Dr. Karanth had been doubtful that this method was accurate so he tested trackers with a set of footprints made in a zoo. The big cats use trails through the forest. Automatic cameras set up along these known paths take pictures when an animal interrupts a beam of light. In order to trap animals he employs the historic techniques used in tiger hunting during the time of the Raj, with beaters and white cloth fences and hunters on elephant back -armed with tranquilizer guns. Captured tigers are carefully examined and measured, blood is drawn, and the radio-collars fitted.
Guards protect the tiger while still groggy to prevent attacks from other tigers.
Thereafter, the animal is regularly located and its wanderings plotted on a map. It will be followed by radio as long as the batteries in its collar last. Eventually, the collar rots and falls off. For each preserve, many unanswered questions remain. In much of Asia, commercial trade in tiger parts for use in traditional Asian medical practices is bringing tigers to the edge of extinction.