Researchers in Tanzania have found that the three pound African Pouch Rat can be used to search for mines. The large (up to six pounds, and three feet long, including the tail) rodent is often domesticated (in Africa and elsewhere) and taught tricks.
The rats are taught, by repetition, to recognize the distinctive smell (metal, plastic and explosives) of a mine. When the rat finds one, they start digging, because they know they will be rewarded with a bit of food for doing so. The rats are light enough so they won't detonate mines, and are guided by a leash, attached to a wheeled metal rail, that is extended into the area to be cleared. The rat diligently covers all the ground it can reach, thus searching a path through the area that might be mined. Like most rodents, the African Pouch Rat has an excellent sense of smell and, so far, has detected all the mines in its path once it has been trained. The rats breed easily and are best domesticated if cared for by humans when they are pups. If well cared for, the rats live about eight years and enjoy repetitive tasks.
On the downside, a rat will only work for a few hours a day. But since many Africans keep the rats for pets or food, it's relatively easy to show people, in areas still heavily mined, how to train and use the rats for mine detection. One rat keeper can have several trained rats, and the rats will switch handlers more easily than dogs.