Home Archived April 13, 2016

Synecology of free-roaming ungulates on DOI landscapes


My research on free-roaming horses of the Great Basin initiated a precedent for extensiveness of study domain (>3 million ha) in which ground-based measurements are recorded and for comprehensiveness of sampling of ecosystem components (ants, soils, plants, reptiles, and small mammals), among such studies. Free-roaming horses and burros had engendered divisive conflicts among many, diverse interest groups. Lack of data fomented a culture of mudslinging across ten western U.S. states, and in areas having free-roaming equids around the world (Europe, Australia, South America). The research investigated which plant, reptile, and small-mammal species of the Great Basin exhibited lower abundance or density in horse-grazed areas, which species appeared unaffected, and which species exhibited higher abundance in horse-grazed areas. I and colleagues also addressed several issues at the nexus of basic and applied ecology, using sites from nine mountain ranges. These included the ability of any given ecosystem component to indicate changes in other components, tests of the Intermediate Disturbance Hypothesis, relationships to Greater Sage-grouse and their habitats, importance of direct vs. indirect effects of grazing, importance of scale, and the ability of different data sets to distinguish horse-occupied sites from sites that horses had been removed from for 10-14 years.

Other research across the western USA has investigated ecological consequences resulting from changes in grazing regime in systems with domestic cattle, free-roaming burros, or both.


National Research Council (G.H. Palmer [Chair], C.S. Asa, E.A. Beever, and 11 other authors). 2013. 2013. Using Science to Improve the BLM Wild Horse and Burro Program: A Way Forward. Washington, DC: National Academies Press.

Beever, E.A. 2013.Equus caballus [ISC]. Invasive Species Compendium, Commonwealth Agricultural Bureaux International, Wallingford, UK.

Beever, E.A., and C.L. Aldridge. 2011. Influences of free-roaming equids on sagebrush ecosystems, with a focus on Greater Sage-grouse. Studies in Avian Biology 38:273-290.

Connelly, J.W., S.T. Knick, C.E. Braun, W.L. Baker, E.A. Beever, et al. 2011. Conservation of Greater Sage-Grouse: a synthesis of current trends and future management. Studies in Avian Biology 38:549-563.

Beever, E.A., R.J. Tausch, and W.E. Thogmartin. 2008. Landscape- and local-scale responses of vegetation to removal of horse grazing from Great Basin (U.S.A.) mountain ranges. Plant Ecology196(2):163-184.

Beever, E.A., M. Huso, and D.A. Pyke. 2006. Multi-scale responses of soil stability and invasive plants to removal of non-native grazers from an arid conservation reserve. Diversity and Distributions12(3):258-268.

Beever, E.A., and J.E. Herrick. 2006. Effects of feral horses in Great Basin landscapes on soils and ants: direct and indirect mechanisms. Journal of Arid Environments 66(1):96-112.

Beever, E.A., and D.A. Pyke. 2005. Short-term responses of soil and vegetation to removal of feral burros and domestic cattle (California). INVITED article, Ecological Restoration 23(4):279-280.

Beever, E.A., D.A. Pyke, J.C. Chambers, F. Landau, and S. Smith. 2005. Monitoring temporal change in riparian vegetation of Great Basin National Park. Western North American Naturalist 65(3):382-402.

Beever, E.A., and P.F. Brussard. 2004. Community- and landscape-level responses of reptiles and small mammals to feral-horse grazing in the Great Basin. Journal of Arid Environments 59(2):271-297.

Several other authors and E.A. Beever. 2004. Sagebrush ecosystems: current status and trends. Pages 254-378 In: Connelly, J.W., S.T. Knick, M.A. Schroeder, and S.J. Stiver. Conservation Assessment of greater sage-grouse and sagebrush habitats. Western Association of Fish and Wildlife Agencies, Cheyenne, Wyoming.

Beever, E.A. 2003. Management implications of the ecology of free-roaming horses in semiarid ecosystems of the western United States. Wildlife Society Bulletin 31(3):887-895.

Beever, E.A., R.J. Tausch, and P.F. Brussard. 2003. Characterizing grazing disturbance in semiarid ecosystems across broad spatial scales using multiple indices. Ecological Applications 13(1):119-136.

Beever, E.A. and P.F. Brussard. 2000. Examining ecological consequences of feral horse grazing using exclosures. Western North American Naturalist 60(3):236-254.

Beever, E.A. and P.F. Brussard. 2000. Charismatic megafauna or exotic pest? Interactions between popular perceptions of feral horses (Equus caballus) and their management and research. Pages 413-418In: T.P. Salmon and A.C. Crabb, editors. Proceedings of the 19th International Vertebrate Pest Conference, University of California, Davis.

Beever, E.A. 1999. Species- and community-level responses to disturbance imposed by feral horse grazing and other management practices. Ph.D. dissertation, University of Nevada, Reno.