Grizzly bear

Wildlife Biology, 2005

We collected hair samples from bears and used microsatellite genotyping to identify individual bears on three study areas near the Canadian Rocky Mountains. We estimated density of grizzly bears Ursus arctos in eight different ecosystems across five study areas, including the reanalysis of two previously published data sets. We also estimated black bear U. americanus density for two ecosystems in one study area. Grizzly bear density was lowest in boreal and subboreal plateau areas, moderate in the Rocky Mountain east slopes and highest in the Rocky Mountain west slopes. Presumably these gross differences are related to ecosystem productivity. In the Rocky Mountain west slopes, grizzly bear density was lower in populations that were partially isolated from the continuous bear population to the north. Presumably, these differences have more to do with human impacts on habitat and survival than ecosystem productivity, because productivity in partially isolated areas was similar to productivity in adjacent continuous populations. We show that large differences in bear density occur down to the ecoregion scale; broader ecosystem classes such as Banci's (1991) grizzly bear zones, ecoprovinces or ecozones would include areas with major differences in density and are therefore too coarse a scale at which to predict grizzly bear density. There appears to be little movement across ecoregion boundaries further suggesting that this may be an appropriate scale at which to extrapolate density. Differences in density across finerscale ecosystems are likely due to seasonal movements and not population level differences in density. Average bear movements were longer in less productive ecosystems. Female grizzly bears did not appear to leave their home ranges to fish for salmon Oncorhynchus spp., and extra-territorial movements by males appeared to be rare, in both ecosystems which supported spawning salmon.

Bears: Their Biology and Management, 1987

An approach for relating fitness to foraging activity is described for 2 adult female grizzly bears (Ursus arctos) in coastal British Columbia. During berry season both bears roamed widely (seasonal home ranges of 3932 and 3565 ha) using at least 10 different species of berries in widely divergent habitats. Bears spent 62%-69% of their time in habitat types used for feeding. Habitat use by the bear with the smaller home range was correlated with food quantity and quality (r, = 0.79, P < 0.05); that of the more widely ranging bear was not (r, = 0.11, P > 0.1). During the berry season, both bears relied heavily on berries, but their diets differed. During the 3-year study, reproductive success of the more efficient bear (smaller home range, feeding activity correlated with food quality) was greater than that for the less efficient bear (3 vs. 2 cubs). These observations are discussed in terms of foraging theory. We conclude that 1 bear appears to be optimizing, but both bears could be satisficing.

Oecologia, 2011

Categorizing animal populations by diet can mask important intrapopulation variation, which is crucial to understanding a species' trophic niche width. To test hypotheses related to intrapopulation variation in foraging or the presence of diet specialization, we conducted stable isotope analysis (d 13 C, d 15 N) on hair and claw samples from 51 grizzly bears (Ursus arctos) collected from 2003 to 2006 in the Mackenzie Delta region of the Canadian Arctic. We examined within-population differences in the foraging patterns of males and females and the relationship between trophic position (derived from d 15 N measurements) and individual movement. The range of d 15 N values in hair and claw (2.0-11.0%) suggested a wide niche width and cluster analyses indicated the presence of three foraging groups within the population, ranging from nearcomplete herbivory to near-complete carnivory. We found no linear relationship between home range size and trophic position when the data were continuous or when grouped by foraging behavior. However, the movement rate of females increased linearly with trophic position. We used multisource dual-isotope mixing models to determine the relative contributions of seven prey sources within each foraging group for both males and females. The mean bear dietary endpoint across all foraging groups for each sex fell toward the center of the mixing polygon, which suggested relatively well-mixed diets. The primary dietary difference across foraging groups was the proportional contribution of herbaceous foods, which decreased for both males and females from 42-76 to 0-27% and 62-81 to 0-44%, respectively. Grizzlies of the Mackenzie Delta live in extremely harsh conditions and identifying within-population diet specialization has improved our understanding of varying habitat requirements within the population.

ARCTIC, 2002

We collected 169 grizzly bear scats between 1994 and 1997 to determine the dietary habits of barren-ground grizzly bears (Ursus arctos) inhabiting Canada's central Arctic. From personal observations and fecal analysis, we concluded that barrenground grizzly bears lead a predominantly carnivorous lifestyle and are effective predators of caribou (Rangifer tarandus). Caribou was a predominant diet item during spring, mid-summer, and fall. During early summer, grizzly bears foraged primarily on green vegetation. Berries increased in dietary importance in late summer. Declines in the caribou population of our study area or long-term absences of caribou may threaten the local grizzly bear population.

Bears: Their Biology and Management, 1980

The natural food habits of grizzly bears (Ursus arctos horribilis Ord) in Yellowstone National Park were investigated in 1973-74 to identify the grizzly's energy sources and trophic level(s), nutrient use, and distribution. Food consumption was determined by scat analysis and field observations. Food quality and digestibility were estimated by chemical analysis. Grizzlies were distributed in 3 distinctive feeding economies: valley/plateau, a grass/rodent economy where grizzlies were intensive diggers; mountain, primarily a grass/springbeauty/root economy where grizzlies were casual diggers; and lake, primarily a fish/grass economy where grizzlies were fishers. The economies occured in areas with fertile soils; distribution of bears within each was related to the occurrence of succulent plants. The feeding cycle in the valley/plateau and mountain economies followed plant phenology. Grizzlies fed primarily on meat before green-up and on succulent herbs afterwards; meat, corms, berries, and nuts became important during the postgrowing season. Succulent grasses and sedges with an importance value percentage of 78.5 were the most important food items consumed. Protein from animal tissue was more digestible than protein from plant tissue. Storage fats were more digestible than structural fats. Food energy and digestibility were directly related. Five principle nutrient materials (listed with their percentage digestibilities) contributed to total energy intake: protein from succulent herbs, 42.8; protein and fat from animal material, 78.1; fat and protein from pine nuts, 73.6; starch, 78.8; and sugar from berries and fruits, digestibility undetermined. Protein from succulent herbs, with a nutritive value percentage of 77.3, was the grizzlies' primary energy source. Because succulent, preflowering herbs had higher protein levels than dry, mature herbs, grizzly use of succulent herbs guaranteed them the highest source of herbaceous protein. Low protein digestibility of succulent herbs was compenstated for by high intake. Grizzlies were digestively flexible and maximized use of protein from plant and animal sources. They were adapted to the most constant and abundant sources of protein: succulent herbs and animal material from open, fertile grasslands. Competition among grizzlies for animal food during the pregrowing season may be regulatory for the grizzly population. The grizzly population level can be partially accounted for by the grizzlies' status as secondary consumers during pregreen-up periods and primary consumers during the growing and postgrowing seasons. The essential environmental requirement was the availability of fertile grasslands and herblands interspersed with cover and capable of maintaining artiodactyls, rodents, and abundant nutritious herbs as sources of food. Extensive grizzly bear (Rausch 1963) use of unnatural foods (garbage and camp groceries) in Yellowstone National Park occured from the early days of the park until closure of the Trout Creek and West Yellowstone open-pit garbage dumps in 1971 (Skinner 1925, Cole 1976). After these primary sources of unnatural foods were removed, most grizzlies resumed use of natural foods (Cole 1974). This report on grizzly bear use of natural foods is based on research conducted in 1973 and 1974 as part of the Interagency Grizzly Bear Team Study. The overall objectives were to develop hypotheses about the grizzly's natural energy sources and tropic level(s), the quality and quantity of nutrient use, and grizzly distribution. I am grateful to all those who gave help, advice, and encouragement during this study. R. R. Knight provided the research opportunity, aided in scat collection, and critically read the manuscript. H. D. Picton provided advice throughout the study and aided in preparation of the manuscript. R. J. Mackie and W. R. Gould critically read an early draft of the manuscript. J. H. Rumely aided in identification of plant specimens. G. F. Cole gave valuable advice and aided in scat collection. D. G. Despain helped to identify plant specimens, interpreted the distribution of vegetation, and aided in scat collection. D. B. Houston, M. M.

2000

We used genetic identification of individuals and mark-recapture modeling to estimate bear (Ursus) population size in both a mountainous and interior plateau environment in central eastern British Columbia. We sampled 591 sites within a 9,452-km 2 study area during June and July 2000 and detected grizzly bears (Ursus arctos) at 199 sites and black bears (U. americanus) at 316 sites. We identified 326 different grizzly bears using microsatellite profiling; there were more females than males in the sample (35M:65F). After correcting for the effects of closure bias, we estimated density to be 12 grizzly bears/1,000 km 2 (95% confidence interval [CI] 7-28) on the plateau and 49/1,000 km 2 (CI 43-59) in the mountains. These densities are considerably higher than those predicted by the habitat-based extrapolation method used for grizzly bear management in British Columbia. The incorporation of hunter harvest impacts to population size caused the greatest decline, and therefore discrepancy, in numbers between the habitat-based extrapolation and the DNA-based estimate.

Conservation Biology, 1996

The Journal of Wildlife Management, 2012

We defined patterns of habitat use and selection by female grizzly bears (Ursus arctos) in the Besa-Prophet watershed of northern British Columbia. We fitted 13 adult females with Geographic Positioning System (GPS) radio-collars and monitored them between 2001 and 2004. We examined patterns of habitat selection by grizzly bears relative to topographical attributes and 3 potential surrogates of food availability: land-cover class, vegetation biomass or quality (as measured by the Normalized Difference Vegetation Index), and selection value for prey species themselves (moose [Alces alces], elk [Cervus elaphus], woodland caribou [Rangifer tarandus], Stone's sheep [Ovis dalli stonei]). Although vegetation biomass and quality, and selection values for prey were important in seasonal selection by some individual bears, land-cover class, elevation, aspect, and vegetation diversity most influenced patterns of habitat selection across grizzly bears, which rely on availability of plant foods and encounters with ungulate prey. Grizzly bears as a group avoided conifer stands and areas of low vegetation diversity, and selected for burned land-cover classes and high vegetation diversity across seasons. They also selected mid elevations from what was available within seasonal ranges. Quantifying relative use of different attributes helped place selection patterns within the context of the landscape. Grizzly bears used higher elevations (1,595 AE 31 m SE) in spring and lower elevations (1,436 AE 27 m) in fall; the range of average elevations used among individuals was highest (500 m) during the summer. During all seasons, grizzly bears most frequented aspects with high solar gain. Use was distributed across 10 land-cover classes and depended on season. Management and conservation actions must maintain a diverse habitat matrix distributed across a large elevational gradient to ensure persistence of grizzly bears as levels of human access increase in the northern Rocky Mountains.

2005

Grizzly bear habitat in Banff National Park (BNP), Kananaskis Country (KC), and surround can be reached after a 1–2 hour drive from Calgary, an affluent city of 900,000 in Alberta, Canada. Calgary’s human population grew by 16%, 1996–2000, the fastest rate of urban growth in Canada. Nearby smaller cities and towns such as Canmore, Cochrane and Bragg Creek also had rapid growth. The oil and gas driven economy will continue to fuel rapid growth and development in Calgary and surround and will encourage more people to be in grizzly bear habitat. Grizzly bear conservation will depend upon managing the cumulative effects of humans. Grizzly bears in this area live in one of the most developed and rapidly developing landscapes where they still survive.