Distribution and density of brown bears in Alaska

Most of Alaska from sea level to approximately 1,500m elevation is occupied brown bear habitat (Figure 5.2). The subspecies horribilis occurs from Unimak Island, on the Aleutian chain, throughout mainland Alaska, to Alaska’s north slope bordering the Arctic Ocean. Brown bears occur in the riparian corridors along the lower Yukon and Kuskokuim Rivers. A few wandering bears are occasionally found in the wetland delta habitat between these rivers but this area is not considered brown bear habitat (Figure 5.2). In Prince William Sound, they occur on Montague, Hinchinbrook, Hawkins, and Kayak Islands.

In southeastern Alaska, brown bears are abundant on Admiralty, Chichagof, Baranof, and Kruzof Islands but are absent from the more southern islands of Prince of Wales, Kupreanof, Etolin, and adjacent islands; a few wandering brown bears are occasionally found on Mitkof and Wrangell islands which are close to the mainland. In southeastern Alaska, black bears (U. americanus) and
wolves (Canis lupus) occur on the large southern islands not occupied by brown bears (including Mitkof and Wrangell) but not on the northern islands occupied by brown bears. This distribution may reflect post glacial dispersal of brown bears from the north and by black bears from the south following retreat of Pleistocene glaciers (Klein 1963). Black bears, wolves, and brown bears are sympatric in many portions of interior Alaska.

The distribution of brown bears in Alaska appears to have remained relatively unchanged since European and Russian exploration during the mid-1700s (Figure 5.2). Brown bear densities vary greatly in different regions of Alaska. Density estimates conducted using standardized techniques (Miller et al. 1987) throughout Alaska reveal densities >175 bears/1,000km² in the coastal populations of the Alaska Peninsula, Kodiak and Afognak Islands, and the northern islands of southeastern Alaska (Figure 5.2) (Miller et al. in prep.). Approximately 50% of Alaska’s brown bear population occurs in these high density populations which represents about 8.5% of the brown bear habitat in the state (Figure 5.2). It appears likely that these high densities are supported in large part by abundant runs of up to five species of Pacific salmon (Oncorhynchus spp.) and lush plant and fruit resources found in these warmer maritime environments. Bears in these high density portions of the Alaskan coast are larger and generally darker than bears from interior and arctic regions of Alaska. These size and color differences have resulted in coastal bears being commonly called “brown” bears while the smaller and usually lighter-colored interior bears are called “grizzlies”.

Densities less than 40 bears/1,000km² have been reliably estimated in the portions of interior Alaska without access to abundant salmon runs (Figure 5.2) (Miller et al. in prep.). These estimates range from 6.8/1,000km² on the coastal flatlands and adjacent foothills of the northeastern Brooks Range (Reynolds and Garner 1987) to 34 bears/ 1,000km² in Denali National Park (Dean 1987). These low density habitats represent about 84% of the brown bear’s distribution in Alaska (Figure 5.2). Approximately 41% of Alaska’s brown bear population lives in these low density habitats.

Intermediate densities of 40–175 bears/1,000km² are thought to occur in small areas of south-central Alaska near the coast and on the mainland in southeastern Alaska. These areas represent approximately 7.5% of Alaska’s bear habitat and contain about 9% of the population (Figure 5.2). The classification of these areas as intermediate in density is based on subjective impressions; bear densities have not been directly measured in any of these areas.

There is no precise estimate on the number of brown bears in Alaska. During the period 1985–1992, however, information on brown bear density was estimated in 15 Alaskan study areas using standardized capture-mark-recapture techniques (Miller et al. in press). Density estimates using other techniques were available in four other areas (Miller et al. in press). In 1993, biologists from
the Alaska Department of Fish and Game were asked to make subjective extrapolations from these density estimates to obtain population estimates for each of the 26 game management units in Alaska (Miller 1993). Biologists were also asked to subjectively estimate minimum and maximum numbers for their areas based on the reference density values. This resulted in an estimate of 31,700 bears in Alaska with a lower limit of 25,000 and an upper limit of 39,100 (Miller 1993). This estimate is lower than previous estimates for Alaska (Peek et al. 1987) not because bear populations have declined, but because of improved information on bear densities.

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Distribution and density of brown bears in Canada

The status of brown bears in Canada was reviewed by Macey (1979) and more recently by Banci (1991). Macey concluded that brown bears were not endangered or threatened but were extremely vulnerable. Because Canada is a large and diverse country and brown bears are distributed over approximately 3,470,000km² (2.4 times the size of the state of Alaska) Banci (1991) decided that an analysis of their status required dividing the country into 14 “brown bear zones” based on similar climate, land forms, and human activities. The status of brown bears in the zones is closely linked to the number and distribution of people. In inhospitable areas of the north or in the rugged mountains,
there are limited human settlements and brown bears are relatively numerous for the habitat, while brown bears are relatively rare where people have settled.

Estimating bear numbers is notoriously difficult. Without an intensive marking program, only estimations based on largely subjective information and extrapolation from research areas are available (Table 5.3). Banci (1991) estimated that about 25,000 brown bears live in Canada and this number has unlikely changed significantly in the past few years. In two of the brown bear zones, the Non-Mountainous Boreal Plains and the Glaciated Prairies, brown bear have been extirpated. In the Hot Dry Plateaus, brown bears are rare and considered threatened. The status of brown bears in the remaining zones are often debated; some people suggest that they are vulnerable while others believe they are doing fine.

 

 

Arctic Coastal Plains: An estimated 2,860 brown bears occur in this zone. Although there have been some sightings on Banks and Victoria Island, these bears are mostly limited to the mainland. This zone is sparsely populated by people and there is little road access. Impacts on bears occur near settlements and petroleum exploration and development have had a significant impact in localized areas. Over most of the area, brown bears are likely near carrying capacity.

Taiga Shield: The status of brown bears in this region is poorly known but an estimate of 790 was provided by Banci (1991). The bear habitat is thought to be relatively poor on the Taiga Shield. There are no known recent records of brown bears from northern Manitoba or Saskatchewan. This zone has few human residents and bear kills are rare.

Taiga Plains: The bear habitat in this zone is also inferior and, although density estimates are poor, a total population of 1,520 bears has been estimated. This zone has few residents and access remains poor.

Subarctic Mountains: There are an estimated 2,540 brown bears in the Subarctic Mountains and this population has been hunted since 1965. The productivity of the population is low and hunting regulations are consequently strict. Access is limited in the zone and there are few human settlements.

Subarctic Mountains and Plains: The density of brown bears in this zone appears higher than the more northern and eastern areas. A total of 5,680 bears are estimated to live here. There are three major highways crossing this area and there are a few communities with more than 2,000 people. Poor garbage management has resulted in bear deaths and many translocations. Mining and petroleum are the major industries in this zone. Hunting mortality associated with big game guiding is the major source of bear mortality.

Cold Boreal Plains: Agricultural development has eliminated brown bears from a portion of this zone, however, an estimated 970 bears remain. Natural gas development is the major industry although the amount of forestry, in particular pulp production, is rapidly increasing. Access developed by the various industries is becoming a significant problem for brown bears. Human settlements are rare; however, there are three communities with over 4,000 people.

Cold Moist Mountains: This zone is relatively good bear habitat and has an estimated population size of 2,940 brown bears. Forestry, mining, and big game hunting are the major industries. Human settlements are rare and small in this zone and although access is currently limited, it is rapidly increasing in certain locations.

Temperate Wet Mountains: Some of the most productive brown bear habitat in the country occurs here. Vancouver, the largest city in western Canada, is located in the southern tip of this zone and the influence of such a large settlement has greatly affected brown bear numbers in this corner of the country. The southern coast supports about 90 brown bears which is only 5% of its estimated capability. There are few settlements in the north coast and access is generally difficult. Range fragmentation is a concern in the southern portion. Poor management of garbage and other attractants has resulted in bear deaths and many translocations. Although timber harvest and trophy hunting are very extensive in the north coast, an estimated 3,210 brown bears inhabit the area.

Cool Moist Plateaus: Cattle ranching is extensive in portions of this zone and intolerance of large carnivores has significantly impacted brown bear numbers. Due to the generally flat topography, timber harvest is highly mechanistic and extensive. There are several large and many small communities in this zone and road access is extensive. Poor management of garbage and other attractants has resulted in bear deaths and many translocations. The estimated number of bears in this zone is 1,100.

Cool Moist Mountains: This zone has some very productive bear habitat but there is also much rock and ice. A variety of human activities and in particular forestry, hydroelectric developments, and hunting have had a significant impact on bears in this area. Range fragmentation is a concern along transportation corridors. There are several towns of between 5–20,000 people and access is extensive. Poor management of garbage and other attractants has resulted in bear deaths and many translocations. Banff, Jasper, Glacier, and Mt. Revelstoke NPs are in this zone and although some very productive habitat occurs in these parks, as a whole, they are relatively poor for bears and support only about 250 of the estimated 2,540 brown bears in this zone.

Hot Dry Plateaus: For brown bears, this is a relatively unproductive zone and, when combined with extensive areas of human settlement, agriculture, forestry, mining, recreation, and extensive access, only about 140 brown bears remain. Most of these bears occur along the border of the Wet Temperate and Cool Moist Mountains. Range fragmentation is a serious concern.

Cool Dry Mountains: This zone has some very productive brown bear habitat but poor habitat is also common. Human activities are varied and brown bears have been impacted by agriculture, forestry, mining, hunting, and recreation. There are numerous small communities, and several with more than 5,000 people. Poor management of garbage and other attractants has resulted in bear deaths and many translocations. Access is widespread. Range fragmentation is a serious concern. There are an estimated 930 brown bears in this zone.

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Historic range and current distribution in lower 48 United States

The grizzly bear (Ursus arctos horribilis) formerly occurred in at least 16 states of the western United States as late as the year 1800 (Figure 5.4). Its distribution began to change in response to excessive human-caused mortality and habitat loss in the early 1800s. The grizzly was considered
a predator and a competitor of humans by the settlers who occupied the American West. As such it was shot, poisoned, and killed wherever it was found. It is estimated that there were approximately 50,000 grizzly bears south of Canada in 1800 (USFWS 1993).

Grizzly bears occupied a variety of habitats prior to the attempted extermination by Europeans. Grizzlies were found across the great plains east of the Rocky Mountains where they were dependent upon the millions of bison (Bison bison) that inhabited the prairies. Early accounts (DeVoto 1953) remark on the abundance of grizzly bears along the Missouri River in present-day Montana, USA. These bears were apparently attracted to the river by hundreds of drowned bison carcasses and the riparian zone foods such as shrubs. These carcasses resulted from mass drowning when hundreds of thousands of bison crossed the river. The grizzly was also distributed across the Rocky Mountains from northern areas in Montana and Idaho (Moore 1996) south to Arizona and New
Mexico (Brown 1985). Grizzly bears were probably more abundant in California than any other state (Storer and Tevis 1955). Grizzly bears fed on salmon in California rivers, on beached whales along the coast and on the abundant mast crops of California oaks. Grizzly bears were so much a part of California that the grizzly was placed on the state flag, the only state to do so. Nevertheless, grizzly bears were shot, poisoned and trapped in California as in the rest of the western United States. The last wild grizzly bear in California was killed in 1922, leaving the only grizzly bear remaining in California the symbolic bear on the state flag.

By the 1920s and 1930s, only 100 years after the arrival of European settlers, grizzly bears were being driven to extinction throughout much of their range. At this time, domestic sheep were a large agricultural interest that spread far into the mountains in the last refuges of the grizzly bear. Places that are now wilderness such as areas of the Bob Marshall and Scapegoat Wilderness in Montana and the Selway-Bitterroot Wilderness in Idaho were filled with herds of domestic sheep. The maintenance of domestic sheep in areas with grizzly bears and wolves (Canis lupus) required predator control techniques such as trapping and poisoning. By 1922 the range had been dramatically reduced and grizzlies were only present in isolated mountain areas. This was a reduction of approximately 75% in less than 100 years. By 1922 the range of the grizzly was a series of isolated populations which, because of their isolation, were more vulnerable to extinction.

The 1920s and 1930s saw the lowest numbers of grizzly bears surviving south of Canada. In portions of the present-day Sun River Game Preserve in Montana, a place now rich in grizzly bears, an entire summer of searching for bear tracks only turned up one or two. Hunting and killing of bears for protection of livestock continued into the 1970s. Of the 37 populations present in 1922, 31 were eliminated by 1975. By 1975 grizzlies had been reduced to 7–800 in less than 2% of the former range. Five separate populations remained in the four states of Wyoming, Montana, Idaho, and Washington (Figure 5.4, Table 5.6). The only refuge for grizzlies were the two National Parks, Yellowstone Park in Wyoming, Montana, and Idaho, and Glacier Park in Montana. Of these five populations, four were contiguous with larger populations across the Canadian border.

It was thought in 1975 that grizzly bears still remained in the Bitterroot Mountains of Idaho and Montana. Investigations since 1975 have found no evidence that grizzly bears remain in this area. The last bear verified in the Bitterroots was in the early 1940s. In 1979 an adult female grizzly bear was killed by a hunter in the San Juan Mountains of southwest Colorado. This was the first grizzly bear seen in the area in decades. Following this find, two years of intensive research failed to document any verified evidence of grizzly bears in the San Juans. It seems likely that the bear killed by the hunter was the last remnant bear in this area more than 800 miles from the nearest existing grizzly bear population. The San Juan Mountains are remote and it is possible that a few remnant bears could exist for many years and escape detection, but the likelihood of a remaining population of bears is very low.

In 1975 the grizzly was declared a threatened species in the lower 48 United States and came under the protection of the Endangered Species Act. This listing brought attention to the habitat and population management needs of this species. Research was initiated in areas outside National Parks, actions that could impact habitat such as timber harvest and road building were modified to minimize
impacts on grizzly bears. Sanitation was improved in both front country areas around towns and campgrounds, as well as back country areas in wilderness and National Parks. The long-standing National Park Service policy of feeding garbage to bears was eliminated in both Glacier and Yellowstone National Parks.

The current distribution of the grizzly bear in the states of Wyoming, Montana, Idaho and Washington is shown in Figure 5.4.