It is a high valley edged by serrated peaks, a remote expanse the size of Connecticut lying, as if forgotten, between two mountain ranges. Here, North America's tallest sand dunes blow against glacier-gouged summits, the Rio Grande begins its long journey from snowflake to saltwater, and vast reaches of desert scrub hide verdant pocket wetlands. Colorado's San Luis Valley is not a place for the timid. Sizzling hot in summer, frigid cold in winter, this huge landscape is humbling in its openness, a place defined by the rhythms of nature--and by the thrust and parry of male courting...