Driving over the cattle guards that mark the boundaries of the Las Vegas Valley, Southern Nevadans are likely to come across an equine friend or two. Or a herd of them. Wild horses and burros, considered to be an emblem of the unconquerable American West, have been a permanent fixture of the Great Basin and the Mojave Desert for centuries. They roam Nevada’s sprawling public, federally owned lands, of which the state has the highest percentage in the nation.