Feral Horses in the U.S. – Indigenous or Invasive

Feral horse (mustang) herds roaming the Great American Plains are a well-known symbol of American history. Yet few are acquainted with their convoluted history and the socio-political and environmental conflicts they are involved in. The horses of today originated in North America but went extinct in prehistoric times due to unclear reasons. They disseminated to other continents and were reintroduced to North America by Columbus’ men. The period of the horses’ historical absence from North America has sparked debates as to their official status. Some horse advocates and environmentalists argue that feral horses are native to the continent and as such should be protected and given free space to roam. Their main arguments are that horses originated on and inhabited the continent long before humans started populating it, and that the feral horses of the Wild West are a national symbol of history and pride. Others, mainly farmers and agriculturalists, push for population control and limiting the mustangs’ area because they are an invasive non-native species that harms natural ecosystems and competes with livestock for resources. The U.S. Bureau of Land Management is responsible for implementing policies concerning feral horses. Currently, following the Wild and Free-Roaming Horses and Burros Act of 1971, the Bureau captures feral horses and gives them away for adoption. The main issue facing the Bureau is the legal and environmental status of feral horses as an indigenous or invasive species.

I. Introduction:
It is taken for granted that mustangs, or feral horses, have been roaming the Great American plains since the dawn of time while in scientific truth they evolved in North America, were forced into extinction and were brought back to the continent by the Spanish conquistadors. The reintroduction of the horse species has spawned two distinct conflicts: first, a scientific dispute as to the genealogical time periods of North American horses; and second, a policy cleavage as to whether the feral horses are an invasive species or one in need of protection. Modern academic journals and articles have focused on these two areas from a scientific and social point of view. As such, the mustang is no longer limited to a galloping role in epic westerns; it is both a topic of historical interest and a controversial issue for the U.S. public and legislators. When the status of feral horses as indigenous or invasive is firmly established by law and science, legal loopholes as well as the cleavage between environmentalists and farmers will be eliminated. II. Major Findings: 1. Horse History: a) Emergence and Disappearance in North America
Horses have inhabited the “New World” far longer than humankind. Fossil evidence suggests that horses evolved around 55 million year ago in North America, spanning multiple species and subspecies. North America was one of the first isolated continents, much like Australia nowadays; this circumstance facilitated the emergence and development of various species. Thus, the first “Eocene” horses (50-56 million years ago) lived undisturbed and interacted with the flora and fauna of the continent. From housecats with almost no hooves and forest browsers horses have evolved into large one-toed grazers with diverse diets. During the Miocene epoch when “forests gave way to springing grasslands the horse genera diversified and colonized this new biome (Haemig 2012)”. During the Pliocene (4.5-1.8 million years ago), just before the Ice Age, only one genus (Equus) out of five survived, and the horses of today genetically diverged from zebras and donkeys (Steiner & Ryder 2011). The only surviving genus in the world is the “Equus”, which first appeared during the North American Pliocene and is most similar to modern horses. The Equus spread across the entire continent (MacFadden 1994) but owing to the geographical isolations and barriers around the North American continent, it did not inhabit other continents. Similar to the present-day kangaroo, the horse in prehistoric times used to be an endemic species. The earliest horse of this genus was called “Equus simplicidens”, i.e. the most primitive type, from which modern-day horses further evolved.
At the beginning of the current Holocene period we live in (it began about 10,000 years ago) the Equus genus became extinct in North America. The reason for this has not been established yet but various theories suggest that climate change, overhunting by humans or a combination of both factors caused this. The climate alterations are supposedly also responsible for the extinction or decline of several plant species, which may have in turn led to the extinction of the horse species in North America altogether (Grayson 2007).
According to the alternative hypothesis, humans started peopling the continent roughly 14,000 or 13,000 years ago and overkilled the horse species. The most widespread (though recently challenged) theory holds that Ice-Age hunters from Siberia crossed the Bering land bridge (which had frozen over and was exposed to the surface at the time) into present-day Alaska or navigated with their boats around the coast (Curry 2012). This occurred a few thousand years ago before the last horse species disappeared from North America. Instead of domesticating the feral mammals, humans probably hunted them down for their meat since the hunter tribes of that time had not yet reached the nomadic stage of evolution. The new highly advanced and intelligent species (humans) coupled with unfavorable climate conditions may have driven horses to extinction.
Nevertheless, prior to their disappearance some horses managed to migrate to Eurasia via the same route that humans used to reach North America – the Bering land bridge. Around 11-10 million years ago the first horses spread though Asia and later Europe (Olsen 2003). Horses roamed the steppes and developed into modern-day domesticated horses. “A prime candidate for this locus [when and where horse domestication occurred] is the Eurasian steppe, specifically the Botai culture, northern Kazakhstan, in the mid–fourth millennium B.C.E., where faunal assemblages consist almost entirely of horse remains (Outram et al. 2009).” Afterwards, horse domestication and cavalry units became increasingly popular in Eurasia. b) Re-introduction of Horses into the New World
In 1493, with the second sailing of Christopher Columbus, Iberian horses were brought to the Americas (Christina Luis et al. 2006). Through the rapid colonization by the Spanish conquistadors, missionaries and later agriculturalists, horses rapidly spread across the Americas – some were domesticated, others turned feral (Sponenberg 2011). In addition to this, native tribes adopted the horse as a means of warfare and became warrior nomads, thus changing both their interaction with the European migrants and the distribution of horses. Native Americans would catch strays from the herd or steal horses from the settlers and breed more (Wissler 1914). Other Spanish horses (Equus Caballus) were sometimes lost, became feral and formed large herds that spread and migrated throughout the Great American Plains. They came to be known as mustangs – from Mexican Spanish mestengo "animal that strays" (16c.), from the Spanish mestengo ("wild, stray, ownerless"). The word literally stands for "belonging to the mesta,"an association of cattle ranchers who divided stray or unclaimed animals that got "mixed" with the herds, from Latin mixta "mixed" (Etymonline). 2. Invasive or endangered?
Policy- and society-wise the American Mustang subspecies is a source of opinion cleavages, especially in the Western United States. Although it is sometimes called “wild” (Equus ferus), i.e. never having been domesticated by humans, it should actually be termed “feral” (Equus ferus caballus). In other words, it had once been domesticated but due to circumstances lives free in the wilderness nowadays. The only living subspecies of “wild” horses is the so-called Przewalski's horse which is native to Central Asia while the mustangs in the United States descend from the once-domesticated Spanish horses of the conquistadors (Kavar & Dovc 2008).
Another issue regarding the status of the American mustang is whether it should be considered an alien or native species. If deemed invasive, the feral horses will suffer more stringent population restrictions by the government and more hunter freedom provided to the locals. If it is officially denominated as native, it will be protected by government statutes from hunters, agriculturalists and farmers. Cultural perceptions and political swings combine to shape the policy formation on the feral horse issue. c) Threat to Livestock and Ecosystems
The main argument put forward by locals and government officials is that feral horses are wide-ranging grazers that may dominate and damage grasslands as well as higher elevations unlike other cattle. “They damage landscapes by trampling vegetation, hard-packing the soil, and over-grazing (Beever 2004),” which in turn leads to decrease of plant species and brush cover where small reptiles and mammals typically thrive. Feral horses are much more prone to migration than other cattle and thus harm even larger spans of soil and a greater number of ecosystems than other similar herbivores. They are also “cecal digesters, which means that they are not selective in their forage” and they consume much more than cattle of equivalent body-mass (Beever 2003).
Moreover, feral horse populations have expanded dramatically in the last decades owing to governmental protection and/or negligence. Therefore, nowadays there are approximately 33,780 free-roaming feral horses in the western United States (Garrott & Oli 2013). Farmers have expressed fears that the situation, if left without supervision, will spiral out of control like it did in Australia, and damage plant species and livestock over which horses have a competitive advantage. There are currently more than 400,000 feral horses in Australia. They compete for food resources with cattle, “damage plants and water holes within national parks” and may cause the outbreak of equine influenza (horse flu) (Steve Csurhes et al. 2009).” Horses are highly adaptive and have come to occupy large and different ecosystems and although they have been designated as pests ever since 1860, little effort is put into limiting their numbers. Due to government non-interference, the horse population may have reached its maximum carrying capacity (Steve Csurhes et al. 2009). Thus, if the U.S. mustang population is not regulated, critics argue, it may bring down whole ecosystems when it passes the maximum carrying capacity as has happened in Australia. d) Need of Protection
On the other side of the fence are the environmentalists who are trying to portray the American mustang as a re-introduced and non-invasive species. If the demise of the species in prehistoric times was due to human interference, they argue, then the reintroduction of the horse re-establishes the ecological balance instead of disturbing it (Kirkpatrick & Fazio 2005). This stance portrays feral horses as the natural masters of the Western United States plains, and defines cattle and humans as the actual invasive species.
According to environmentalists, if the U.S. feral horses are not protected and preserved, they may be pushed once again to the brink of extinction which the so-termed Przewalski horse in Mongolia narrowly escaped. By the 1960s the Przewalski feral horse (also called takhi) had all but disappeared from the wilderness owing to overhunting, military activities and over-competition from domesticated horses and other livestock on the Mongolian plains (Boyd & King 2011). The takhi made it into the IUCN Red List of Threatened Species where it has been established as genetically almost identical to domesticated horses, much like the American mustang is biologically similar to domesticated horses (Kirkpatrick & Fazio 2005). The bigger picture, environmentalists argue, is that the economic short-term losses of farmers and agriculturalists today will be insignificant compared to the long-term investments required to preserve feral horses in the future if their population is negatively influenced by governmental or individual activity. There is no clear estimate of how much these fiscal investments are going to be but they will exceed the $72.4 million spent by the Bureau of Land Management (BLM) in 2012 on feral horse management activities (Gorey 2013).
Further arguments hold that the effects of livestock on local ecosystems are much greater than the negative influence that feral horses exert, simply owing to the greater number of domesticated cattle and the lack of regulations limiting their number. Livestock, much like feral horses, alter the species composition of communities (decrease biodiversity and species density), disrupt ecosystem functions (such as nutrient cycling and ecological succession), and alter ecosystem structures (contribute to soil erosion and water availability) (Fleishcner 1994). In addition, owing to their previously mentioned all-inclusive diet and greater adaptivity, horses generally utilize lands that cattle cannot access or avoid because of water scarcity (Budiansky 1997). III. Governmental Acts
The main federal actor in the debate is the Bureau of Land Management (BLM), a part of the U.S. Department of Interior. The Wild Horse Annie Act signed in 1959 by President Eisenhower was in effect the first act that banned the hunting of feral horses from aircraft or motorized vehicles on public land. Afterwards, the Wild and Free-Roaming Horses and Burros Act of 1971 (WFRHBA), signed into law by President Nixon, delegates the management of feral herds to the BLM. The Act outlaws the harassment or killing of feral horses and burros (donkeys) on federal land since these animals are “are living symbols of the historic and pioneer spirit of the West; that they contribute to the diversity of life forms within the Nation and enrich the lives of the American people; and that these horses and burros are fast disappearing from the American scene (WFRHBA 1971).” The official function of the BLM is to round up “invasive” herds of feral horses and give them away for adoption to either individuals or organizations. Nevertheless, recent rumors and news suggest that some of the adopted horses are actually sold to so-called “killer buyers” or slaughterhouses abroad, mainly in Mexico (Cohen 2013).
This legal loophole is the main issue that wild horse advocates and environmentalists raise in regard to the state of wild horse and burro herds. There have been numerous proposals and calls for amending the WFRHBA Act, among them the Restore our American Mustangs Act, which never passed through Senate, and Salazar’s proposal which aims to restore horse populations and the ecosystems they inhabit to a sustainable level (Gorey 2009). Neither act nor proposal has achieved any success so far. IV. Future Research: Native or Invasive in Law Statutes?
The main question that needs to be addressed is the environmental status of feral horses in the Great American Plains. They are usually deemed “non-native” by federal and state agencies because the Spanish horses that were introduced by Columbus’ men were a different species from the horses that initially populated the continent. This statement implies that feral horses are an invasive species that can be subjected to lawful extermination (Kirkpatrick & Fazio 2008). Scientists and legislators need to establish the environmental and legal status of feral horses once and for all and apply it universally. “[…] the two key elements for defining an animal as a native species are where it originated and whether or not it coevolved with its habitat (Kirkpatrick & Fazio 2008).” It can be argued from this that the horses originated and evolved in North America and that their period of extinction was due to human interference. Therefore, horses have a greater claim to the territory. If the horses are thus labeled as native, they will be protected from human harm and their populations will be sustained. This case, however, means that the BLM will need to come up with a modified, more cost-efficient and horse-oriented program that avoids legal loopholes and the inhumane treatment of the captured horses; shortly, it will need to exercise closer surveillance upon individual horses while at the same time cutting its expenses.
Legislators rely on scientists to provide them with the answers but the real challenge lies in overcoming the bickering of opposite lobbying groups. Scientists point out scientific evidence that establishes the biological similarity between the horses of today and the ones that originated on the continent but it boils down to the government to decide upon the legal status of feral horses. In short, politics and private interests must concede to scientific truth and objectivity. V. Conclusion:
The Equus genus originated in North America and managed to spread to other continents prior to its complete extinction from the continent. The reintroduced Spanish horses by Columbus repopulated the continent and were adopted by Native Americans or formed feral herds. These herds have sparked an issue of socio-political and scientific importance – whether the U.S. horses of today should be considered indigenous (and therefore be protected) or invasive (and controlled more strictly by the BLM). The issue was recently brought up in the news following the alleged killings of adopted feral horses (Cohen 2013). Since the government shutdown is over, the BLM is expected to resume its duties and maybe re-consider its program.
Whether or not the introduced Spanish horses were identical to the original North American horses is of little consequence to the feral herds of today. What is important is for these horses to be treated humanely and their populations to be sustained but not to the detriment of natural ecosystems and livestock. The BLM has to strike the balance between satisfying farmers and agriculturalists on the one side and environmentalists and patriots on the other. Feral horses represent a significant part of Wild West history and are emotionally related to American culture and values. Furthermore, they are an internationally recognizable symbol and one of the few half-wild species that are allowed to roam free in the wilderness. In the end, humans should remind themselves that the notions of “I came here first” or “I came last and this belongs to me” are equally ineffective and pernicious. By the same token, numerous human wars have been fought and lost on both sides. A war against nature translates into a war against ourselves.
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