Bighorn Sheep in Dinosaur National Monument

Bighorn Sheep ram closeupOriginally established to protect paleontological resources, Dinosaur National Monument was expanded in 1938 to include the Green and Yampa River corridors, and the bighorn sheep population that occupied them. It is a population with an unsteady history. By the early 1940s, bighorn sheep were extirpated from the Monument through overgrazing, disease, and hunting. Reintroduced in 1952, bighorns thrived initially, but then languished after a period of decline in the mid-1970s. Following releases of additional animals in the 1980s and 1990s, the herd again expanded, but current numbers and distribution remain largely unknown. Monument managers need better information about herd size and distribution, as well as factors that might limit population growth and expansion into new areas. This project is focused foremost on documenting seasonal ranges and travel routes, evaluating patterns of habitat use and selection, and modeling bighorn-habitat relationships to predict the distribution of suitable habitats. Relationships between bighorn distribution and the presence of domestic sheep on federal lands adjacent to the Monument are a particular concern. In addition, this project provides an opportunity to study genetic diversity in a population whose founders were drawn from diverse sources, and to test for possible exposure to a range of diseases that might limit population growth.

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