Document Type


Journal/Book Title/Conference

Ecological Applications






Ecological Society of America

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Food web theory predicts that the loss of large carnivores may contribute toelevated predation rates and, hence, declining prey populations, through the process ofmesopredator release. However, opportunities to test predictions of the mesopredator releasehypothesis are rare, and the extent to which changes in predation rates influence preypopulation dynamics may not be clear due to a lack of demographic information on the preypopulation of interest. We utilized spatial and seasonal heterogeneity in wolf distribution andabundance to evaluate whether mesopredator release of coyotes (Canis latrans), resulting fromthe extirpation of wolves (Canis lupus) throughout much of the United States, contributes tohigh rates of neonatal mortality in ungulates. To test this hypothesis, we contrasted causes ofmortality and survival rates of pronghorn (Antilocapra americana) neonates captured at wolf-free and wolf-abundant sites in western Wyoming, USA, between 2002 and 2004. We thenused these data to parameterize stochastic population models to heuristically assess the impactof wolves on pronghorn population dynamics due to changes in neonatal survival. Coyotepredation was the primary cause of mortality at all sites, but mortality due to coyotes was 34%lower in areas utilized by wolves (P , 0.001). Based on simulation modeling, the realizedpopulation growth rate was 0.92 based on fawn survival in the absence of wolves, and 1.06 atsites utilized by wolves. Thus, wolf restoration is predicted to shift the trajectory of thepronghorn population from a declining to an increasing trend. Our results suggest thatreintroductions of large carnivores may influence biodiversity through effects on preypopulations mediated by mesopredator suppression. In addition, our approach, whichcombines empirical data on the population of interest with information from other datasources, demonstrates the utility of using simulation modeling to more fully evaluateecological theories by moving beyond estimating changes in vital rates to analyses ofpopulation-level impacts.