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THE RELATIVE CONTRIBUTIONS OF DEMOGRAPHIC COMPONENTS TO POPULATION GROWTH: A DIRECT ESTIMATION APPROACH BASED ON REVERSE-TIME CAPTURE-RECAPTURE

Abstract. We consider methods for estimating the relative contributions of different demographic components, and their associated vital rates, to population growth. We identify components of the population at time i (including a component for animals not in the population at i) and for each such component ask the question: "What is the probability that an individual randomly selected from the population at time i+1 was a member of this component at i?" The estimation methods for these probabilities (gamma_i) are based on capture-recapture studies of marked animal populations and use reverse-time modeling (Pollock et al. 1974, Nichols et al. 1986, Pradel 1996). We consider several different sampling situations and present example analyses for meadow voles, Microtus pennsylvanicus. The relationship between these gamma_i parameters and elasticities (and other parameters based on projection matrix asymptotics) is noted and discussed. We conclude by suggesting that model-based asymptotics be viewed as demographic theory and that direct estimation approaches such as those presented here and by Pradel (1996) be used to test this theory with data from sampled populations with marked animals.

Key words: animal population ecology, capture-recapture models, contributions of demographic components, elasticity, meadow voles, Microtus pennsylvanicus, population growth rate, population projection matrix

Key phrases: asymptotic theory of population growth, contributions of demographic components to population growth rate, reverse-time capture-recapture models

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