a herd of wild asian elephants has been at the center of public attention after they left their habitat in xishuangbanna dai autonomous prefecture in southwest china's yunnan province and started migrating north. firefighters like duan mengchao tracked them with devices including drones to guide them back home. after a 17-month journey, the elephants finally returned to their original habitat. check out the documentary series "a mammoth task" to see the process.
