Dispersal, Individuality, and Lifetime Reproductive Success

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Population dynamics is considered to be the demographic summation of individual attempts to maximize evolutionary fitness, measured as lifetime reproductive success (LRS). Many offspring disperse; therefore, reproductive success of parents cannot be determined without knowing the survivorship and reproductive output of their dispersing offspring. An animal should not disperse unless dispersal increases its fitness; therefore, dispersal must be considered from the fitness viewpoint of dispensers. The contributions of dispersal, social behavior, individual differences, and social organization to fitness can be determined from detailed, longitudinal, long-term studies of individuals whose life-history traits of relatedness, age, and sex are known, whose behavioral phenotype can be categorized, and whose social interactions can be directly observed. This project will be the first to incorporate the reproductive success of offspring into the calculations of the variance in lifetime reproductive success of individual males and females. The energetic costs of male mating strategies will be compared with the reproductive costs of females to determine which sex, if either, has the greatest costs during the active season. Many rodent populations require control. When population control should be applied to be cost effective can be determined from the population biology of the species. Thus, if most animals that disperse die, then it is not effective to apply control measures to animals that would die anyway. Also, control measures are ineffective if those animals that are killed or removed are quickly replaced by immigrants. Because yellow-bellied marmots frequently are agricultural pests, knowledge of the fate of dispensers will contribute to the preparation of effective control measures.