BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Ursus arctos | Grizzly Bear 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Mating Season - breed every 2 to 3 years; May through July
Birthing Season - late November through February; one to four cubs, two
                  is common
Gestation - 6 to 7 months with delayed implantation
Age of Maturity - 5 to 8 years for females
Life Span - 25 years or more in captivity
Denning - between October and May; length of time depends on food
          availability, weather conditions, and sex of animal; may emerge
          if disturbed by human activity
[6,17,31]


PREFERRED HABITAT : 
Grizzly bear prefer open, shrub communities, alpine and low elevation
meadows, riparian areas, seeps, alpine slabrock areas, and avalanche
chutes [32,36,38].  They typically choose low elevation riparian sites,
wet meadows, and alluvial plains during spring [28,36].  During summer
and fall grizzly bear more frequently use high elevation meadows,
ridges, and open, grassy timbered sites [28,32].  Various authors have
mapped and evaluated grizzly bear habitat [5,30,35].


COVER REQUIREMENTS : 
Optimal grizzly bear cover is wooded areas interspersed with grass- and
shrubland.  Ruediger and Mealy [29] defined hiding cover as that which
is capable of hiding an animal at 200 feet (61 m) or less in an area of
30 to 50 acres (12-20 ha).  Thermal cover was defined as coniferous
trees at least 40 feet (12 m) tall with a 70 percent canopy cover in a
7- to 50-acre (3-20 ha) area.  These authors recommended maintaining 30
percent of grizzly bear habitat as cover.  McLellan [22] stated that not
enough significance is given to timbered areas as components of grizzly
bear habitat.  Graham [13] found that in Yellowstone National Park,
grizzly bear preferred open areas that were within 160 feet (50 m) of
cover.  McLellan and Shakleton [23] reported that the bears use areas
within 300 feet (100 m) of roads during the day, but that darkness is
sufficient "cover" for road use at night.  Grizzly bear use daybeds in
timbered areas that are near feeding sites [3,28].  Winter dens are
usually excavated in hillsides, although dens are also made in rock
caves, downfall timber, and beneath trees and stumps [6,31,36].


FOOD HABITS : 
Grizzly bear primarily eat grasses, forbs, roots, tubers, and fruits.
They also eat carrion, grubs, insects, particularly army cutworm moths
(Noctuidae) and ladybird beetles (Coccinelidae), fish, small rodents,
various bird species, and garbage [39].  Adult males also prey on
subordinate grizzly bear and on black bear [14].  Orchards, beehives,
and crops may be damaged by grizzly bear; they may also prey on
livestock [17,32].  Some of the more common plant foods are russet
buffaloberry (Shepherdia canadensis), Saskaton serviceberry (Amelanchier
alnifolia), Sitka mountain-ash (Sorbus sitchensis), snowberry
(Symphoricarpos spp.), hawthorne (Crataegus spp.), honeysuckle (Lonicera
spp.), whitebark pine seeds, pine (Pinaceae) vascular cambium, willow
(Salix spp.), dogwood (Cornus spp.), huckleberry and blueberry
(Vaccinium spp.), dandelion (Taraxacum spp.), sweetvetch (Hedysarum
spp.), clover (Trifolium spp.), cowparsnip (Heracleum spp.), glacier
lily (Erythronium grandiflorum), horsetail (Equisetum spp.), lomatium
(Lomatium spp.), kinnikinnick (Arctostaphylos uva-ursi), strawberry
(Fragaria spp.), buckthorn (Rhamnus spp.), paintbrush (Castelleja spp.),
thistle (Cirsium spp.), fritillary (Fritillaria spp.), boykinia
(Boykinia richardsonii), and sheathed cottonsedge (Eriophorum vaginatum)
[6,8,13,14,26,29,32,37,39].


PREDATORS : 
Grizzly bear predators include humans and other grizzly bear [17].


MANAGEMENT CONSIDERATIONS : 
Grizzly bear have a low reproductive rate and late maturation age which
makes them susceptible to overharvesting.  Also, many grizzly bear are
poached or hit by cars and trains.  Other factors contributing to the
bear's decline are habitat use and disturbance by humans, both for
commercial and recreational purposes; and fire control, which in some
instances can result in reduced acres of food-rich seral shrubfields
[17,19,33,38].  Grizzly bear have been known to prey on livestock where
their ranges overlap and occasionally kill humans as a result of chance
encounters, usually in the backcountry.  Because of conflicts between
grizzly bear and humans, grizzly bear habitat should be isolated from
developed areas, preferably in areas that receive only light
recreational, logging, or livestock use [45].

Logging can benefit grizzly bear populations if silvicultural treatments
promote berry-producing shrubs.  However, timber management effects
should be considered over the entire rotation because an increase in
shrubs may only redistribute grizzly bear and not increase their numbers
[27].  Logging can also increase human access to critical grizzly bear
habitat, disturbing populations.  Roads should be located away from
feeding areas, such as shrubfields, wet meadows, and riparian zones.
Road and seasonal trail closures must also be enforced [27,29].
Scarification and dozer pile burning can disturb soil and kill valuable
food shrubs [38].  Several authors list timber management
recommendations and road construction guidelines in grizzly bear habitat
[25,28,37,39,41].


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Ursus arctos | Grizzly Bear