Wild and Free-Roaming Horses and Burros Of North America:

Factual and Sensitive Statement - How They Help the Ecosystem

By Craig C. Downer

A band of beautiful, light-colored wild horses in the Granite Range north of Gerlach, Nevada 


Origin of Horse Family and Horse Species

As proven by recent genetic analysis of partially fossilized remains, the species: Equus caballus itself originated in North America. It is common knowledge that the horse family lineage in North America dates from Recent times (ca. 10,000 years before present) to the very base of the common era, or Cenozoic, nearly 60-million years ago.

At the close of the Pleistocene epoch during the last ice age (ending ca. 12,000 years before present), many large mammal species died out in North America due to a combination of abrupt climatic changes and overkill by Amerindians.1 It follows that the natural comeback of the returned native horse in a large-mammal-depauperated North America is a benign reoccupation of an only recently disoccupied ecological niche and constitutes a natural restoration, including here in the West where I live. Similarly to the wild horse, the burro can trace its not-far-removed origin to North American, and in certain parts of this continent, such as the Southwest, wild ass fossil remains testify that a similar type niche to that of the burro was occupied. The wild burros naturally refill these vacant niches still in a few places permitted by authorities, but, unjustly, they do so at non-viable levels that are actually contrary to Public Law 92-195. This law should protect and provide for both them and the wild horses where they were found at the passage of this act in 1971.

A spirit band in a burned over area in the southern Pine Nut Range just SW of where I live in Carson Valley. This range has been largely cleared of its wild horses for unjust political reasons. 


During the course of the long co-evolution, referred to above, the horse family has developed many mutually beneficial relationships with the native plants and animals with which its members have coexisted for many millions of years. Indeed, the horse can stake the claim to being one of the very most ancient and longstanding members of the North American life community, more so than either the bighorn sheep or the bison, species whose origin was in Eurasia before they occupied North America after crossing the Bering Strait land bridge when oceans receded with the tie up of global moisture during the Ice Ages.2 The latter two species are, indeed, relative newcomers upon the North American scene, when compared with members of the horse family: Equidae, and the horse species itself, Equus caballus, which evolved to its present basic form here in North America, as most abundant fossil evidence most cogently prove.


Ecological Contribution of Wild Horses to Native North American Plants and Animals

Both horses and burros possess a caecal, or post-gastric, digestive system that does not as thoroughly decompose the vegetation these herbivorous mammals eat. Such a system allows the seeds of many plant species to pass through the gullet intact and ready to germinate in the soil that is then fertilized by the droppings of these herbivores. In this way, many plant species have been and continue to be successfully dispersed over large areas by wild equids. Since wild horses and burros roam over large home ranges, which themselves shift over the generations, each plant species thus dispersed is able to occupy its ecological niche over a more extensive geological area than it would were it not for the wild equids. And it makes sense that since North America is the evolutionary cradle of the horse family, which includes the burros, many such mutually beneficial (mutualistic) symbiotic relationships have evolved between the horse family in general, on the one hand, and the food plants that sustain them, on the other. This is a beautiful fact of life when we consider it from an evolutionary perspective. And it logically follows that if many native plant species are so benefitted by horses and burros in North America, then all the animals that depend in some degree upon these plant species are likewise benefitted, from fellow herbivores that consume the plants to predatory animals that consume the plant eaters, and on up the food chain.

A wild horse band at springtime in the Virginia Range, in the area of the historic Virginia City, Nevada


As concerns mutualistic relations, it should also be noted that horse feces contain less thoroughly decomposed vegetable matter than would a ruminant's and, for this reason, more greatly aid in building the nutrient-rich humus component of healthy soils. This leads to better water retention and nutrient level for root absorption, and the overall well-being of the horse/burro-inhabited ecosystem. It must also be noted that behaviorally wild horses and burros greatly aid their fellow animals in accessing both water and food both during freezing winter and parching summer seasons. This they do by dint of their strong bodies and hard soliped hooves. These allow horses and burros to break through frozen water sources or icy snow drifts and similar wintery situations. Many animals are not able to access food and water without the horses and burros with whom they have coevolved for, not just thousands but in many cases for millions of years! Similarly during the hot summers when water tables recede, the horses and burros can detect water far off through their keen olfaction, or sense of smell. After the humidity has led them to water, when necessary, they are able to dig down to adequate underground sources, or to similarly enlarge tiny seeps so that they can survive through the critical dry period of the year. This greatly benefits many other species of animals whose individual members would otherwise be unable to access water and would perish.


Upon reflection, it makes beautiful sense that the longer a given set of species of plants and animals have evolved together, the more mutualistic relations they come to establish. According to this solid naturalistic logic, America's last wild horses and burros count among the very most mutually integrated and ecologically valuable of species precisely because (1) North America is the horse family's (and even the modern horse species') ancient "cradle of evolution" and (2) horses and their kindred have among the very longest evolutionary histories of any species or related group of species here! And may God grant us the insightful and penetrating wisdom to appreciate the great spiritual as well as ecological and evolutionary significance in all of this, for these uniquely evolved, conscious beings are also our brothers and sisters in the higher, more all inclusive family of life!



1. Martin, P.S. & H.E. Wright. 1967. Pleistocene Extinctions, Yale Univ. Press, Hew Haven, CT

2. Benton, M. J. 1991. The Rise of the Mammals, Quatro Publishing, London


About the author:

Craig Downer, AB, MS, PhD is a Wildlife Ecologist and author of Wild Horses: Living Symbols of Freedom. ccdowner@yahoo.com