Management of Feral Horses in the National Park Service

Feral horses are considered non-native species within units of the National Park Service. Feral horse management actions depend heavily on whether they are considered desirable or detrimental within a particular locale. Public sentiment and population visibility has traditionally had substantial influence on actions taken. Author’s address: National Park Service, Biological Resource Management Division, 1201 Oakridge Dr. #200, Fort Collins, CO 80525; e-mail: jenny_powers@nps.gov.

1. Introduction

The National Park Service (NPS) was established nearly a century ago, with the creation of the Organic Act (1916), as an agency with a primary mission “…to conserve the scenery and the natural and historic objects and the wild life therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations” (16 U.S.C. § 1). The National Park Service General Authorities Act (1970) further clarified that “though distinctive in character, [Parks] are united through their interrelated purposes and resources into one national park system as cumulative expressions of a single national heritage; … these areas derive increased national dignity and recognition of their superb environmental quality through their inclusion jointly with each other in one national park system preserved and managed for the benefit and inspiration of all people of the United States…” (16 U.S.C. § 1a-1). Finally, the Redwood amendment (1978) further strengthened the assertion that all management would be consistent with the Organic Act and should be for “the common benefit of all the people of the United States” and that management “…shall not be exercised in derogation of the values and the purposes for which these various areas have been established, except as may have been or shall be directly and specifically provided by Congress.” (16 U.S.C. § 1a-1). 

Quite possibly one of the strongest underlying values the NPS embraces is the idea of “naturalness.” Although initially “naturalness” may appear to imply noninterference with the resource, active management is often necessary to address significant habitat and ecosystem changes associated with human influences. Sometimes intervention is necessary to restore natural processes. The NPS Management Policies (2006) directs managers to “...understand, maintain, restore, and protect the inherent integrity of the natural resources, processes, systems, and values of the parks while providing meaningful and appropriate opportunities to enjoy them. The Service recognizes that natural processes and species are evolving and the Service will allow this evolution to continue-minimally influenced by human actions.” The “natural condition” is one that describes the condition of the resource “that would occur in the absence of human dominance over the landscape.” Furthermore, “... in cases of uncertainty as to the impacts of activities on park natural resources, the protection of natural resources will predominate. The Service will reduce such uncertainty by facilitating and building a science-based understanding of park resources and the nature and extent of the impacts involved.” Likewise, the “Service will not intervene in natural biological or physical processes, except when directed by Congress; in emergencies in which human life and property are at stake; to restore natural ecosystem functioning that has been disrupted by past or ongoing human activities; or when a park plan has identified the intervention as necessary to protect other park resources, human health and safety, or facilities. Any such intervention will be kept to the minimum necessary to achieve the stated management objectives.” Finally, “All exotic [non-native] plant and animal species that are not maintained to meet an identified park purpose will be managed—up to and including eradication— if (1) control is prudent and feasible, and (2) the exotic species interferes with natural processes and the perpetuation of natural features, native species or natural habitats; damages cultural resources; or significantly hampers the management of park or adjacent lands...”.¹

Herein lies the conundrum. Equids evolved for millennia in North America but were extinct by the end of the Pleistocene, likely due to abrupt changes in climate and vegetation and coinciding with the immigration of humans to the continent.² Europeans re-introduced domesticated horses (Equus caballus) to North America in the late in the 15th century.³ Descendants of these domesticated horses lived for hundreds of years in direct contact with humans, including Native Americans and European immigrants, and were instrumental in advancing agriculture and transportation throughout the nation. Donkeys or burros (Equus asinus) share a similar introduction to the country, likely coming with Spanish explorers into the desert southwest early in the 16th century.³ As the country became more industrialized, horses were no longer relied upon to provide critical services for the developing country. Many horses were released or abandoned onto western range lands or remained as small remnant herds from early colonial exploration, homesteading, or ranching in areas around the United States.

Feral horses, ponies, and donkeys are found in several National Parks throughout the U.S. Currently, approximately 20 NPS units across the U.S. have horses or ponies and roughly 10 have burros. Population estimates on many NPS lands are unknown but likely total one to two thousand burros and approximately a thousand horses across the Service (all 401 NPS units within the U.S.) although historically there were substantially more.³ Feral equids residing within NPS units across the Service typically fall into one of four categories.

The first category includes animals that are resident within an NPS unit and are not specifically maintained or managed as a cultural resource. Often, these populations existed in the area prior to the establishment of a park. They may have been released in the area or migrated from another extant population. They have typically been feral for many generations. Management ranges from attempting to eradicate these animals from within a park, to no management at all, often due to lack of funds or resources. Concerns regarding resource damage (e.g., vegetation grazing, damage to historic structures, soil erosion, competition with native wildlife, etc.) range from minimal to significant, depending on the park enabling legislation (e.g., the document that describes the purpose of the park), horse use and damage to available habitat, interaction with other wildlife species, interaction with humans, and interference with park operations. Tools to remove animals include capture and live removal from the park for sale or lethal removal, if necessary. Examples include burro populations at Virgin Islands Coral Reef National Monument, VI and Mojave National Preserve, CA.

The second category encompasses trespass animals from publically managed herds on neighboring lands. The NPS often agrees to comanage these animals on the edges of their herd management units and manages horses similarly to the Bureau of Land Management (BLM) or the U.S. Forest Service. Management activities may include round-up and removal for adoption or participation in fertility control trials. Examples of parks with this situation are Bighorn Canyon National Recreational Area, MT, which shares management of the famous Pryor Mountain horse herd with the BLM, or horses on the periphery of Death Valley National Park, CA, which are managed similarly to the BLM strategies.

The third category consists of trespass livestock from privately owned property or tribal reservation property. The first priority for park managers overseeing this category is establishing ownership and notifying the responsible party that their animals are trespassing. Once ownership has been established, owners notified, and the animals are considered abandoned, a full range of management options are available from fencing, to round-up and removal, to lethal removal. Examples of parks with these circumstances are Big Bend National Park, TX, with trespass livestock from Mexico and Mesa Verde National Park, CO and Glacier National Park, MT, with trespass horses from neighboring tribal lands.

Finally, the last category of animals is the most popular, celebrated, and often controversial. These are horses and ponies that are maintained as desirable feral species as part of the cultural landscape of the park. These herds tend to be small, highly visible, and with many interested stakeholders. [...]