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105 



rules of thumb for population viability. Clearly, 

 the small populations of the North Cascade. 

 Selkirk, and Bittenoot ecosystems, the San 

 Juan Mountains, and the U.S. portion of the 

 Cabinet- Yaak ecosystem are not viable. 

 Although the North Cascade ecosystem is close 

 to 26.000 km- (10,000 mi-), its prospects are 

 compromised by its isolation, even from popu- 

 lations in Canada. Similarly, although the 

 Cabinet- Yaak and Selkirk populations can 

 potentially receive bears that have dispersed 

 from other populations, their 5,200-km- (2.000- 

 mi-) ranges are within the size boundaries of 

 many U.S. populations that went extinct 

 between 1920 and 1970 (Fig. 2) and are similar 

 to those of European populations that appear to 

 be declining toward extinction. 



Prospects for the larger Northern 

 Continental Divide and Greater Yellowstone 

 populations are better but still uncertain. The 

 Yellowstone population is probably no larger 

 than 420 animals (Table) and is very isolated, 

 making its long-term status tenuous. The 

 Northern Continental Divide population proba- 

 bly has the best prospects because it is the 

 largest population, in the largest area, and with- 

 in the range of movement of other grizzly bear 

 populations. Nonetheless, even this population 

 is near the thresholds of 450 animals and the 

 26,000-km- (10,000-mi-) range size historical- 

 ly associated with persistence of grizzlies in the 

 United States and Europe. 



The prognosis for the Selkirk. Cabinet-Yaak. 

 and Northern Continental Divide populations 

 might be improved if their connections with 

 Canadian grizzly populations were considered. 

 These southern Canadian grizzlies, however, do 

 not have protection comparable to the U.S. 

 Endangered Species Act and. outside of national 

 parks, they are all hunted. There is also serious 

 debate over the status of Canadian grizzly popu- 

 lations, especially in southwest Alberta and the 

 northern Selkirks. Thus, there is no evidence that 

 Canadian grizzlies will guarantee the long-temi 

 survival of neighboring U.S. populations. 



Implications 



Since listing of the species under the 

 Endangered Species Act in 1975, populations 

 have probably stabilized in the Yellowstone and 

 Northern Continental Divide ecosystems. Little if 

 any of the former range has been reoccupied. 

 however, and five of seven potential or existing 

 populations do not have optimistic prospects, and 

 even the two largest populations remain at risk. 



About 88% of all grizzly bears that have 

 been studied and died within the United States 

 during the last 20 years were killed by humans, 

 both legally and illegally. Humans remain the 

 almost exclusive source of grizzly mortality. 



despite protection under the Endangered 

 Species Act. Improved protection of these pop- 

 ulations is accordingly dependent upon reduc- 

 ing the frequency of contact between grizzly 

 bears and humans, primarily by managing lev- 

 els of human activity in areas where we want 

 grizzly bears to survive. 



The Selkirk and Cabinet-Yaak grizzly bear 

 populations may also need to be augmented by 

 management if they are to survive beyond the 

 next 100 years, whereas the North Cascade, 

 Bitterroot, and San Juan populations will 

 require the import of bears from elsewhere if 

 they are to grow or persist even in the short 

 term. The Yellowstone and Northern 

 Continental Divide populations will need at 

 least existing levels of protection, along with 

 reliable monitoring and timely management. 



References 



Allendort', F.W., R.B. Harris, and L.H. Metzgar. 1991. 

 Estimation of effective population size of grizzly bears 

 by computer simulation. Pages 650-654 in E.C. Dudley, 

 ed. Ttie unity of evolutionary biology: Proceedings of the 

 Fourth International Congress of Systematic and 

 Evolutionary Biology. Vol. 2. Dioscorides Press. 

 Portland. OR. 



Almack. J.A.. W.L. Gaines, PH. Morrison. J.R. Eby. R.H. 

 Naney. G.F. Woolen. S.H. Fitkin. and E.R. Garcia. 1991. 

 North Cascades grizzly bear ecosystem evaluation: final 

 report. Interagency Grizzly Bear Committee. Denver. 

 CO. 146 pp. 



Aune. K.. and W. Kasworm. 1989. Final report: East Front 

 grizzly studies. Montana Department of Fish. Wildlife, 

 and Parks. Helena. 332 pp. 



Blanchard. B.M.. and R.R. Knight. 1991. Movements of 

 Yellowstone grizzly bears. Biological Conservation 

 58:41-67. 



Keating. K.A. 1986. Historical grizzly bear trends in 

 Glacier National Park. Montana. Wildlife Society Bull. 

 14:83-87. 



Kmght. R.. J. Beecham. B. Blanchard. L. Eberhardt. L. 

 Metzgar. C. Servheen. and J.Talbott. 1988. Report of the 

 Yellowstone grizzly bear population task force: equiva- 

 lent population size for 45 adult females. Interagency 

 Grizzly Bear Committee. Denver CO. 8 pp. 



Knight. R.R., B.M. Blanchard, and D.J. Mattson. 1993. 

 Yellowstone grizzly bear investigations: annual report of 

 the Interagency Study Team 1992. National Park Service. 

 Bozeman. MT. 26 pp. 



Mattson. D.J., and M.W. Reid. 1991. Conservation of the 

 Yellowstone grizzly bear. Conservation Biology 5:364- 

 372. 



McLellan. B.N. 1989. Dynamics of a grizzly bear popula- 

 tion during a period of industrial resource extraction. 3. 

 Natality and rate of increase. Canadian Journal of 

 Zoology 67:1865-1868. 



Merriam. C.H. 1922. Distribution of grizzly bears in U.S. 

 Outdoor Life (December):405-406. 



MFWP. 1993. Five year update of the programmatic envi- 

 ronmental impact statement: the grizzly bear in north- 

 western Montana. 1986-1990. Montana Department of 

 Fish. Wildlife, and Parks, Helena. 228 pp. 



USFWS. 1993. Gnzzly bear recovery plan. U.S. Fish and 

 Wildlife Service. Missoula, MT. 181 pp. 



Wielgus. R.B. 1993. Causes and consequences of sexual 

 habitat segregation in grizzly bears. Ph.D. thesis. 

 University of British Columbia. Vancouver 88 pp. 



For further information: 



David J. Mattson 



National Biological Service 



Cooperative Park Studies Unit 



Department of Fish and Wildlife 



Resources 



University of Idaho 



Moscow. ID 83843 



