Meet the giant hero rats training to sniff up Cambodia’s landmines

PHNOM PENH, Cambodia — A rat called Pit scampers back and forth between two handlers, running up and down the length of a measuring tape they hold between them. Suddenly he stops, stands on his hind legs and sniffs the air. Something is nearby. We wait. Finally he puts his paws to the ground and scratches the hot, Cambodian earth. Marking the presence of TNT.

Pit arrived in Cambodia in April. He is one of 15 African giant pouched rats who have been trained to detect landmines by Belgian non-profit organization APOPO at their Tanzania headquarters. This is the first time so-called “Hero Rats” have been deployed abroad.

“We believe the rats will increase the efficiency of our operations,” says Heng Rattana, director of the Cambodian Mine Action Centre (CMAC). “We are currently verifying the quality of their work.”  

Pit nibbles a rewarding banana. A handler runs her fingers along the measuring tape and notes the location of the TNT trace. If this were real life, a human deminer would return later and remove the mine.

Pit is hard at work, using his expert sense of smell to identify traces of TNT.

Pit gets extra marks for avoiding dummy scents. “We plant oil filters, tuna cans and coffee grains in the ground — all kinds of things to confuse the rat,” explains Hulsok Heng, supervisor of the Hero Rat program in Cambodia.

Cambodia remains riddled with landmines after decades of war. There are an estimated 4 to 6 million landmines and unexploded ordnances littering fields, forests and riverbeds. Explosive remnants have killed or injured over 64,000 people; the “vast majority” civilians, according to the Landmine and Cluster Munition Monitor. And, with over 25,000 amputees, Cambodia has the highest ratio of landmine amputees per capita in the world.

Serey Pov, a fruit seller in Phnom Penh, has a prosthetic leg after she stepped in a landmine back in 1993. She was lucky it was just the lower half of her leg that was destroyed. Now, from the way she moves around her stall stacked with pink dragon fruit, hairy rambutans and mangoes, you wouldn’t know.

Today, fewer people are experiencing the searing pain of amputation and the struggle of learning to walk again. In the last 20 years CMAC has cleared 2.6 million landmines and unexploded ordnance, according to Rattana. Casualty rates have fallen from 3047 in 1996 to 134 in 2013 — a record low. “We have received consistent support from the international community,” he says.

The rats will be a welcome addition to CMAC’s operations. While metal detectors beep for every coin, can and piece of foil in the ground, rats only locate TNT; so when they signal by scratching the ground, there is usually a landmine beneath. And they are speedy too. One rat can search 200 square meters in 20 minutes while a deminer with a metal detector can take 1-4 days to search the same area, according to James Pursey, APOPO’s communication manager.

Compared to sniffer dogs they are easy to transport, their diet of fruit and grains is cheap and they are willing to work with different handlers. “If a dog handler gets sick it would take one or two months to acquaint the animal with a new handler,” says Heng. “But the rats can transfer handlers easily.”  

While cheaper than advanced scanning systems it still costs over $6,500 to fully train one rat, according to the APOPO website. It’s important they are husbanded well so they live out their eight-year lifespans.  

Bred as-needed in APOPO’s breeding program in Tanzania, the rats begin training when they are five or six weeks old using a process called operant conditioning — being rewarded with favorite treats, like bananas and peanuts, when they successfully locate a target smell. As well as TNT, the rats have also been trained to identify tuberculosis in human sputum samples.

Pit was chosen for the demonstration at CMAC’s Siem Reap headquarters because he is a hard worker. According to Heng and his team, all the rats have different personalities. Some are industrious while some prefer to relax. Others have a prodigious sense of smell while others need more training.

A CMAC worker holds Pit after a day's work.

Despite initial positive results (Hero Rats have cleared over 18 million square meters of contaminated land in six countries, according to APOPO) others in the demining community have yet to be convinced. “Right now, we would not change to the rats,” says William Morse from the Landmine Relief Fund. “To take everyone and retrain them would be too costly and time-consuming.” For Morse, the big question is, if the rats are so effective, why aren’t millions of them being used around the world?

It’s because of funding, says Pursey. And the considerable bureaucracy that has to be traversed when sending rats abroad. After all, metal detectors aren’t subject to quarantine laws. 

Critics of Pit and his cohort are hard to find. “The rats have shown that they can contribute to the surveying and clearance of landmines,” said Chris Loughan, Director of Policy & Evaluation at Mine Action Group. “I would consider them part of our asset list.” 

Pit’s cage is in a cool room at CMAC. The training over, he scurries into a large clay pot and rearranges the straw inside. He’s nocturnal so he immediately curls up and squints his eyes shut. “I was amazed when I learned that rats could sniff landmines,” said Sean Enah, a rat handler who has over 20 years of experience clearing Cambodia’s minefields. “It’s good news for Cambodia and the people who live near minefields.”