Mine-sniffing rats are the sole focus of Apopo, a Flemish acronym for ''product development geared toward the demining of antipersonnel mines.'' The group is the brainchild of Mr. Weetjens' brother Bart; a college friend, Christophe Cox; and a University of Antwerp professor, Mic Billet, now Apopo's chairman.

The three decided in the late 1990's that so-called biosensor animals with great noses were the future of land-mine detection, but that there must be creatures better suited for the task than dogs.

With a grant from the Belgian government, they began hunting for an animal with a dog's sense of smell, but none of its drawbacks. They approached Ron Verhagen, the head of the university's biology department, for help. ''And that,'' Mr. Weetjens said, ''is where rats came along.''

Specifically, along came Cricetomys gambianus, also known as the Gambian and African giant pouched rat. Up to 30 inches long, it thrives in most of sub-Saharan Africa, lives up to eight years in captivity and is ''savage'' in the wild, Mr. Weetjens says, but so docile when bred that some people keep them as pets.

Most important, the pouched rat (so named because it stores food, hamster-style, in its cheeks) buries what it does not immediately eat and sports a nose honed to bloodhound status by eons of searching for buried food stashes. Persuading him to hunt for land mines, therefore, is as simple as convincing him that TNT is just another tasty treat waiting a few inches underground.

The rats' journey from farm pest to minesweeper has not been without bumps. Apopo breeds and conditions the rats to associate TNT with food at a Tanzania site run by Mr. Cox. and Mr. Weetjens's brother Marc. Then they are sent to Mozambique, where training is financed by a Belgian government grant. The first batch died en route after being accidentally left for two days on a broiling Johannesburg airport tarmac. A second batch, born in the wild, were unmanageable. ''They'd bite you,'' Mr. Weetjens said. ''They'd climb over nine-foot plexiglass walls at night, and in the morning we'd find them on the floor, fighting.''

But the third, home-bred batch has mostly thrived.

Each rat gets to sweep a 10-by-10-meter square of land on which two defused mines or TNT scents have been hidden. Finding the mine or scent earns a click and a bite of banana or peanuts. Failure generally earns a second try. Some rats try to game the system, scratching the earth randomly in hopes of getting free treats. But the trainers feed them and sound a click to signal success only when they scratch the right spots.