Food Web Ecology: Cascading Effects of Top Predators

balckfoot enclosure

At the simplest level, food webs describe who eats who in a community. However, beyond this description, food webs can summarize the important ecological interactions that influence the population growth and abundance of species in a community. We are interested in how top predators, through their effects on consumers, influence plant abundance, productivity and comunity organization.

In collaboration with Dr. Dean Pearson (U.S. Forest Service), we are currently conducting a long-term and large-scale manipulative experiment to determine how mid-sized mammalian carnivores (weasel, fox, coyote, badger, mountain lion, etc.) and raptors, as a group, influence herbivorous and granivorous small mammal behavior, abundance and population dynamics, and how small mammals in-turn affect plant abundance, community assembly, grassland productivity and diversity. Our goal is to quantify the strength of direct effects of predators on their prey and consumers on vegetation, and in doing so determine the strength of indirect whether predators have cascading indirect effects on terrestrial plant communities.

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Our research, now in its eleventh year, takes place in spectacular native grasslands in the Blackfoot Valley of western Montana. This is one of the few locations in North America where the entire predator assemblage remains intact. Starting over a decade ago, we established replicate 1 hectare plots where we either exclude: 1) all predators and native grazers, 2) native grazers (deer and elk) only, and 3) none of these animals. Within these large plots we embedded smaller 10 m x 10 m rodent exclosures to examine rodent impacts on vegetation. We continue to monitor various components of the food web to understand how predator and/or ungulate removal influences an assemblage of small mammal consumers and in-turn determine how small mammals influence plant abuandance and plant community dynamics. Relevant publications: (Maron et al. 2010, Maron and Pearson 2011).

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