Back in the 1970s, American scientists have found that laboratory rats are able to distinguish the smell of explosives. These rats breed well in captivity, learn quickly, and live up to eight years. They are resistant to diseases and have excellent hearing and sense of smell. And even if they step on a mine, their weight is so small that the munition will not explode.
After the first successful experiments, the local agro-university opened a "rat school", where they teach rodents to be sappers. The classes are conducted on a special testing ground: they burry mines and let the rats explore the field, holding them at a special leash like a dog. If rodent behaves unconventionally, is worried, or spins in one place, digging the earth this is a signal that the mine is detected. For each finding the rat gets a reward: peanuts or a piece of banana. Interestingly, but during the real work the immediate reward is not allowed, because the exact location of the mines is not known, and the place should first be examined by real engineers. But if an animal is mistaken and gets a reward, later on it starts to cheat, giving false signals.