That morning the rats finally got the hang of it. By 9 o’clock, when 30-degree Celsius heat forced a halt to the work, the rodents had managed to find nine mines. In the next eight days, the rats found a total of 22 mines–a success rate of 100 percent, as established by subsequent sweeps of the area with metal detectors. “We opened a bottle of champagne in the camp to celebrate,” says Weetjens. The rats got a few scrumptious bits of avocado.
Weetjens’s experiment is the first time rats have been used to find land mines. If APOPO can overcome some obstacles–including the animals’ sensitivity to temperature and climate–rats may soon take their place alongside metal detectors and dogs as standard tools in the dangerous, expensive and time-intensive work of humanitarian demining. That would be welcome news. At present more than 100 million land mines are deployed in 90 countries, and they kill or maim 40 to 55 people per day on average, according to Red Cross and RAND Corporation estimates. Combatants lay 40,000 new mines each year. At the present rate, it will take 500 years to remove them all, according to a recent RAND study. The need to quicken the pace of demining is urgent, and experts have come to believe that animals hold the most promise.
The traditional manual demining technique of sweeping the ground with a metal detector is tedious and inefficient, turning up hundreds of false positives–bullets or other scraps of metal–for every actual mine. Mine-sniffing dogs, introduced a decade ago, have produced a fivefold increase in speed, largely because they have fewer false positives. They’ve since become widely accepted by demining groups, with some 500 now deployed worldwide.
Although dogs are a big improvement, they’re no panacea. Oftentimes they get so excited over finding a mine, they tend to lose focus. Rats, on the other hand, are fixated on getting as much banana and peanut rewards as they can, which means they go from one mine to the next without skipping a beat. Unlike dogs, they’re too light to set off mines. And they’re better suited than dogs to repetitive work. Weetjens trained his rats to associate the scent of explosives vapors with a click sound and food. Later, he delayed the click, which made the rats bite or scratch at the ground to get their food reward–behavior that allows human handlers to pinpoint a mine’s location in the field. Weetjens estimates that a demining rat can be trained in three to four months–about half the time of a dog. And rat teams cost half as much as canine deminers to operate. “This is a promising development,” says Sara Sekkenes, chair of the International Campaign to Ban Landmines working group on mine action. “Getting cheaper and cheaper methods will eventually be what makes it possible to get a mine-free world.”
Dogs won’t be getting pink slips any time soon, of course. For one thing, they can cover more ground faster than rats, and in some countries they may be more culturally acceptable. Rats, on the other hand, may do better in densely mined fields, like those around Kabul, where dogs get easily confused. And rodents could be equipped with wireless cameras and sent into collapsed buildings.
Scientists have had some success in training bees to distinguish between mined and unmined fields, and one Israeli expert has trained mine-sniffing pigs. Weetjens is optimistic that his rats will generate enough interest for continued funding–he’s already heard from demining groups in Cambodia, Bosnia and Herzegovina, Sudan and Angola. Which means Jullie and her rat pals could soon be eating a lot more avocado.
