Adult grizzly bears have a concave face, high-humped shoulders, and curved claws. Males range from 300 to 600 pounds, and females typically weigh 200 to 400 pounds. While some grizzlies have fur that looks frosted (hence, "grizzly"), their thick fur varies in color from light brown to nearly black. Distinguishing a grizzly from a black bear can be very difficult despite the grizzly's larger size, and shorter, rounder ears.
As an omnivore, the grizzly bear eats both plants and animals. Approximately 80 to 90 percent of its diet is green vegetation, nuts, seeds, berries, and roots. Grizzlies also eat insects, and they often leave behind overturned stones and rotted logs. Most of the meat in the diet comes from animal carcasses, though the grizzly will occasionally prey on elk. In Alaska and Canada, salmon is an important food source. In the Greater Yellowstone and Northern Rockies regions, grizzlies will feed predominantly on whitebark pine seeds if given a large enough source.
In the early 1800s, an estimated 50,000 grizzly bears roamed across the western United States from the Great Plains to the Pacific coast. Today, their populations in the lower 48 states are limited to the Northern Cascades (Washington), Northern Rockies, and Greater Yellowstone Ecosystems.
Under the Endangered Species Act, the U.S. Fish and Wildlife Service listed the grizzly bear as threatened in the lower 48 states in 1975. Recovery efforts have been modestly successful in some regions. In November 2005, the U.S. Fish and Wildlife Service announced its intent to establish the Greater Yellowstone grizzly bear population as a "distinct population segment (DPS)" and to remove this DPS from the List of Threatened and Endangered Wildlife.
Territories, south through British Columbia and through the western half
of Alberta. Isolated populations exist in northwestern Washington,
northern Idaho, western Montana, and northwestern Wyoming. Ursus
a. horribilis includes all brown bear of continental North
America; U. a. ssp. middendorffi includes brown bear on the Alaskan
islands of Kodiak, Afognak, and Shuyak. U. a. ssp. nelsoni's range is
in northern Mexico .
Regional Distribution in the Western United States
This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):
8 Northern Rocky Mountains
9 Middle Rocky Mountains
Occurrence in North America
Optimal grizzly bear cover is wooded areas interspersed with grass- and
shrubland. Ruediger and Mealy  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  stated that not
enough significance is given to timbered areas as components of grizzly
bear habitat. Graham  found that in Yellowstone National Park,
grizzly bear preferred open areas that were within 160 feet (50 m) of
cover. McLellan and Shakleton  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].
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].
Associated Plant Communities
more open habitats. Timbered plant communities most frequented by
grizzly bear include subalpine fir (Abies lasiocarpa)-whitebark pine
(Pinus albicaulis), lodgepole pine (P. contorta)-Douglas-fir
(Pseudotsuga menziesii), and spruce (Picea spp.)-western redcedar (Thuja
plicata)-hemlock (Tsuga spp.) forests. Sedge (Carex spp.)-bluegrass
(Poa spp.) meadows are also important, as well as shrubfields and low- and
high-elevation riparian communities [3,23,36,39].
This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):
FRES21 Ponderosa pine
FRES22 Western white pine
FRES24 Hemlock-Sitka spruce
FRES26 Lodgepole pine
FRES36 Mountain grasslands
FRES37 Mountain meadows
FRES38 Plains grasslands
Habitat: Cover Types
This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):
18 Paper birch
201 White spruce
202 White spruce - paper birch
203 Balsam poplar
204 Black spruce
205 Mountain hemlock
206 Engelmann spruce - subalpine fir
208 Whitebark pine
210 Interior Douglas-fir
212 Western larch
213 Grand fir
215 Western white pine
218 Lodgepole pine
219 Limber pine
221 Red alder
222 Black cottonwood - willow
223 Sitka spruce
224 Western hemlock
225 Western hemlock - Sitka spruce
226 Coastal true fir - hemlock
227 Western redcedar - western hemlock
228 Western redcedar
229 Pacific Douglas-fir
230 Douglas-fir - western hemlock
235 Cottonwood - willow
237 Interior ponderosa pine
251 White spruce - aspen
252 Paper birch
253 Black spruce - white spruce
254 Black spruce - paper birch
Habitat: Plant Associations
This species is known to occur in association with the following plant community types (as classified by Küchler 1964):
K001 Spruce - cedar - hemlock forest
K002 Cedar - hemlock - Douglas-fir forest
K003 Silver fir - Douglas-fir forest
K004 Fir - hemlock forest
K005 Mixed conifer forest
K008 Lodgepole pine - subalpine forest
K011 Western ponderosa forest
K012 Douglas-fir forest
K013 Cedar - hemlock - pine forest
K014 Grand fir - Douglas-fir forest
K015 Western spruce - fir forest
K018 Pine - Douglas-fir forest
K020 Spruce - fir - Douglas-fir forest
K050 Fescue - wheatgrass
K052 Alpine meadows and barren
K063 Foothills prairie
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 . Adult males also prey on
subordinate grizzly bear and on black bear . 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), Saskatoon serviceberry (Amelanchier
alnifolia), Sitka mountain-ash (Sorbus sitchensis), snowberry
(Symphoricarpos spp.), hawthorn (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)
Diseases and Parasites
Habitat-related Fire Effects
Many authors have blamed fire suppression in some areas for the decline
of grizzly bear [7,25,35,36]. Fires can promote and maintain many
important berry-producing shrubs and forbs, as well as provide a medium
for insects and in some cases carrion. Referring to the Yellowstone
National Park fires of 1988, Blanchard and Knight  stated: "The most
important apparent immediate effect of fires on grizzly bears was the
increased availability of some food items, especially carcasses of elk."
Studies in western Montana showed that spring burning in
Douglas-fir-ponderosa pine (Pinus ponderosa) types promoted huckleberry
sprouting . The number of stems present after burning were closely
related to the number present before burning. Grouse whortleberry
(Vaccinium scoparium) declined following fire in western Montana because
its shallow rhizomes were killed by the heat [37,38]. In the same study
most shrubs occurred on sites burned 35 to 70 years previously. Martin
 found that huckleberry was most productive on sites burned between
25 to 60 years previously or on sites clearcut and burned 8 to 15 years
previously. Huckleberry on sites left untreated for more than 60 years
was least productive. Other shrubs that respond well to overstory
removal and broadcast burning are elderberry (Sambucus spp.), Sitka
mountain ash, serviceberry, and buffaloberry .
Timing of Major Life History Events
Birthing Season - late November through February; one to four cubs, two
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
Date Listed: 03/11/1967
Lead Region: Mountain-Prairie Region (Region 6)
Where Listed: lower 48 States, except where listed as an experimental population or delisted
Status: Experimental Population, Non-Essential
Date Listed: 11/17/2000
Lead Region: Mountain-Prairie Region (Region 6)
Where Listed: U.S.A. (portions of ID and MT, see 17.84(l))
Status: Under Review
Lead Region: Mountain-Prairie Region (Region 6)
Where Listed: Selkirk Recovery Zone Population
Status: Under Review
Lead Region: Mountain-Prairie Region (Region 6)
Where Listed: Cabinet-Yaak Recovery Zone Population
Status: Under Review
Lead Region: Mountain-Prairie Region (Region 6)
Where Listed: North Cascades Ecosystem Recovery Zone Population
Status: Status Undefined
Lead Region: Alaska Region (Region 7)
Where Listed: Alaska
Population location: U.S.A., conterminous (lower 48) States, except where listed as an experimental population or delisted
Listing status: T
Population location: U.S.A. (portions of ID and MT, see 17.84(l))
Listing status: EXPN
For most current information and documents related to the conservation status and management of Ursus arctos horribilis , see its USFWS Species Profile
United States and Canada is available at NatureServe, although recent changes
in status may not be included.
U.S. Federal Legal Status
United States. Some popultaions in Idaho and Montana are listed as
Experimental Populations (nonessential); populations in the Cabinet-Yaak
and Selkirk zones are Candidate populations under review. Populations in
the North Cascades are also listed as Candidate populations under review .
Use of Fire in Population Management
Fire can be used to create and maintain seral shrub communities for
grizzly bear by rejuvenating shrubs, releasing nutrients, and
discouraging conifer dominance [25,37]. In the case of postharvest
treatment, many authors recommend broadcast burning and discourage dozer
pile burning. The latter method can damage rhizomes, root crowns, and
the soil [4,16,29,37,39]. Natural fire programs as well as prescribed
burning for improved grizzly habitat are encouraged and practiced by
some National Forests [7,11,16,25,35]. Garcia  and Holland 
discuss burning practices on the Kootenai and Flathead National Forests.
A fire-induced increase of berry-producing shrubs may only be beneficial
if spread over large areas that encompass home ranges of several bears
. However, prefire plant composition may dictate postfire
composition . Berry-producing shrubs must be provided continually
over time to be beneficial . Miller  recommends burning
huckleberry during spring in Montana Douglas-fir-western larch (Larix
occidentalis) communities. Also, burning should be conducted when duff
is damp; fires that remove most of the duff often reduce huckleberry
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 .
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
. 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 . Several authors list timber management
recommendations and road construction guidelines in grizzly bear habitat
Mexican grizzly bear
The Mexican grizzly bear (Ursus arctos nelsoni) is a presumed extinct subspecies of the Brown bear. It is named after American naturalist Edward William Nelson who secured a series for the U. S. Biological Survey. The holotype was shot by H. A. Cluff at Colonia Garcia, Chihuahua in 1899.
The Mexican grizzly bear was one of the heaviest and largest mammals in Mexico. It reached a length up to 183 centimetres and an average weight of 318 kilograms. Due to its silver fur it was often named "el oso plateado" (the silver bear). The Mexican grizzly bear was smaller than the grizzly bears in the United States and Canada. The general color was pale buffy yellowish varying to grayish-white, grizzled from the darker color of the underfur. Specimens in worn pelage varied to yellowish-brown and occasionally to rusty. The longest fur hairs were on the throat and the flanks. The belly was sparsely haired lacking the thick underfur of the back and the flanks.
Range and habitat
The Mexican grizzly bear inhabited the northern territories of Mexico, in particular the temperate grasslands and mountainous pine forests. Its previous range reached from Arizona to New Mexico and Mexico.
Like the rest of the brown bear subspecies, Mexican grizzly bears were omnivores. Their diet mainly consisted of plants, fruits and insects. Occasionally it fed also on small mammals and carrion. Females produced one to three cubs every three years or so.
The first Europeans to come in contact with the Mexican grizzly bear were the conquistadors in the 16th century when Francisco Vásquez de Coronado went on an expedition to find the Seven Cities of Gold. His trudge began in Mexico City in 1540 and went north to New Mexico and the Buffalo Plains in the modern-day U.S. states of Texas and Kansas. Because bears hunted the cattle from time to time they were considered a pest by farmers. The Mexican grizzly bear was trapped, shot and poisoned, and had already become scarce in the 1930s. Its former range decreased to the three isolated mountains Cerro Campana, Santa Clara, and Sierra del Nido 80 km north of Chihuahua in the state of Chihuahua. By 1960 only 30 of them were left. Despite its protected status the hunting continued. By 1964 the Mexican grizzly bear was regarded as extinct. After rumours of some surviving individuals on a ranch at the headwaters of the Yaqui River in the state of Sonora in 1968, American biologist Dr. Carl B. Koford went on a three-month survey but without success.
- Clinton Hart Merriam: Descriptions of New Bears of North America In: Proceedings of the Biological Society of Washington (1914), p.190-191.
- David Day: The Doomsday Book of Animals. Ebury Press, London
- Koford, C.B. 1969. The last of the Mexican grizzly bear. IUCN Bulletin 2:95.
- Julian Huxley, Martyn Bramwell et al.: The Atlas of World Wildlife, 1973
- David Day: The Doomsday Book of Animals. Ebury Press, London 1981, ISBN 0-670-27987-0.
- Jane Thornbark and Martin Jenkins: The IUCN Mammal Red Data Book. Part 1: Threatened mammalian taxa of the Americas and the Australasian zoogeographic region (excluding Cetacea). International Union for the Conservation of Nature, Gland Switzerland, 1982. p. 339
- Walton Beacham: World Wildlife Fund Guide to Extinct Species of Modern Times, 1997, ISBN 0-933833-40-7
- A. Starker Leopold: Wildlife of Mexico – The Game Birds and Mammals, 1959
Alaska Peninsula Brown Bear
The Alaska Peninsula brown bear is any member of the grizzly bear (Ursus arctos horribilis) that lives in the coastal regions of southern Alaska. Alaska Peninsula brown bears are a very large brown bear subspecies, usually ranging in weight from 800 to 1,200 pounds (363 to 544 kg). They are found in high densities along the southern Alaskan coast due not only to the large amount of clams and sedge grass but also to the annual salmon runs; this allows them to attain huge sizes, some of the biggest in the world. They may gather in large numbers at feeding sites, such as Brooks Falls and McNeil Falls, both in Katmai National Park near King Salmon.
There is debate as to if Alaska Peninsula brown bears should be referred to as "grizzlies" along with all other North American subspecies of the brown bear. There is confusion experienced when referring to inland and coastal ones separately, but biologists still maintain that coastal ones are truly brown bears. However, it is considered correct to place all North American members of U. arctos in the subspecies horribilis except the giant Kodiak bears of Kodiak Island. To avoid confusion, many simply refer to all North American members, including Kodiaks, as "grizzly bears."
Prized by hunters for their skulls and hides, up to 500 of Alaska's 1,500 brown bears killed yearly by hunters come from the Alaska Peninsula. To hunt this great bear, hunters must follow a variety of regulations, including bear bag limits, hunting fees, and proper rifles.
Naming and etymology
The Alaska Peninsula brown bear's name most likely arose because, until 1975, they were considered a different species from the inland grizzly bear. They were never considered closer to European brown bears than inland grizzlies, but were given a different name, due to the size and color differences of coastal browns and inland grizzlies. From 1975 onward, they were considered to be the same species, but coastal ones retained the name "brown bear."
Alaska Peninsula brown bears are the second largest type of brown bear in the world, only after the giant bears of Kodiak Island. They usually measure 8 feet (2.4 m) in length, usually have a shoulder height of about 4-4-1/2 feet (1.2-1.4 m), and a hindfoot length of 11 in (28 cm). One study found that the average weight for a coastal male was around 408 kilograms (900 lb). For a female, this average weight would be 227 kilograms (500 lb). On the other hand, an occasional huge male brown has been recorded which greatly exceeds ordinary size, with weights reported up to 680 kg (1,500 lb). A large coastal male of this size may stand up to 3 metres (9.8 ft) tall on its hind legs and be up to 1.5 metres (4.9 ft) at the shoulder. Although variable from blond to nearly black, grizzly bear fur is typically brown in color with white tips. A pronounced hump appears on their shoulders; the hump is a good way to distinguish a black bear from a grizzly bear, as black bears do not have this hump.
Brown bears on the Alaskan Peninsula usually feed on spawning salmon, and use many different ways to catch them. These include waiting at the bottom of the falls for the fish to jump, or standing at the top of the falls waiting to catch the fish in midair (sometimes in their mouths). Bears also have much experience at chasing fish around and pinning the slippery animals with their claws. After the salmon runs, berries and grass make the mainstay of the bears' diets, after which they put on sufficient fat reserves and go into hibernation.
- McLellan, B. N., Servheen, C. & Huber, D. (2008). "Ursus arctos". IUCN Red List of Threatened Species. Version 2013.1. International Union for Conservation of Nature. Retrieved 2013-10-05.
- "Brown Bear". Alaska Department of Fish and Game.
- Whitaker, John O. (1980). The Audubon Society Field Guide to North American Mammals. ISBN 0-394-50762-2.
- "Mammalian Species- Ursus arctos" (PDF). American Society of Mammalogists, Smith College. Retrieved 2012-06-14.
- "Brown or Grizzly Bear". North American Bear Center.
- "Grizzly Bear". National Wildlife Federation.
- "Brown Bear Research in Alaska". ADFG.
- "Brown Bear". Bear Trust International.
- Wood, G. The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc (1983), ISBN 978-0-85112-235-9
- "Kodiak Bear Fact Sheet". Alaska Department of Fish and Game. Retrieved 2008-10-27.
- Species Profile: Grizzly bear (Ursus arctos horribilis). U.S. Fish and Wildlife Service. Ecos.fws.gov. Retrieved on 2012-08-17.
The grizzly bear (Ursus arctos horribilis), also known as the silvertip bear, the grizzly, or the North American brown bear, is a subspecies of brown bear (Ursus arctos) that generally lives in the uplands of western North America. This subspecies is thought to descend from Ussuri brown bears which crossed to Alaska from eastern Russia 100,000 years ago, though they did not move south until 13,000 years ago.
Except for cubs and females, grizzlies are normally solitary, active animals, but in coastal areas, the grizzly congregates alongside streams, lakes, rivers, and ponds during the salmon spawn. Every other year, females (sows) produce one to four young (commonly two) which are small and weigh only about 500 grams (1 lb). A sow is protective of her offspring and will attack if she thinks she or her cubs are threatened.
The word "grizzly" in its name refers to "grizzled" or grey hairs in its fur, but when naturalist George Ord formally named the bear in 1815, he misunderstood the word as "grisly", to produce its biological Latin specific or subspecific name "horribilis".
Most adult female grizzlies weigh 130–200 kilograms (290–440 lb), while adult males weigh on average 180–360 kilograms (400–790 lb). The average total length in this subspecies is 198 centimetres (6.50 ft), with an average shoulder height of 102 centimetres (3.35 ft) and hindfoot length of 28 centimetres (11 in). Newborn bears may weigh less than 500 grams (1 lb). In the Yukon River area, mature female grizzlies can weigh as little as 100 kilograms (220 lb). On the other hand, an occasional huge male grizzly has been recorded which greatly exceeds ordinary size, with weights reported up to 680 kilograms (1,500 lb). Although variable from blond to nearly black, grizzly bear fur is typically brown in color with white tips. A pronounced hump appears on their shoulders; the hump is a good way to distinguish a black bear from a grizzly bear, as black bears do not have this hump.
Brown bears are found in Asia, Europe and North America giving them one of the widest ranges of bear species. The ancestors of the grizzly bear originated in Eurasia and travelled to North America approximately 50,000 years ago. This is a very recent event in evolutionary time, causing the North American grizzly bear to be very similar to the brown bears inhabiting Europe and Asia.
In North America, grizzly bears previously ranged from Alaska to Mexico and as far east as the Hudson Bay area. In North America, the species is now found only in Alaska, south through much of western Canada, and into portions of the northwestern United States including Idaho, Montana, Washington and Wyoming, extending as far south as Yellowstone and Grand Teton National Parks, but is most commonly found in Canada.
In Canada, there are approximately 25,000 grizzly bears occupying British Columbia, Alberta, the Yukon, the Northwest Territories, Nunavut and the northern part of Manitoba. Combining Canada and the United States, grizzly bears inhabit approximately half the area of their historical range. In British Columbia, grizzly bears inhabit approximately 90% of their original territory. There were approximately 25,000 grizzly bears in British Columbia when the European settlers arrived. However, population size significantly decreased due to hunting and habitat loss. In 2008, it was estimated there were 16,014 grizzly bears. Population estimates for British Columbia are based on hair-snagging, DNA-based inventories, mark-recapture and a refined multiple regression model.
Other provinces and the United States may use a combination of methods for population estimates. Therefore, it is difficult to say precisely what methods were used to produce total population estimates for Canada and North America, as they were likely developed from a variety of studies. The grizzly bear currently has legal protection in Mexico, European countries, some areas of Canada and in the United States. However, it is expected that repopulating its former range will be a slow process, due to a variety of reasons including the reintroduction of competing predators to these areas, the effects of reintroducing such a large animal to areas prized for agriculture and livestock, and due to the bear's slow reproductive habits. There are currently about 55,000 wild grizzly bears located throughout North America.
Brown bears (of which the grizzly bear is a subspecies) can live up to 30 years in the wild, though 20 to 25 is normal.
Grizzly bears have one of the lowest reproductive rates of all terrestrial mammals in North America. This is due to numerous ecological factors. Grizzly bears do not reach sexual maturity until they are at least five years old. Once mated with a male in the summer, the female delays embryo implantation until hibernation, during which miscarriage can occur if the female does not receive the proper nutrients and caloric intake. On average, females produce two cubs in a litter and the mother cares for the cubs for up to two years, during which the mother will not mate. Once the young leave or are killed, females may not produce another litter for three or more years, depending on environmental conditions. Male grizzly bears have large territories, up to 4,000 square kilometres (1,500 sq mi), making finding a female scent difficult in such low population densities.
Although grizzlies are of the order Carnivora and have the digestive system of carnivores, they are normally omnivores, since their diet consists of both plants and animals. They have been known to prey on large mammals, when available, such as moose, deer, sheep, elk, bison, caribou, and even black bears. Grizzly bears feed on fish such as salmon, trout, and bass, and those with access to a more protein-enriched diet in coastal areas potentially grow larger than interior individuals. Grizzly bears also readily scavenge food on carrion left behind by other animals.
Canadian or Alaskan grizzlies are larger than those that reside in the American Rocky Mountains. This is due, in part, to the richness of their diet. In Yellowstone National Park in the United States, the grizzly bear's diet consists mostly of whitebark pine nuts, tubers, grasses, various rodents, army cutworm moths and scavenged carcasses. None of these, however, match the fat content of the salmon available in Alaska and British Columbia.
Although the diet of grizzly bears varies extensively based on seasonal and regional changes, plants make up a large portion of their diet, with some estimates as high as 80–90%. Various berries constitute an important food source when they are available. These can include blueberries, blackberries (Rubus fruticosus), salmon berries (Rubus spectabilis), cranberries (Vaccinium oxycoccus), buffalo berries (Shepherdia argentea), and huckleberries (Vaccinium parvifolium), depending on the environment. Insects such as ladybugs, ants and bees are eaten if they are available in large quantities. In Yellowstone National Park, it has been observed that grizzly bears may obtain half of their yearly caloric needs by feeding on Miller moths that congregate on mountain slopes. When food is abundant, grizzly bears will feed in groups. For example, many grizzly bears will visit meadows right after there has been an avalanche or glacier slide. This is due to an influx of legumes, such as Hedysarum, which the grizzlies consume in massive amounts. When food sources become scarcer, however, they separate once again.
In preparation for winter, bears can gain approximately 400 lb (180 kg), during a period of hyperphagia, before going into false hibernation. The bear often waits for a substantial snowstorm before it enters its den: such behaviour lessens the chances that predators will find the den. The dens are typically at elevations above 1,800 metres (5,900 ft) on north-facing slopes. There is some debate amongst professionals as to whether grizzly bears technically hibernate: much of this debate revolves around body temperature and the ability of the bears to move around during hibernation on occasion. Grizzly bears can "partially" recycle their body wastes during this period. In some areas where food is plentiful year round, grizzly bears skip hibernation altogether.
Most notable in Yellowstone have been the interactions between gray wolves and grizzly bears. With the reintroduction of gray wolves to Yellowstone, many visitors have witnessed a once common struggle between a keystone species, the grizzly bear, and its historic rival, the gray wolf. The interactions of U. arctos horribilis with the wolves of Yellowstone have been under considerable study. Typically, the conflict will be in the defense of young or over a carcass, which is commonly an elk killed by wolves. The grizzly bear uses its keen sense of smell to locate the kill. Then, the wolves and grizzly will play a game of cat and mouse. One wolf may try to distract the bear while the others feed. The bear then may retaliate by chasing the wolves. If the wolves become aggressive with the bear, it is normally in the form of quick nips at its hind legs. Thus, the bear will sit down and use its ability to protect itself in a full circle. Rarely do interactions such as these end in death or serious injury to either animal. One carcass simply is not usually worth the risk to the wolves (if the bear has the upper hand due to strength and size) or to the bear (if the wolves are too numerous or persistent).
Black bears generally stay out of grizzly territory, but grizzlies may occasionally enter black bear terrain to obtain food sources both bears enjoy, such as pine nuts, acorns, mushrooms, and berries. When a black bear sees a grizzly coming, it either turns tail and runs or climbs a tree. Black bears are not strong competition for prey because they have a more herbivorous diet. Confrontations are rare because of the difference in size, habitat, and diet of the bear species. When this happens, it is usually with the grizzly being the aggressor. The black bear will only fight when it is a smaller grizzly such as a yearling or when the black bear has no other choice but to defend itself.
The segregation of black bear and grizzly bear populations is possibly due to competitive exclusion. In certain areas, grizzly bears outcompete black bears for the same resources. For example, many Pacific coastal islands off of British Columbia and Alaska support either the black bear or the grizzly, but rarely both. In regions where both species coexist, they are divided by landscape gradients such as age of forest, elevation and openness of land. Grizzly bears tend to favor old forests with high productivity, higher elevations and more open habitats compared with black bears.
The relationship between grizzly bears and other predators is mostly one-sided; grizzly bears will approach feeding predators to steal their kill. In general, the other species will leave the carcasses for the bear to avoid competition or predation. Any parts of the carcass left uneaten are scavenged by smaller animals. Cougars, however, generally give the bears a wide berth. Grizzlies have less competition with cougars than with other predators, such as coyotes, wolves, and other bears. When a grizzly descends on a cougar feeding on its kill, the cougar usually gives way to the bear. When a cougar does stand its ground, the cougar will use its superior agility and its claws to harass the bear, yet stay out of its reach until one of them gives up.
Coyotes, foxes, and wolverines are generally regarded as pests to the grizzlies rather than competition, though they may compete for smaller prey, such as ground squirrels and rabbits. All three will try to scavenge whatever they can from the bears. Wolverines are aggressive enough to occasionally persist until the bear finishes eating, leaving more than normal scraps for the smaller animal.
The grizzly bear has several relationships with its ecosystem. One such relationship is a mutualistic relationship with fleshy-fruit bearing plants. After the grizzly consumes the fruit, the seeds are dispersed and excreted in a germinable condition. Some studies have shown germination success is indeed increased as a result of seeds being deposited along with nutrients in feces. This makes grizzly bears important seed distributors in their habitats.
While foraging for tree roots, plant bulbs, or ground squirrels, bears stir up the soil. This process not only helps grizzlies access their food, but also increases species richness in alpine ecosystems. An area that contains both bear digs and undisturbed land has greater plant diversity than an area that contains just undisturbed land. Along with increasing species richness, soil disturbance causes nitrogen to be dug up from lower soil layers, and makes nitrogen more readily available in the environment. An area that has been dug by the grizzly bear has significantly more nitrogen than an undisturbed area.
Nitrogen cycling is not only facilitated by grizzlies digging for food, it is also accomplished via their habit of carrying salmon carcasses into surrounding forests. It has been found that spruce tree (Picea glauca) foliage within 500 m (1,600 ft) of the stream where the salmon have been obtained contains nitrogen originating from salmon on which the bears preyed. These nitrogen influxes to the forest are directly related to the presence of grizzly bears and salmon.
Grizzlies directly regulate prey populations and also help prevent overgrazing in forests by controlling the populations of other species in the food chain. An experiment in Grand Teton National Park in Wyoming in the United States showed removal of wolves and grizzly bears caused populations of their herbivorous prey to increase. This, in turn, changed the structure and density of plants in the area, which decreased the population sizes of migratory birds. This provides evidence grizzly bears represent a keystone predator, having a major influence on the entire ecosystem they inhabit.
Conflicts with humans
Grizzlies are considered by some experts to be more aggressive than black bears when defending themselves and their offspring. Aggressive behavior in grizzly bears is favored by numerous selection variables. Unlike the smaller black bears, adult grizzlies are too large to escape danger by climbing trees, so they respond to danger by standing their ground and warding off their attackers. Increased aggressiveness also assists female grizzlies in better ensuring the survival of their young to reproductive age. Mothers defending their cubs are the most prone to attacking, being responsible for 70% of fatal injuries to humans. Historically, bears have competed with other large predators for food, which also favors increased aggression.
Grizzly bears normally avoid contact with people. In spite of their obvious physical advantages and many opportunities, they almost never view humans as prey; bears rarely actively hunt humans. Most grizzly bear attacks result from a bear that has been surprised at very close range, especially if it has a supply of food to protect, or female grizzlies protecting their offspring. In such situations, property may be damaged and the bear may physically harm the person.
Exacerbating this is the fact that intensive human use of grizzly habitat coincides with the seasonal movement of grizzly bears. An example of this spatiotemporal intersection occurs during the fall season: grizzly bears congregate near streams to feed on salmon when anglers are also intensively using the river. Some grizzly bears appear to have learned to hone in on the sound of hunters' gunshots in late fall as a source of potential food, and inattentive hunters have been attacked by bears trying to appropriate their kills.
Increased human-bear interaction has created "problem bears", which are bears that have become adapted to human activities or habitat. Aversive conditioning, a method involving using deterrents such as rubber bullets, foul-tasting chemicals or acoustic devices to teach bears to associate humans with negative experiences, is ineffectual when bears have already learned to positively associate humans with food. Such bears are translocated or killed because they pose a threat to humans. The B.C. government kills approximately 50 problem bears each year and overall spends more than one million dollars annually to address bear complaints, relocate bears and kill them.
For back-country campers, hanging food between trees at a height unreachable to bears is a common procedure, although some grizzlies can climb and reach hanging food in other ways. An alternative to hanging food is to use a bear canister.
The grizzly bear is listed as threatened in the contiguous United States and endangered in parts of Canada. In May 2002, the Canadian Species at Risk Act listed the Prairie population (Alberta, Saskatchewan and Manitoba range) of grizzly bears as being wiped out in Canada. As of 2002, grizzly bears were listed as Special Concern under the COSEWIC registry and considered threatened under the U.S. Fish and Wildlife Service.
Within the United States, the U.S. Fish and Wildlife Service concentrates its effort to restore grizzly bears in six recovery areas. These are Northern Continental Divide (Montana), Yellowstone (Montana, Wyoming, and Idaho), Cabinet-Yaak (Montana and Idaho), Selway-Bitterroot (Montana and Idaho), Selkirk (Idaho and Washington), and North Cascades (Washington). The grizzly population in these areas is estimated at 750 in the Northern Continental Divide, 550 in Yellowstone, 40 in the Yaak portion of the Cabinet-Yaak, and 15 in the Cabinet portion (in northwestern Montana), 105 in Selkirk region of Idaho, 10–20 in the North Cascades, and none currently in Selway-Bitterroots, although there have been sightings. These are estimates because bears move in and out of these areas, and it is therefore impossible to conduct a precise count. In the recovery areas that adjoin Canada, bears also move back and forth across the international boundary.
The U.S. Fish and Wildlife Service claims the Cabinet-Yaak and Selkirk areas are linked through British Columbia, a claim that is disputed.
All national parks, such as Banff National Park, Yellowstone and Grand Teton, and Theodore Roosevelt National Park have laws and regulations in place to protect the bears. Even so, grizzlies are not always safe in parks. In Glacier National Park in Montana and Banff National Park in Alberta, grizzlies are regularly killed by trains as the bears scavenge for grain that has leaked from poorly maintained grain cars. Road kills on park roads are another problem. The primary limiting factors for grizzly bears in Alberta and elsewhere are human-caused mortality, unmitigated road access, and habitat loss, alienation, and fragmentation. In the Central Rocky Mountains Ecosystem, most bears have died within a few hundred meters of roads and trails.
On 9 January 2006, the US Fish and Wildlife Service proposed to remove Yellowstone grizzlies from the list of threatened and protected species. In March 2007, the U.S. Fish and Wildlife Service "de-listed" the population, effectively removing Endangered Species Act protections for grizzlies in the Yellowstone National Park area. Several environmental organizations, including the NRDC, brought a lawsuit against the federal government to relist the grizzly bear. On September 22, 2009, U.S. District Judge Donald W. Molloy reinstated protection due to the decline of whitebark pine tree, whose nuts are a main source of food for the bears. In 1996 the International Union for Conservation of Nature moved the grizzly bear to "Lower Risk Least Concern" status on the IUCN Red List.
Farther north, in Alberta, Canada, intense DNA hair-snagging studies on 2000 showed the grizzly population to be increasing faster than what it was formerly believed to be, and Alberta Sustainable Resource Development calculated a population of 841 bears. In 2002, the Endangered Species Conservation Committee recommended that the Alberta grizzly bear population be designated as threatened due to recent estimates of grizzly bear mortality rates that indicated the population was in decline. A recovery plan released by the Provincial government in March 2008 indicated the grizzly population is lower than previously believed. The Provincial government has so far resisted efforts to designate its declining population of about 700 grizzlies (previously estimated at as high as 842) as endangered.
Environment Canada consider the grizzly bear to a "special concern" species, as it is particularly sensitive to human activities and natural threats. In Alberta and British Columbia, the species is considered to be at risk. In 2008, it was estimated there were 16,014 grizzly bears in the British Columbia population, which was lower than previously estimated due to refinements in the population model.
Conservation efforts have become an increasingly vital investment over recent decades, as population numbers have dramatically declined. Establishment of parks and protected areas are one of the main focuses currently being tackled to help reestablish the low grizzly bear population in British Columbia. One example of these efforts is the Khutzeymateen Grizzly Bear Sanctuary located along the north coast of British Columbia; at 44,300 hectares (109,000 acres) in size, it is composed of key habitat for this threatened species. Regulations such as limited public access, as well as a strict no hunting policy, have enabled this location to be a safe haven for local grizzlies in the area. When choosing the location of a park focused on grizzly bear conservation, factors such as habitat quality and connectivity to other habitat patches are considered.
The Refuge for Endangered Wildlife located on Grouse Mountain in Vancouver is an example of a different type of conservation effort for the diminishing grizzly bear population. The refuge is a five-acre terrain which has functioned as a home for two orphaned grizzly bears since 2001. The purpose of this refuge is to provide awareness and education to the public about grizzly bears, as well as providing an area for research and observation of this secluded species.
Another factor currently being taken into consideration when designing conservation plans for future generations are anthropogenic barriers in the form of urban development and roads. These elements are acting as obstacles, causing fragmentation of the remaining grizzly bear population habitat and prevention of gene flow between subpopulations (for example, Banff National Park). This, in turn, is creating a decline in genetic diversity, and therefore the overall fitness of the general population is lowered. In light of these issues, conservation plans often include migration corridors by way of long strips of "park forest" to connect less developed areas, or by way of tunnels and overpasses over busy roads. Using GPS collar tracking, scientists can study whether or not these efforts are actually making a positive contribution towards resolving the problem. To date, most corridors are found to be infrequently used, and thus genetic isolation is currently occurring, which can result in inbreeding and therefore an increased frequency of deleterious genes through genetic drift. Current data suggest female grizzly bears are disproportionately less likely than males to use these corridors, which can prevent mate access and decrease the number of offspring.
Trophy hunting causes an imbalance between the male and female sexes, since older males are primarily sought to be hunted for their size. The hunting of older males creates a gender imbalance within an area specific population. The killing of older male bears in their own territory allows other males to migrate in and claim the late bear's territory. Older male bears will have had cubs with existing female bears in the region. This may cause the newly migrated male bear to become potentially infanticidal towards cubs of the resident females and the late male bear.
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Names and Taxonomy
horribilis. North American subspecies of brown bear include :
Ursus arctos arctos, brown bear
Ursus arctos horribilis, grizzly bear
Ursus arctos stickeenensis
Ursus arctos nelsoni, Mexican grizzly bear, possibly extinct
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