1. Department of Fish, Wildlife, and Conservation Biology; Colorado State University; Fort Collins CO 80523 USA
2. U.S. Geological Survey; Colorado Cooperative Fish and Wildlife Research Unit; Department of Fish, Wildlife, and Conservation Biology; Colorado State University; Fort Collins CO 80523 USA
3. United States Environmental Protection Agency; Denver CO 80202 USA
4. Department of Integrative Biology; University of Colorado; Denver CO 80217 USA