TY - JOUR
T1 - Estimating effects of adult male mortality on grizzly bear population growth and persistence using matrix models
AU - Wielgus, Robert B.
AU - Sarrazin, Francois
AU - Ferriere, Regis
AU - Clobert, Jean
N1 - Funding Information:
Funding was provided by the Alberta Fish and Wildlife Branch; Alberta Recreation, Parks, and Wildlife Foundation; B.C. Ministry of Environment; B.C. Ministry of Forests; B.C. Ministry of Parks; Boreal Institute; Carthy Foundation; CNRS Lab D'Ecologie; Crestbrook Forest Industries; Darkwoods Forestry; Ecole Normale Superieure; Forest Renewal B.C.; James Robert Thompson Foundation; Home Oil Ltd.; Idaho Department of Fish and Game; Natural Sciences and Engineering Research Council of Canada; Science Council of B.C.; Trail Wildlife Assoc.; University of British Columbia; Universite Pierre et Marie Curie; U.S. Fish and Wildlife Service; U.S. Forest Service; Washington Department of Fish and Wildlife; Washington State University; and World Wildlife Fund (Canada). Fieldwork and technical assistance were provided by J. Almack, J. Bicknell, K. Chambers, B. Compton, R. Dice, H. Carr, R. Foreman, D. Johnson, S. Knick, C. Mamo, T. Manning, L. Meszaros, B. Pelchat, G. Servheen, R. Steiner, M. Super, W. Wakkinen, and P. Zager. The late O. Pall helped train Wielgus in aerial telemetry and conducted many telemetry flights prior to Wielgus's participation. We lost him during one of his flights in Kananaskis and remember him fondly. The manuscript benefited from the comments and discussion of E. Danchin, D. Mattson, J. Weaver, G. Wright, and anonymous reviewers.
PY - 2001
Y1 - 2001
N2 - We radio monitored a hunted, sexually segregated grizzly bear (Ursus arctos) population and an unhunted, unsegregated population for demographics and constructed a stage- and age-classified matrix model to test for the effects of adult male mortality and resulting sexual segregation on population growth and persistence. Population parameters in the model were adult female survival, subadult female survival, offspring survival, probability of litter sizes, and probability of unsuccessful pregnancy. The last three parameters were affected by adult male mortality and segregation, the others were not. We compared population growth with and without effects of hunting by holding adult female and subadult female survival constant and by using hunted and unhunted values for offspring survival, litter size, and pregnancy. Population growth (Lambda) showed the greatest elasticity for adult survival, subadult survival, offspring survival, litter size, and unsuccessful pregnancy, in that order. This corresponds with observed anti-infanticide tactics (sexual segregation) by adult females to maximize their fitness. The hunted population decreased at a rate of 0.99 whereas the simulated, unhunted population increased at a rate of 1.05. The hunted population was much more susceptible to population extinction. Under demographic stochasticity mean time to extinction was 32 years in the hunted population and 110 years in the unhunted population. Under environmental stochasicity mean time to extinction was 21 years in the hunted population and 43 years in the unhunted population. We suggest that sexual segregation caused by hunting resident adult males can result in population decline and can even contribute to rapid population extinctions when numbers are small.
AB - We radio monitored a hunted, sexually segregated grizzly bear (Ursus arctos) population and an unhunted, unsegregated population for demographics and constructed a stage- and age-classified matrix model to test for the effects of adult male mortality and resulting sexual segregation on population growth and persistence. Population parameters in the model were adult female survival, subadult female survival, offspring survival, probability of litter sizes, and probability of unsuccessful pregnancy. The last three parameters were affected by adult male mortality and segregation, the others were not. We compared population growth with and without effects of hunting by holding adult female and subadult female survival constant and by using hunted and unhunted values for offspring survival, litter size, and pregnancy. Population growth (Lambda) showed the greatest elasticity for adult survival, subadult survival, offspring survival, litter size, and unsuccessful pregnancy, in that order. This corresponds with observed anti-infanticide tactics (sexual segregation) by adult females to maximize their fitness. The hunted population decreased at a rate of 0.99 whereas the simulated, unhunted population increased at a rate of 1.05. The hunted population was much more susceptible to population extinction. Under demographic stochasticity mean time to extinction was 32 years in the hunted population and 110 years in the unhunted population. Under environmental stochasicity mean time to extinction was 21 years in the hunted population and 43 years in the unhunted population. We suggest that sexual segregation caused by hunting resident adult males can result in population decline and can even contribute to rapid population extinctions when numbers are small.
KW - Adult
KW - Grizzly bears
KW - Mortality
KW - Offspring
KW - Population growth
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U2 - 10.1016/S0006-3207(00)00168-3
DO - 10.1016/S0006-3207(00)00168-3
M3 - Article
AN - SCOPUS:0035081455
SN - 0006-3207
VL - 98
SP - 293
EP - 303
JO - Biological Conservation
JF - Biological Conservation
IS - 3
ER -