On a hot August morning, Mourad Gabriel steps out of his pickup onto the gravel road that winds up the side of Rattlesnake Peak. Dark-bearded and muscular, the research ecologist sports a uniform of blue work clothes, sturdy boots and a floppy, Army-style camo hat. He straps on a pistol. “Just to let you know,” Gabriel says, sensitive to the impression the gun makes, “it’s public land, so I open-carry.” Another 100-degree day is promised. Gabriel and his four fie…