BRC-BIO: Indirect responses of rodents to overabundant herbivores

About This Grant

Interactions between species are fundamentally important to life on Earth. Direct interactions between species, like predation, herbivory, or parasitism, play a key role in shaping ecosystems. Measuring the strength of these species interactions is an important goal of ecology. However, species can also interact indirectly, such as when one organism modifies another organism’s habitat, causing a change in behavior. These indirect interactions are often equally important as classic direct interactions, but are much more difficult to measure. Developing better tools to quantify such indirect interactions will help forecast species interactions, and therefore manage land more efficiently. This project will investigate how a common large herbivore (white-tailed deer) indirectly shapes the number and behavior of rodents in northeastern US forests by changing rodent habitats. The project will provide training opportunities for several undergraduate, community college, and graduate students, including a professional development workshop to network with biologists working across a range of academic and non-academic careers. New knowledge from this study will also be shared with state conservation agencies to help landowners manage forests. This project will test three hypotheses about interactions between deer and rodents in northeastern US forests by building a series of deer, predator, and rodent exclosure fences. First, it will test how deer indirectly shape rodent communities and ecosystem functions. Because deer over-browsing simplifies habitat structure, the researchers expect that rodent communities in unfenced controls will be dominated by a few generalist species. The researchers predict that where deer are present, rodents will have a narrower dietary niche due to competition for food, and higher prevalence of Lyme disease given that ticks can transmit pathogens between rodents and deer. Second, the project will examine how deer modify relationships between rodents and their predators. As deer browsing can reduce the shrub layer, an important predation refuge for rodents, the researchers expect that rodents will be warier of predators and reduce activity in forests with overabundant deer. Finally, the project will examine how rodents and deer influence plant biodiversity, both alone and in combination, by tracking tree growth from seed inside and outside our exclosures. The researchers predict that when deer are absent, rodents will play a greater role in suppressing plant growth, changing both the number and type of plants consumed. Altogether, this experiment will improve ecologists’ understanding about how animals drive forest regeneration, providing a stronger insight into how food webs operate and improving principles of forest management. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.