Predation of seeded species by Feral Horses and Burros

Authors: Clements, Darin; Harmon, Daniel

Submitted to: The Progressive Rancher
Publication Type: Popular Publication
Publication Acceptance Date: 2/14/2025
Publication Date: 3/10/2025
Citation: Clements, D.D., Harmon, D.N. 2025. Challenges in rehabilitating degraded Winterfat communities. The Progressive Rancher. 25(3):18-19.

Interpretive Summary:

Technical Abstract: In 1971, the Wild Free-Roaming Horse and Burros Act became law, placing the animals under the jurisdiction of the Secretary of Interior. This legislation was to protect and manage feral horses and burros to achieve and maintain healthy populations in balance with healthy ecological conditions on rangelands. Grazing by livestock, primarily cattle, is widespread on federally owned rangelands, which comprise about 70% of the 11 western states. Conservationists claim that many grazing practices result in ecological costs that include loss of biodiversity, reduction of plant and animal population densities, disruption of ecosystem functions, change in habitat characteristics and degradation of riparian ecosystems. For the restoration of degraded grazing lands, land managers attempt the application of large reseeding efforts to improve species composition and richness of desirable species to combat invasive weeds and provide perennial forage for livestock and wildlife. It is well documented that following these reseeding efforts, land managers restrict livestock grazing for a 2-year period to allow for seedlings of seeded species to establish on the site. Although domestic livestock are restricted from use in these treated habitats, other herbivores including rabbits, wild ungulates and feral burros and horses all can impact the survivability of seedlings of seeded species. We implemented an experiment in northern Nevada to test the efficacy of pre-emergent herbicides to improve the establishment of seeded perennial grasses. Initial monitoring in April 2022 recorded 7.2 perennial grass seedlings/ft², which dropped to less than 6/ft², yet the health of these perennial grass seedlings that were in the 3-4 leaf stage showed no signs of seedling desiccation. What we did notice is that a portion of these healthy perennial grass seedlings were actually pulled from the ground from herbivory activity, therefore we scheduled another perennial grass seedling count for mid-May. During our mid-May perennial grass seedling counts we recorded an additional mortality rate of perennial grass seedlings that went from 5.8 perennial grass seedlings/ft² down to 0.9 perennial grass seedlings/ft², an 86% reduction in just 2 weeks. Although feral burros were the main culprit to the heavy mortality of seeded species, it should be noted that feral horses and pronghorn antelope were also present on these treated plots. Resource managers tasked with improving rangeland ecosystems are faced with an uphill battle when discussing the reduction and management of feral horses and burros to aid in the recovery of arid and semi-arid rangelands. Furthermore, the restoration or rehabilitation of rangelands through reseeding efforts also face significant challenges if feral horses and burros are not managed at levels that significantly reduce mortality of seeded species.