A herder rides a horse as he tends his animals on grasslands located around 200km (62 miles) south-west of the Mongolian capital city Ulan Bator April 4, 2012. Mongolia remains the least densely populated country on the planet at 1.7 persons per square kilometer. The population of just 2.7 million people are spread across an area three times the size of France, with two-fifths of Mongolians living in rural areas. Picture taken April 4, 2012. REUTERS/David Gray (MONGOLIA - Tags: ENVIRONMENT)