Simulation of genetic change under four removal strategies for a wild horse population

Small and/or artificially reduced populations can suffer genetic erosion with long-term consequences to population fitness and persistence. However, managers must periodically remove free-roaming horses from the landscape to reduce the risk of habitat degradation. We developed an individual-based population simulation model to evaluate the expected change in genetic diversity after 100 years under each of four removal strategies for the wild horse population in the Pryor Mountain management area with removals occurring every 5 years, and assuming that no additional horses are introduced to the herd. We found that long generations and high survival rates of this wild horse population guard against rapid loss of genetic diversity for all scenarios in general. However, scenarios that included a removal strategy prioritizing individuals for removal based on relatedness initially increased mean genetic diversity that was subsequently maintained at a higher level than strategies that randomly selected individuals for removal.