stores of fat for winter)
Sedges, grasses, horsetail (Equisetum)
Dig and eat underground stores of roots and tubers cached by mice.
Army cutworm moths (noctuids) sought on high mountain rocky slopes.
In Yellowstone region, Whitebark Pine trees currently severely threatened by disease and a warming climate; major concern for grizzly well-being.(Mattson & Merrill 2002).
Search for food with a wide variety of techniques, using "intelligence, curiosity, determination, skills, memory and endurance" (Huber 2010)
Turning over rocks
Plucking rotten logs and anthills (for ants)
Digging for tubers and invertebrates
Catching for small mammals
Stalking and capturing ungulates
After having eaten its fill, bear may cache remaining carcass by covering it with soil, sod, or rocks.
Largest bears have priority when a carcass is discovered; subordinate bears wait
REPRODUCTION & DEVELOPMENT
(Craighead et al 1995) (Kurt 1990) (Pasitschniak-Arts 1993) (Schoen 1999)
(Schwartz et al 2003)
Several males may mate with one female.
Females may mate with more than one male.
Female estrus is about 10-30 days; period is split by a short time of no receptivity.
Breeding activity occurs mid-May to July.
(Craighead et al 1995)
Lowest reproductive rate of any land mammal in North America. (Schoen
Females don't breed till 5-6 yrs.
Average of 2 cubs/litter
3-4 years between litters
In a study of Yellowstone Grizzlys, dominant males did not have sole access to estrus females.
Surprisingly, only 27.6 % of all matings observed were between alpha or beta males and females
Rest of matings were between lower-status males and females
Alpha males usually preoccupied with fighting
Alpha males spend more time checking fertility status of females (by sniffing)
Perhaps acquire access to females at the best time for fertility
Each cub in a litter can have a different father
33% of all litters studied had multiple sires.
Females have delayed implantation of embryo after fertilization
Allows for timing of birth with favorable environmental conditions.
Normally implantation is in November, around 6 weeks before birth.
Females and males enter individual dens
Females line den floor with mosses and grasses; give birth while hibernating
Reproductive biology similar to that of Black Bears.
6-7 months; occasionally 9 months (Kurt 1990)
Life Stages Birth
January-March (Schwartz et al 2003)
Most litters 2 cubs; up to 4 cubs known. (Craighead et al 1995)
Birth weight: 400-500 g (14-18 oz) (Kurt 1990)
At birth: closed eyes, little hair, helpless (altricial)
Infant (< 1 year old)
Remain with mother in den after birth
By 3 months weigh 15 kg (33 lb)
During 1st summer, young have white chest patch of fur
Young nurse 1.5 - 2.5 years.
Young may remain with mother up to 3 or 4 years.
Sexual maturity: males - 5.5 years; females - 3.5 years
Females breed at ages 3 to 8; varies depending on locality and food supply.
About 25 years. (Pasitschniak-Arts 1993)
20 yrs. in wild; 30 in captivity (Kurt 1990) but possibly 50.
A European Brown Bear born at the Leipzig Zoo, Germany lived 39 years. (Weigl
A Hokkaido Brown Bear died at 39 years at the Odawara Zoo in Japan.
A female at Yellowstone National Park gave birth to cubs at age of 22.5 years
(Craighead et al 1995)
Two years later juveniles were weaned.
Average lifespan at Yellowstone National Park is only 6 years.
Human hunters and human-caused habitat disturbances
Severe winters, malnutrition and canabalism cause some deaths
Very rarely, tigers in Russia attack bears (and vice versa)
Rarely, bears are gored by large ungulates.
Infanticide most common cause of natural death in a study of 100 bears in Sweden (Morner et al 2005)
(Huber 2010) (Itoh et al 2010) (Law & Reid 2010)
Numbers of bears in captivity needs to be managed by two-pronged focus:
Restricting captive reproduction to avoid unwanted bears
Conservation measures to enhance natural habitats
Bears in captivity need to exercise their great capacity for foraging for long periods of time; without this stimulation they are "purposeless and unchallenged." (Law & Reid 2010)
Bears in a captive environment need as much physical and mental enrichment as do primates. (Law & Reid 2010)
In a new enrichment
strategy as of 2010, 2 exhibit spaces
conncected for two young
Grizzly Bears and an elderly Manchurian
San Diego Zoo.
now take turns
the whole area.
and highly curious species benefits
from varied and new activities and
a chance to smell tracks left by
At the Ueno Zoological Gardens in Tokyo, Japan a Japanese Black Bear successfully hibernated during the winters of 2006/2007 and again in 2007/2008.
(Itoh et al 2010)
Time spent hibernating: 89 days; 68 days - within normal ranges for these bears.
Body mass decreased by 20%, a normal loss compared to bears in the wild.
This management strategy seen as enriching for the bears and of educational value for the zoo visitors
Captive-born bears should not be released into the wild. (Huber 2010)
Bears can only learn survival skills from their mother, in their natural habitat.
Only exceptions to the above: if orphaned cub had a mother for at least 6 months and the time was early summer; even so, a slim chance of survival as a free-ranging bear.
Bears seem to have fewer inherited skills and more learned skills than other carnivores
POPULATION AND CONSERVATION STATUS
(Federal Register 1975, 2007, 2010) (McLellan et al 2008) (Proctor et al 2005)
World population estimated: greater than 200,000 individuals
(Herrero 1994) (McLellan et al 2008) (Servheen 1999)
IUCN Status: Lower Risk/least concern. (1996)
CITES I in central Asia (Mongolia, China, Nepal, Bhutan)
CITES II rest of world (except Alaska)
CITES IIB for Alaskan populations
State of Alaska status: classified as 'big game"; may be legally killed by residents, no-residents, and subsistence hunters with licenses
U.S. Fish and Wildlife Endangered Species Act (Federal Register
in lower 48 states (for discussion see http://www.fws.gov/mountain-prairie/species/mammals/grizzly/)
2007 - Yellowstone population no longer meets USFW definition of threatened. (Federal Register 2007)
2009 - Yellowstone population relisted as threatened. (Federal Register 2010)
Survey work to determine numbers and distribution urgently needed in Afghanistan; currently on Afghanistan's Protected Species List.
U. S. Fish and Wildlife Service in 2000:
(Schwartz et al 2003)
Grizzly Bear Recovery Progam aims to restore grizzlys with a cooperative effort to a core widerness area of 14,983 sq km (6785 sq mi) in central Idaho and western Montana.
Threats to survival (McLellan et al 2008) (Proctor et al 2005)
Hunting by humans for sport, or unsustainable control measures.
Poaching for commercial trade in gall bladders and paws, especially in Russian Far East
North America may be next source of bear organs for medicinal uses unless belief systems change, or legal penalties provide limits to exploitation. (Servheen 1999)
Destruction and fragmentation of habitats leads to vulnerable small populations.
Causes of fragmented habitats:
Bears' attraction to areas with human foods
Factors impacting salmon survival which in turn threatens some grizzly populations:
(Mowat & Heard 2006)
Global climate change
Destruction of salmon spawning habitats (Mowat & Heard 2006)
Lack of reliable bear population estimates for sound management practices
Size of home range may require extensive cooperation between management units and countries (Herrero 1994)
Important Web Resources:
The Grizzlies of Mount McKinley: Manuscript posted by National Park Service of Grizzly Bear observations between 1922 to 1970. Includes photos, chapters on the bears interactions with humans, other carnivores, hoofed animals, rodents, birds and insects, plus food habits, behavior, mating, and raising cubs.
Grizzly Trend Monitoring: Website serves as clearinghouse of monitoring information for 6 million acres of grizzly habitat in western Montana.
Interagency Grizzly Bear Committee: Website sponsored by Montana Fish, Wildlife and Parks, the US Fish and Wildlife Service, the National Park Service, US Geological Service, USDA Forest Service, the Blackfeet Tribe, and the Confederated Salish and Kootenai Tribes. Includes downloadable tips for safety in Grizzly Bear country.
North American Bear Center: Website devoted to long-term survival of bears worldwide through publicizing scientific information about bear ecology, working to conserve bear habitats, and reducing conflict between bears and humans. Includes good book list, wide selection of downloadable videos of wild (and some captive) bear behavior.