Get reliable rangeland science

Understanding the ecological interactions of feral horse populations is of increasing importance on Western rangelands where management options are often case specific and complex. In the White Mountains, Arizona, USA, feral horse habitat overlaps heavily with cattle and other species of native ungulates including elk, mule deer and pronghorn. The addition of a novel large bodied grazing mammal within an ecosystem may have implications for both interspecies competition as well as for the soils and vegetative communities on which they graze. As is often the case, meadows and riparian areas are the focus of these interactions. To better understand grazing use and behavior we established a network of time lapse cameras and grazing exclosures to examine interspecies interactions as well as the intensity of grazing on two adjacent riparian study areas from May-October 2017. Photographic time series were used to examine both the fine scale spatial and behavioral relationship between grazers when they co-occurred as well as to explore the potential for more coarse scale temporal distributional strategies between species. We also used time lapse imagery to conduct a chromatic pixel analysis through R to establish a metric of seasonal forage availability as it relates to precipitation and ratio of greenness by image. Grazing frequency and species detection rates were compared with available forage using a simple linear model. To estimate forage utilization we established six 1m2 grazing exclosures at each site (N=12). We compared stubble height, species composition and dry yield to six randomly selected grazed plots within both study areas. Our study establishes base line information that can be used to inform feral horse management and design future hypothesis driven research to better understand the impacts of feral horses on rangelands. Preliminary results of this research are pending and will be presented at the time of the conference.