BRC-BIO: indirect responses of rodents to overabundant herbivores

Federal Project Grant Award Summary

Hamilton College received a $502,863 Project Grant from the National Science Foundation's Division of Biological Infrastructure under the Biological Sciences program (CFDA 47.074), effective September 1, 2025 through August 31, 2028. The award supports a three-year research project investigating indirect ecological interactions between white-tailed deer and rodent populations in Northeastern U.S. forests. The primary deliverable is empirical research quantifying how deer herbivory indirectly modifies rodent community composition, behavior, and disease prevalence through habitat alteration. The project employs experimental exclosure fencing to isolate and measure the effects of deer, predators, and rodents on ecosystem functions and will generate peer-reviewed scientific findings on species interactions applicable to forest management.

In addition to core research outputs, the grant supports substantial educational and outreach products. The project will provide research training and professional development opportunities for undergraduate, community college, and graduate students, including a professional development workshop connecting participants with biologists across academic and non-academic careers. Results and management recommendations will be disseminated to state conservation agencies and landowners to inform evidence-based forest stewardship practices. These dual research and workforce development outcomes align with the Biological Sciences program's mandate to strengthen the nation's scientific enterprise while advancing understanding of fundamental ecological problems.

Abstract

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.- subawards are planned for this award.