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Bees, Giant African Rats Used to Sniff Landmines

Maryann Mott
for National Geographic News
February 10, 2004
 
Dogs have long been used to sniff out land mines in war-torn regions.
But now they may have some welcome competition: rats and bees.

A Belgian company has trained African giant pouch rats (Cricetomys gambianus) to locate buried bombs, while researchers at the University of Montana are using honeybees to screen large areas for unexploded ordinance.

The efforts highlight the quest to find low-cost alternatives to safely detect underground explosives.


An estimated 80 million mines lay buried in more than 60 countries. Each day 50 people, many of them children, are killed or injured, according to the Landmine Survivors Network in Washington, D.C., an organization that provides peer counseling and prosthetics to victims throughout the world. The cost in human life is compounded by mines' impact on regional economies, where land is put off-limits to farming and development.

In Mozambique, an African country littered with land mines from decades of civil war, 20 rats were recently used to search for explosives. So far, they've been successful. In November, the animals found nine mines in one day along the Limpopo Railway, says Bart Weetjens, director of APOPO, the Belgian research company that trains the animals.

The Mozambique National Demining Institute accredited the technology in late September, allowing for the work to take place. Weetjens notes this is the first time the African giant pouch rats have been deployed in real mine fields.

The rats combed three minefields along a rail line that connects the port city of Maputo with neighboring Zimbabwe. Despite the railway's economic importance, few trains travel this dangerous stretch. People fear vibrations caused by trains will trigger the instable explosives.

Cheaper Than Dogs

APOPO came up with the idea of using rats while searching for a cheap and efficient way to detect mines. A trained rat costs about U.S. $2,000—about $10,000 less than a mine-sniffing dog. Other advantages include the rats' relatively small size (15 inches/40 centimeters), which make them easy to maintain and transport; their resistance to most tropical diseases; and their highly developed sense of smell.

"Rats are able to detect most types of mines," said Weetjens. "In principle they could detect all mines because of the explosive content, if it weren't that some devices have been manufactured with accurate sealing, which leaves no escape for explosive trace vapors. But these can easily be found with a metal detector."

Rats conditioned to TNT odors are trained to walk on a leash, which is attached to a bar that moves forward into a suspected field. When the animals smell explosive material they scratch or bite at the location. The rat's light weight—one-and-a-half to three pounds (0.7 to 1.5 kilograms)—does not trigger the mine.

A rat and handler can search 180 square yards (150 square meters) in about half an hour.

"After that, reliability of concentration for rats as well as trainers goes down," Weetjens said. This isn't a problem, he notes, since well-rested, replacement rats are available.

Currently the company has more than 100 rats in different stages of training at its facility in Tanzania, north of Mozambique.

Rats begin training at the age of five weeks when juveniles are weaned from their mothers. A positive reinforcement method known as clicker training is used. When the animal does something right, the trainer clicks a small, handheld noisemaker before giving the rat a piece of banana or peanut as a reward. (The same method is often used in America to train dogs in obedience schools.)

The company says the rats learn the desired task relatively quickly—between six to ten months.

"We now have some fourth-generation domestic animals. And generation after generation, the animals learn faster," said Weetjens. "It is too early, though, to conclude if this is due to selective breeding or to a more established training method and [increased] skills of the trainers."

After an animal has been fully trained, a series of blind tests are conducted during a six-week period. If the rat passes, it is then licensed for de-mining operations.

APOPO plans to use its trained rats elsewhere, including Angola, Cambodia, and Bosnia.

Bees and Bombs

Meanwhile, University of Montana researchers in Missoula have trained honeybees (Apis mellifera) as an efficient and low-cost means to screen large areas for hidden explosives.

The researchers note that most landmines and buried unexploded ordnance (UXO) leak explosives into the environment. During their tests, honeybees swarmed areas where explosive residue was present.

The insects had a 98 percent success rate in tests performed last year. Researchers said the location of the residue can be mapped to provide a picture of the extent, location, and density of bomb-contaminated areas.

"The beauty of this approach is that bees are indigenous to every climate on Earth, and there are beekeepers everywhere," said Susan Bender, a chemist at Sandia National Laboratories in Albuquerque, New Mexico, who worked on the project.

"You wouldn't need a million-dollar piece of equipment and extensive training to use it," she said. "The countries where landmines are a problem typically don't have those kinds of resources."

A hive of 40,000 to 65,000 bees costs around U.S. $100 and can be trained in as little as two hours, according to researchers. Now funding is needed to go to the next step, Bender said, so tests in a real mine field can be conducted.

Bee colonies can also signal other environmental anomalies, including chemical weapons attack, through electronic counters that monitor the number of bees exiting and entering a hive. Unusual activity signals environmental change.

Samples collected from hives, like wax, honey, and pollen, can also highlight environmental contaminants in an area.

Training bees is similar to training dogs. Bees are conditioned to associate an odor, such as the explosive materials TNT, DNT, and RDX, with a reward. In practice sessions, a sugar-water feeder and traces of explosives are set up near a colony. As the bees feed, they begin to associate the explosive's odor with the food source.

As foragers, the bees will search an area for similar odors and continue to look for hours, or even days, with appropriate reinforcement.

Bees also train each other. For example, if multiple hives are needed in a large area, only one needs to be trained. Researchers say the bees from the trained hive will naturally recruit and teach others.
 

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