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The demographic basis of population regulation in Columbian ground squirrels

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dc.contributorStephen Dobson,
dc.creatorDobson, Stephen
dc.creatorOli, Madan
dc.description.abstractEnvironmental factors influence the dynamics and regulation of biological populations through their influences on demographic variables, but demographic mechanisms of population regulation have received little attention. We investigated the demographic basis of regulation of Columbian ground squirrel (Spermophilus columbianus) populations under natural and experimentally food-supplemented conditions. Food supplementation caused substantial increases in population density, and population densities returned to pretreatment levels when the supplementation ended. Control (untreated) populations remained relatively stable throughout the study period (1981-1986). Because food resources regulated the size of the ground squirrel populations, we used life-table response experiment (LTRE) analyses to examine the demographic basis of changes in population growth rate and thus also demographic influences on population regulation. LTRE analyses of two food-manipulated populations revealed that changes in age at maturity and fertility rate of females generally made the largest contributions to observed changes in population growth rate. Thus, our results suggested that abundance of food resources regulated the size of our study populations through the effects of food resources on age at maturity and fertility rates. Our results also indicated that different demographic mechanisms can underlie population regulation under different environmental conditions, because lower juvenile survival substantially contributed to population decline, but in only one of the populations. Demographic analyses of experimental data, such as those presented here, offer a rigorous and unambiguous means to elucidate the demographic basis of population regulation and to help identify environmental factors that underlie dynamics and regulation of biological populations.en_US
dc.publisherUniversity of Chicago Pressen_US
dc.relation.ispartofAMERICAN NATURALISTen_US
dc.rights©The Authors 2001. ©University of Chicago Press 2001. This is this the version of record published by the University of Chicago Press. It is made available under the CC-BY-NC-ND 4.0 license. Item should be cited as: Dobson, F. Stephen, and Madan K. Oli. "The demographic basis of population regulation in Columbian ground squirrels." The American Naturalist 158, no. 3 (2001): 236-247.en_US
dc.subjectdemographic mechanismsen_US
dc.subjectelasticity analysisen_US
dc.subjectlife-table re-sponse experiment (LTRE) analysisen_US
dc.subjectpartial life cycle modelen_US
dc.subjectpopulation regulationen_US
dc.subjectSpermophilus columbianusen_US
dc.titleThe demographic basis of population regulation in Columbian ground squirrelsen_US
dc.type.genreJournal Article, Academic Journalen_US

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