Spatio-temporal Patterns of Resource Selection by Free-Roaming (Feral) Horses

Free-roaming feral horses ( Equus caballus ) utilize diverse rangeland environments throughout western North America. Even though horses are considered icons of western culture and a symbol of American pride, they are also shown to compact soils, alter plant communities, increase vulnerability to weed invasion, and reduce populations of competing wildlife. We sought to delineate home range boundaries, model horse herd distribution and resource selection, and validate the predictive performance of overall and seasonal models for horse bands living in the Sheldon National Wildlife Refuge (SNWR) in NW Nevada. Between 2009 and 2012, we collared 12 mares representing distinct horse bands using GPS trackers, collecting coordinate locations for each horse at 15-30 minute intervals. We produced 23 spatially explicit data layers to develop resource selection function (RSF) models using binomial regression. We used these models to identify the relative probability of horse use across the study area by season. The top variables for predicting horse use included distances to streams and springs, proximity to roads, elevation, and use of wet meadow and mountain big sagebrush habitats. We found that horses consistently select areas in close proximity to either stream or springs and wet meadows throughout the year and avoid mountain big sagebrush communities. The selection of stream and spring systems may exacerbate ecological impacts and outcompete wildlife in those areas. Many horses utilize areas near roads, likely for more efficient travel. These data can aid federal agencies and land managers responsible for horse populations and to help develop policy that identifies landscapes that are most important for ensuring healthy horse herds and conserving natural resources.