Herbivore-Ecosystem Interactions

Science Center Objects

Data from these studies help inform management decisions regarding ungulates on public lands, typically in large, jurisdictionally complex landscapes. Recent work involves investigations on the effects of herd size and movements of elk, bison, and wild horses on various ecosystem components. Specifically, scientific efforts include quantifying interactions among herbivores, plants, and soils; determining the effects of ungulate herbivory on ecosystem processes and vegetation communities; testing survey techniques for more accurate population estimates; and evaluating contraceptive methods for managing wild horse populations.

Image: Feral Horse (Equus caballus)

Closeup of a feral horse with its head turned, standing in a field. Public domain.


Wild Horse and Burro Population Management - Principal Investigator - Kate Schoenecker

Wild horse populations often increase at high rates on U.S. western rangelands, which in turn can lead to habitat degradation. The U.S. Geological Survey and the Bureau of Land Management are cooperating on studies investigating the potential of fertility control drugs to reduce foaling rates. In addition, because nearly every management issue concerning wild horses depends on accurate herd counts, USGS and BLM are testing several techniques that could improve population estimates and provide defensible error estimates (confidence limits).




Climate Change and Elk Herds

A herd of elk at sunset. USGS photo.

Elk and Bison Grazing Ecology in the San Luis Valley, Colorado - Principal Investigator - Kate Schoenecker

Managers need information on the grazing ecology of bison and elk in the Great Sand Dunes National Park and Preserve to develop science-based management alternatives. This study will determine elk and bison population status and movements, effects of herbivory, and suitable habitat and population potential in the park. From these data scientists will develop an elk/bison grazing model that includes grazing as a significant natural ecological process and protects sensitive native plant communities. The study will also provide information for developing a predictive model to be used in a planning process for management agencies, and includes monitoring the effects of treatments and new experiments on the distribution and movements of elk.



Wild horse herd

A wild horse herd aerial photo. USGS photo.

Non-invasive Genetic Sampling of Free-roaming Horses to Estimate Population Size, Genetic Diversity, and Consumption of Invasive Species - Principal Investigator - Kate Schoenecker

Molecular tagging is a new application of molecular genetic techniques to traditional mark-recapture methodology designed to address situations where traditional methods fail. In such studies, non-invasively collected samples (such as feces, feathers, or fur) are used as a source of DNA that is then genotyped at multiple loci such that each individual animal can be uniquely identified. Thus, each individual’s DNA represents a unique tag analogous to a band or other mark used in traditional mark-recapture studies.