Indeed, in a test in November along a southern Mozambique railway that was heavily mined during this country’s 17-year civil war, teams of three giant pouched rats found every one of 20 live mines in a previously unsurveyed 4,300-square-foot swatch of land.

“Animal detection, with dogs in particular, has increased very much in the last three or four years,” Havard Bach, the top expert on demining for the Geneva International Center for Humanitarian Demining, said in a telephone interview. But in many cases, he said, “it would probably be better to use rats than dogs.”

Rats are abundant, cheap and easily transported. At three pounds, they are too light to detonate mines accidentally. They can sift the bouquet of land-mine aromas far better than any machine. Unlike even the best mine-detecting dog or human, they are relentlessly single-minded…

Then there are rats, which don’t give a fig about people but will do anything for bananas and peanuts. “All a rat wants to do is find the target and get his reward,” said Mr. Bach, of the Geneva demining center. “They’re almost mechanical in the way they work.”