. The Canadian field-naturalist. Natural history. 230 The C.\n.\dlan Field-Natl'r.\list Vol. 109 years, up to three surveys were carried out in October and/or November. Corrected independent population estimates were made for the Mont .AJben and Mont Jacques-Canier groups, using the proportion of radio-tagged females observed during composition counts to estimate the proportion of all females seen. Variance of correc- tion factors was estimated with the binomial distrib- ution. As contact was lost with some radio-tagged animals, it was impossible to determine if such radio-collars \\ere broken
. The Canadian field-naturalist. Natural history. 230 The C.\n.\dlan Field-Natl'r.\list Vol. 109 years, up to three surveys were carried out in October and/or November. Corrected independent population estimates were made for the Mont .AJben and Mont Jacques-Canier groups, using the proportion of radio-tagged females observed during composition counts to estimate the proportion of all females seen. Variance of correc- tion factors was estimated with the binomial distrib- ution. As contact was lost with some radio-tagged animals, it was impossible to determine if such radio-collars \\ere broken but still observable on U\- ing Caribou during censuses, or if they were remo\ed from the study area, and undetectable dur- ing sur\eys. We considered two scenarios: (1) radio failure but collar still present on a living animal, and (2) death of the animal and radio on the ground or removed from the study area. The first alternative produced maximum population estimates while the second yielded minimum ones. WTien two sup-eys were carried out during the same aummn. we used the more precise estimate. We estimated the demographic trend of the herd. based on productivit}' and mortalit}' rates obser\ed during the course of this study. Number of female Caribou in the population was estimated by age class from 1983 to 1992. The smoothed age structure cal- culated by Messier et al. (1988: Table 5) served as initial age distribution in 1983 because reproduction appeared relatively stable in previous years. Observed annual survival rate of radio-tagged females was used for all age classes ber\.veen 1987 and 1992. and the average for this period was uti- lized for years without telemetr\" data and for the Mont .Albert and Mont Jacques-Cartier group, respecti\ely). Survival rate was assumed to be 0 for the last age class, 15 year-olds. Recruitment was estimated from calf:cow ratios observed during autumn composition counts, after summer mortaht\^ occurred. Female pop
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