Abstract
Heavy grazing in riparian areas can lead to soil erosion, loss of bank stability, reduced infiltration, increased downstream siltation, reduced water quality, and drier, hotter habitat conditions. We investigated the impact of observed animals (wild horses, cattle, and wildlife) on riparian attributes (streambank alterations, stubble height, and utilization); and whether the presence of one animal species affect the presence or absence of another species. Prior research on wild horses has failed to address the potential impact wild horses may have on riparian conditions, which is important in the development of grazing permits and management decisions. To assess the impact of wild horses, we measured changes in streambank alterations, herbaceous stubble height, and forage utilization. At two study areas in Idaho, each study area had 4 stream reaches, at each stream reach we documented presence of wild horses, livestock, and wildlife with 16 game cameras. By using game cameras and measuring vegetation we are better determine each animal’s potential impacts on riparian condition. Many ungulates used our riparian study areas, including elk, pronghorn, mule deer, wild horses, cattle, as well as upland game birds, wolves, bears, mountain lions. Wild horse presence best predicted the change in riparian attributes (streambank alteration, herbaceous stubble height, and utilization) for five of six AICc models run. In only one occurrence did cattle presence predict change better than wild horses for utilization in the Owyhee study area. The potential impact of wild horses on riparian areas could compound known impacts from livestock. Thus, wild horses should be considered when determining management plans dealing with riparian condition.