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Feral vs. wild horses

 

The question of whether mustangs in the West are feral versus wild is a controversial one; it’s got a knack for appearing in the comment section of many a mustang story. Mustang advocates are adamant the wild horse is a bona fide North American wildlife species – on par with deer, elk, bison and pronghorn. Scientists, ever the party poopers, beg to differ.

Horse evolution is well documented in North America’s fossil record – first as a small dog-sized animal that walked on five toes over 50 million years ago, on to larger equines that bore their weight on single hooves. Horses went extinct on North America some 12,000 years ago – likely due to some cocktail of climate change and overhunting by man – but not before they migrated over the land bridge into Asia (where they further diversified into asses and zebras).

Despite their extinction on North America, horses guaranteed themselves a permanent spot in history when humans domesticated them some 4,000-5,000 years ago on the Asian steppes (possibly earlier). A partnership was born, and equines became a catalyst for human migration (and war).

Once domesticated, horses carried Gengis Khan’s empire into power. They were painted by Egyptians, Romans and Greeks. They bore the weight of the Crusaders on their backs (nobody said being friends with humans was easy). And 500 years ago, Spanish conquistadors couriered horses back to their evolutionary homeland aboard ships. Some escaped and became the seed stock for what would become a burgeoning wild horse population.

But are the horses here today the same animals that left 12,000 years ago? That is, how much did horses change in the 4,000-5,000 years since they were domesticated?

In wild species, nature selects for traits that best equip an animal for survival. But when humans are involved, we select for traits that meet our needs – a practice dubbed selective breeding. A new study in Nature suggests that by domesticating animals (dogs, in this case), we actually cause changes in their genetic hardwiring.

Selective breeding is generally obvious to the naked eye -- no need to zoom-in on genetics. Take a golden retriever for example. Its wild ancestor (by tens of thousands of years) is a wolf. Generation after generation, humans selected for the traits they desired: a caramel-colored coat, a can-do attitude, and an endearing tendency to slobber. Likewise, horses brought to the Americas by Europeans were purposefully sculpted beasts of burden.

Today’s wild horses often exhibit certain breed characteristics: Oregon’s Stinkingwater Herd Management Area (HMA) has a noticeable influence of draft horse; many of Wyoming’s HMAs are notorious for paints. Despite living in the wild, their domestic origins are clear.

One equine geneticist, Dr. Philip Sponenberg of Virginia Tech, points to color as a prominent indicator of mustangs’ domestic origins: wild populations generally have a single color and no white markings, he told me.

In North America, most native fauna are brown (think of deer, elk, bison, etc.). White isn’t an advantageous color in the wild (well, not in North America anyway) – but to humans who adore unique markings, perhaps it’s irresistible. Many mustangs bear white snips, stars or blazes in addition to sporting a variety of coat colors: palomino, sorrel, dun, grulla, chestnut, bay, and so forth.

A lot of mustangs don’t behave entirely like wild animals either (though this varies depending on the HMA). In the Pryor Mountains of Montana, for example, the Bureau of Land Management posts signage asking visitors not to approach the horses – because visitors can approach the horses. That approachability is a non-reversible remnant of domestication.

While science has soundly established that America’s mustangs are feral, not wild – the issue of whether horses are a native species keeps cropping up among mustang advocates.

Dr. Jay Kirkpatrick is one of the few scientists to strike a middle ground on the issue. He calls horses a “reintroduced native species” – but also says that it doesn’t matter which biological category you put them in (feral or wild), their fecundity begs for outside management. Though horses evolved on North America, today their population is no longer naturally controlled. Left alone, modern horse herds can double in size every 4-5 years (where are those darn saber-toothed cats?). Kirkpatrick is a pioneer in wildlife contraception, and has already shown that birth control can be an effective means to control wild horse numbers (read more about his work on Assateague Island).

So does the label really matter?

Some advocates argue it does, feeling that formal designation as a native North American species would entitle mustangs to more stringent protection.

In his HCN feature story, “Nowhere to run,” author Dave Philipps describes mustangs as “technically feral, non-native transplants like hogs or knapweed,” but notes that their relationship to humans and history makes them different than other invasive species.

“Centuries of living alongside people in the West had made [mustangs] an emblem of the wide-open landscapes, and of the grit, defiance and hardiness that Americans still believed defined their nation.”

Even though mustangs are not a native wild species – they are feral – most will agree America’s mustangs are a species of cultural importance, and one that deserves protection as such.

Monica Gokey is finishing a master’s degree in journalism at the University of Montana. She is producing a radio documentary on mustangs in the West, with a focus on the Pryor Mountain mustangs of Montana. In getting to know the horses, Monica has also gotten to know their cohort of people – an equally colorful bunch (she says that fondly).

Essays in the Range blog are not written by High Country News. The authors are solely responsible for the content.