Tracking elephants as new railway cuts Kenya

Dangling from a helicopter with a high powered rifle, a Kenyan vet fires drugged darts at elephants to sedate them so they can be fitted with satellite collars. Ten minutes after the elephant is darted, the lumbering creature stumbles, and falls asleep. More than 12,000 elephants live in Tsavo Park, threatened daily by poaching, but also more recently, by the construction of a new high-speed railway linking Kenya's coast to the capital.