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Grizzly Bear and Black Bear Ecology

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SYNOPSIS

grizzly bear paw print in snowPower of Sign Surveys to Detect Bear Population Trends: The grizzly bears in Glacier National Park represent the keystone of the Northern Continental Divide Ecosystem population in NW Montana. Because of its proximity to Canadian bear populations, large land area, and high proportion of designated wilderness and national park lands, the Northern Continental Divide Ecosystem has the best long-term prospects of supporting a viable grizzly bear population among the six areas designated as grizzly bear recovery zones in the United States. Yet there never has been a demographic study of the Glacier National Park grizzly bear population and no data exist on population size, status, or trend. The grizzly bear population in the Northern Continental Divide Ecosystem can not be  delisted without reliable information on ecosystem-wide population trends, of which the bears in Glacier National Park are a critical component. Until now, statistically rigorous grizzly population studies in forested habitat could only be accomplished with radio telemetry.

Traditional studies entail intensive trapping with baiting, drugging, collaring, ear tagging, and frequent aerial radio tracking. Large numbers of grizzly bears are handled. Trapping requires closure of portions of the park to visitors. The presence of collared/marked bears and frequent   overflights impinge on visitor wilderness and solitude experiences. Not only do these techniques disturb bears, but they are expensive to conduct and involve long-term (5-10+ years) commitments. Cost considerations, along with ethical and social concerns, prohibit their application to most grizzly bear populations.

tree with ripped bark from bearWhile recognizing that effective bear management in national parks requires (1)maintenance of a viable population size and (2) a means of detecting significant population declines, Glacier National Park managers are sensitive to wilderness values and bear disturbance issues and would prefer a less expensive and intrusive method to monitor its bear populations than a traditional radio telemetry study. A pilot survey in Glacier National Park demonstrated the feasibility of collecting adequate sample sizes of bear sign to obtain minimum counts and to reveal population declines without handling bears or conducting aerial overflights. Since 1984, bear sign has been collected each fall from 240 km of Glacier National Park trails. Approximately 200 hair and 100 scat samples were found per year. Based on within and between year variation in the amount of sign found, simulation modeling demonstrated that a biologically significant decline in sign could be detected with this survey design if bear species could be identified from scats. Species identification is necessary because Glacier National Park is home to both grizzly and black bears with overlapping ranges. This work was published in Ecological Applications(1.27 MB)

Using DNA to Monitor Grizzly Bear Population Trends:

Recent advances in genetic technology allow identification of species, sex, and individuals from DNA extracted from bear hair and scats without handling bears. With proper survey design, identification of individuals and sex typing data can be used to determine (1) minimum population size, (2)population trends for both species, and (3) genetic diversity of the populations. Now that individual bears can be identified from hair and scats, sign surveys to monitor population trend will be more powerful than demonstrated by Kendall et al. (1992).

In a study that began in 1998, DNA is being analyzed from bear sign collected along survey routes in Glacier National Park and adjoining lands. The fundamental goal of this work is to develop a  nonintrusive, relatively inexpensive method to monitor grizzly bear population status and trend in the Northern Continental Divide Ecosystem. The number of individuals and species identified will be used to develop minimum counts and baseline population indices. The power of surveys with varying sample designs will be compared using methods described by Kendall et al. (1992).

Grizzly bear conservation biology: An assessment of the status of grizzly bear populations in the contiguous United States offers a new approach to population viability analysis which has implications for grizzly bear conservation strategy (Mattson et al. 1995). A study, begun in 1998, that will use DNA extracted from sign to monitor bear population trends, will also address bear conservation genetics as described above.

Bear behavior and management in Glacier National Park: Gniadek and Kendall (1997) use comprehensive records of grizzly and black bear activity in Glacier National Park to evaluate the efficacy of the park’s bear management program. The rate of grizzly bear/human confrontation in Glacier National Park appears to have risen in the past several decades but the rate is based on the number of visitors driving into the park. Recognizing that meaningful rates must be calculated with the number of hikers and that the park had no estimate of backcountry trail use, a trail use study was conducted 1988-1990. Trail use throughout the park was estimated and a predictive model of backcountry day use was developed (McCool et al. 1989, 1990; Braithwaite et al.1991). The data are temporally and spatially explicit and the methodology developed for this project has become the standard for future day use monitoring in Glacier National Park.

Grizzly Bear and Black Bear Feeding Ecology: Food habits of the grizzly and black bears of Glacier National Park were summarized by  Martinka and Kendall (1986). The average annual and seasonal diet volumes of major food groups are depicted below.

Annual Food Habits of Bears:Proportionate contribution of major food classes to the total annual diet volume of bears in Glacier National Park as determined by fecal analysis, 1967-71 and 1982-85 (n=1514)

Pie chart of major food classes for Glacier NP bears

Seasonal food habits: Proportionate contribution of major food classes to seasonal diet volume of bears in Glacier National Park 1982-88.

Bears and Whitebark Pine: In healthy whitebark pine ecosystems, whitebark pine seeds are a rich and highly preferred source of food for a variety of birds and mammals including grizzly and black bears. Much of whitebark pine cone crops are harvested by red squirrels who cut the cones down and bury them in mounds of forest litter called  middens. Because whitebark pine cones do not fall off the tree or drop their seeds the year they ripen, and grizzly bears can not climb trees, grizzlies must rob squirrel middens to feed on whitebark pine seeds. The importance of  whitebark pine seeds or "nuts" to the diet of grizzly bears in Yellowstone National Park, and to wildlife in general, is described in Kendall (1983) and Kendall and Arno (1990). Following bumper whitebark cone crop years, pine nuts can dominate the food habits of bears for the entire next year. Bears can even locate cones under 6 feet of snow.

mountainEcology and bear use of alpine moth aggregations: Bear food habits research documented that bears in the Greater Glacier Ecosystem  (GGE) feed on army cutworm moths. From entomological studies, it was known that these moths migrate in early summer from the Great Plains to spend the summer in the Rocky Mountains. In Glacier NP, army cutworm moths spend their days resting in the cool spaces between jumbled rocks in talus fields near the tops of some of Glacier's highest peaks. The moths emerge at night to feed on nearby flower nectar. Research on bear use of moths in the GGE and the alpine ecology of army cutworm moths estimated the nutritional importance of this diet item; during peak feeding periods when moths are abundant, bears eat approx. 40,000 moths/day which is equivalent to 20,000 kcal/day. army cutworm mothThis study also addressed moth densities in talus fields where bears feed, physical parameters of known moth aggregation sites, locations of potential moth sites modeled on a GIS, body composition and migration potential of moths and the energetic cost of climber disturbance of bears feeding on moths. This work is reported in White et al. (1998)(1998)and (1999). 

Bears and Berries:

huckleberriesFactors influencing wild fruit production: Wild berries, especially huckleberries, are key bear foods in the Greater Glacier Ecosystem (GGE). Research on wild fruit production, reported in Kendall (1986) and Weaver et al. (1990), examined annual production trends of several species of fruiting shrubs and found that huckleberry crops were regionally synchronous. Large-scale climatic patterns probably account for gross fluctuations in annual production.

Constraints to frugivory by bears: Other research builds on knowledge of bear behavior when feeding on berries and fluctuations in bear food habits and in production of wild berries. Feeding trials of captive and wild bears measured intake rate, physiological capacity, and metabolic efficiency to elucidate energetic constraints involved with bear  frugivory. This research, which is reported in Welch et al. (1997), contributes to understanding of bear foraging strategy and efficiencies and the importance of berry clustering and bush configuration (i.e. leaf to berry ratios) to growth rates of wild bears.

CONTACT

Katherine Kendall kkendall@usgs.gov 406-888-7994
USGS-BRD
Science Center, c/o Glacier National Park
West Glacier, Montana 59936-0128

PRINCIPAL INVESTIGATOR

Katherine Kendall

RELATED PUBLICATIONS

  • White, Don, Jr., Katherine C. Kendall, and Harold D. Picton. 1999. Potential energetic effects of mountain climbers on foraging grizzly bears. Wildlife Society Bulletin 27:(1)146-151.
  • White, Don, Jr., Katherine C. Kendall, and Harold D. Picton. 1998. Seasonal occurrence, body composition, and migration potential of army cutworm moths in northwest Montana. Canadian Journal of Zoology 76:835-842.
  • White, Don, Jr., Katherine C. Kendall, and Harold D. Picton.1998. Grizzly bear feeding activity at alpine army cutworm moth aggregation sites in northwest Montana. Canadian Journal of Zoology 76:(2)221-227.
  • Kendall, K.C. and D. Schirokauer. 1997. Alien threats and restoration dilemmas in whitebark and limber pine communities. Proceedings of the George Wright Society Conference on Research and Resource Management in Parks and on Public Lands. 9:218-225.
  • Welch, C.A, J. Keay, K.C. Kendall, and C.T. Robbins. 1997. Constraints to frugivory by bears. Ecology 78(4):1105-1119.
  • Gniadek, S.J. and K.C. Kendall. 1997. A summary of bear management in Glacier National Park, Montana, 1960-1994. Int. Conf. Bear Res. Manage. Ursus10:155-159.
  • Kendall, K.C. 1997. Limber pine. In: Mac, M.J., P.A. Opler, C.E. Haecker-Puckett, P.D. Doran and L.S. Huckaby editors. Status and trends of the nation's biological resources. 2 Vols.US Department of the Interior. Washington, DC. pg.486. 994 pp.
  • Kendall, K.C. 1997. Whitebark pine. In: Mac, M.J., P.A. Opler, C.E. Haecker-Puckett, P.D. Doran and L.S. Huckaby editors. Status and trends of the nation's biological resources. 2 Vols.US Department of the Interior. Washington, DC. pg.483-485. 994 pp.
  • Kendall, K.C. 1996. Whitebark pine ecosystems: Status and trends. Proceedings of the Annual Alberta-British Columbia Intermountain Forest Health Workshop. 4:88-98. Parks Canada, Radium Hot Springs, BC.
  • Kendall, K., D. Schirokauer, E. Shanahan, R. Watt, D. Reinhart, R. Renkin, S. Cain and G. Green. 1996a. Whitebark pine health in northern Rockies national park ecosystems: A preliminary report. Nutcracker Notes 7:16. USDA Forest Service, Intermountain Research Station, IFSL, Missoula, MT.
  • Kendall, K., D. Tyers, and D. Schirokauer. 1996b. Preliminary status report on whitebark pine in Gallatin National Forest, Montana. Nutcracker Notes 7:19. USDA Forest Service, Intermountain Research Station, IFSL, Missoula, MT.
  • Kendall, K., D. Ayers, and D. Schirokauer. 1996c. Limber pine status from Alberta to Wyoming. Nutcracker Notes 7:23-24. USDA Forest Service, Intermountain Research Station, IFSL, Missoula, MT.
  • Mattson, D.J., R.G. Wright, K.C. Kendall, and C.J. Martinka. 1995. Status and trends of grizzly bear populations in the contiguous United States. Pages 103-105 in E.T. LaRoe, G.S. Farris, C.E. Puckett, P.D. Doran, and M.J. Mac, editors. Our living resources: A report to the nation on the distribution, abundance, and health of US plants, animals, and ecosystems. USDI, National Biological Service, Washington, DC.
  • Kendall, K.C. 1995. Whitebark pine: Ecosystem in peril. Pages 228-230 in E.T. LaRoe, G.S. Farris, C.E. Puckett, P.D. Doran, and M.J. Mac, editors. Our living resources: A report to the nation on the distribution, abundance, and health of US plants, animals, and ecosystems. USDI, National Biological Service, Washington, DC.
  • Kendall, K.C. and R.J. Hoff. 1995. An introduction to whitebark pine ecology and status. Proceedings of the Annual Western International Forest Disease Work Conference. 43:97-102.
  • Kendall, K.C. 1994. A case for monitoring whitebark pine stands. Nutcracker Notes 4:2. USDA Forest Service, Intermountain Research Station, IFSL, Missoula, MT.
  • Kendall, K.C. 1994. Whitebark pine conservation in North American national parks. Pages 302-307 in W. Schmidt and F.K. Holtmeier, eds. Proceedings-International workshop on subalpine stone pines and their environment: The status of our knowledge. USDA Forest Service, Intermountain Research Station, Ogden, UT. General Technical Report INT-GTR-309.
  • Picton, H. and K.C. Kendall. 1992. Chromatographic differentiation of grizzly and black bear scats. Int. Conf. Bear Res. Manage. 9:497-501.
  • Kendall, K.C., L.H. Metzgar, D.A. Patterson, and B.M. Steele. 1992. Power of sign surveys to monitor population trend. Ecological Applications 2(4):422-430.
  • Braithwaite, A.M., S.J. McCool, and K.C. Kendall. 1991. Backcountry day use in the Many Glacier Valley, Glacier National Park. Final Rep. for the 1988-90 project. USDI National Park Serv., Glacier National Park, and The Institute for Tourism and Recreation, University of Montana, Missoula. 18 pp.
  • Weaver, T., K. Kendall, and F. Forcella. 1990. Berry production in three whitebark pine forest types. Proc. Whitebark Pine Symposium. USDA Forest Service General Tech. Rep. INT-270. Pg. 198-200.
  • Kendall, K.C. and S.A. Arno. 1990. Whitebark pine -- An important but endangered wildlife resource. Proc. Whitebark Pine Symposium. USDA Forest Service General Tech. Rep. INT-270. Pg. 264-273.
  • McCool, S.J., A.M. Braithwaite, A. Walker, and K.C. Kendall. 1990. Backcountry day use in the Many Glacier Valley, Glacier National Park. Final Rep. for the 1989 season. USDI National Park Serv., Glacier National Park, and The Institute for Tourism and Recreation, University of Montana, Missoula. 19 pp.
  • McCool, S.J., A.M. Braithwaite, and K.C. Kendall. 1989. An estimate of backcountry day use of Glacier National Park. Final Rep. for the 1988 season. USDI National Park Serv., Glacier National Park, and The Institute for Tourism and Recreation, University of Montana, Missoula. 53 pp.
  • Kendall, K.C. 1986. Grizzly and black bear feeding ecology in Glacier National Park, Montana. Prog. Rep. 1982-1985. USDI National Park Serv., Glacier National Park, Montana. 42 pp.
  • Martinka, C.J. and K.C. Kendall. 1986. Grizzly bear habitat research in Glacier National Park, Montana. Pg. 19-23 in Proc. Grizzly Bear Habitat Symposium, USDA Forest Service General Tech. Rep. INT-207
  • Kendall, K.C. 1983. Use of pine nuts by grizzly and black bears in the Yellowstone area. Int. Conf. Bear Res. Manage. 5:166-173.
KEYWORDS
black bear ecology; grizzly bear ecology; huckleberry production trends; Pinus albicaulis; population trends; Ursus americanus; Ursus horribilis; Vaccinium globulare; whitebark pine communities
GEOGRAPHIC DISTRIBUTION
Glacier National Park; Grand Teton National Park; Montana; Wyoming; Yellowstone National Park

   For More Publications see: 

Content Information Contact: kkendall@usgs.gov