Tanzania-based NGO Apopo trains giant African pouched rats to sniff out land mines and detect tuberculosis. The initial stages of training for the TB- and mine-detection rats are fairly similar. When the rats are still pups, they are socialized to work with people.
The rats are then conditioned with clicker training, so that they associate the sound of a click with a reward (usually peanuts or bananas). They are then introduced to a target scent (TNT or positive TB samples).TB rats stay in the lab, where they are ultimately given multiple samples at one time to evaluate.
The training takes about six months. Mine-detection rats are moved first to a sandbox, where they are charged with sniffing out TNT-stuffed tea balls, before they ultimately train on a test field bearing both real and deactivated mines. Those rats can be fully trained in nine months to a year. (Source)