By on August 1, 2010 in Wildlife

You Dirty Rat  

In the animal kingdom man and dog have enjoyed a long and cherished love affair. But man and rat? Not so much. When most people think of rats, images of famine, disease, the black plague, NYC and eccentric house pets come to mind. It is fair to say that throughout history rats have disturbed the human psyche.

Rats have ancestry that is traceable to the Paleocene epoch, dating back about 65 million years ago. This means that rats, albeit different versions than what we are used to today, inhabited the planet right after the extinction of the dinosaurs, making them one of the oldest species on earth. During the black plague in Europe, rats were blamed for the epic panic that enveloped Europe as entire villages were wiped out by the then mysterious disease. Several centuries later, the extreme sport of Rat Baiting emerged as one manifestation of our disdain for the animal genus Rattus. Gamers were known to place 20-30 terrified rats in a closed pen with a terrier, while wagering bystanders placed bets on the ensuing battle. More recently, in India’s northeastern state, Mizoram, rats ate the region’s entire paddy crop, resulting in severe famine for over a million people. With this legacy, the famous gangster refrain “you dirty rat” seems to succinctly sum up how most people feel about the long-tailed critters.

Nowhere is the rat hated more than in Africa. There, locals are highly suspicious of rats and blame them for the spread of disease and famine. However, thanks to some clever work being done by the African Giant Pouched Rat, the animals’ soiled reputation might soon be due for an overhaul.

Three Blind Rats  

The African Giant Pouched Rat (Cricetomys gambianus), can grow up to 9-pounds and can live in captivity for 6-8 years. The rats live in colonies in the wild, and are widespread across most of Africa, where they are also commonly eaten as bush meat. The rat is very fertile and females can have up to four litters of six little rats in a 9-month period. The African Giant Pouched Rat is nearly blind and is heavily reliant on its keen sense of smell for survival. Males are territorial and aggressive towards one another, but the rat is otherwise social and has recently become a favorite amongst exotic pet owners. Resistant to endemic diseases, widely available, and inexpensive to procure, the African Giant Pouched Rat has many positive attributes.

When Belgium native and product engineer, Bart Weetjens, made an analysis of the landmine problem in sub-Saharan Africa, and learned that the detection of the devices was difficult, dangerous, costly and time consuming, he decided to approach the problem from the viewpoint of the subsistence farmers, and the limited resources they have at hand. Bart had come across a research article published in the 1970’s on gerbils detecting explosives in a lab, and he remembered his childhood pet rats with their terrific sense of smell and trainability. To Bart, it was quite logical that his beloved rats could provide a cheaper, more efficient and locally available means to detect landmines than human specialists or detection dogs.


The initial research was carried out in Belgium in early 1998, with a group of African Giant Pouched Rats. Once domesticated, a training protocol was developed using the principle of positive behavior reinforcement (the rat does something right, they hear a ‘click’ sound and get a banana or some peanuts). Once “proof of principle” was achieved, the project was moved to Tanzania in 2000, allowing the rats to be trained in near-to-real conditions. Weetjens created the social enterprise APOPO, with a mission to “train detection rats to enhance life-saving actions.”  Today, APOPO is a registered charity in Weetjens’ native Belgium and is headquartered in Tanzania.

A human nose would have a difficult time distinguishing the unique smell of TNT, and yet the pouched rat is able to zero in on the ‘signature scent’ of the explosive, to which it is trained to react. This ability is called olfactory discrimination. The concept of explosives’ olfactory discrimination was actually suggested by an American publication in the 1970’s, but it wasn’t until Bart and his team found the African Giant Pouched Rat – with its long life span, trainability, and keen sense of smell – and took the research to the field, that proof of the rat’s capability in detecting landmines was established.

My Hero, the Rat

HeroRATs is the name now used for the rats that train under the APOPO team. They’re trained to respond to the scent of TNT in landmines, and to associate the smell with a food reward. Once the initial stages of socialization and pre-training are complete, the rats move to a training field about 24 hectares in size, broken up into more than 1,000 demarcated boxes. Here they run along a harness between two trainers, sniffing and scratching at the ground to indicate when they have found a landmine. The trainer gives the rat a ‘click’ sound for a correct indication, and the rat returns to the trainer for a food reward.

Once fully trained and in the real minefield, the rats wear a harness connected by long cords to two trainers. The trainers note the areas where the rats stop to scratch, and once the area has been covered by 2 rats, a team of professional deminers steps in to safely deactivate the landmines.

The project has been unbelievably successful, having returned more than 1.3 million square meters of land back to the population since the start of operations. In Mozambique’s Gaza Province, 44,547 people benefited from APOPO’s mine clearance activities in 2009. The HeroRATs also contributed to the successful clearance of a stretch of land near a Mozambique village that had been without electricity because power companies balked at the idea of building power lines in an area full of landmines. After the rats had completed their job, the village could be connected to the National Electricity Grid, bringing power to over 10,000 residents. In 2007, the International Conference on the Great Lakes Region (including Burundi, Rwanda, north-eastern DR Congo, Uganda and north-western Kenya and Tanzania) identified APOPO as the lead agency for mine action in the region, which comprises of 11 countries. A professional company of rats respected enough to patrol the land of 11 countries is about as probable as monkeys being hired to baby-sit.

Here They Come to Save the Day

APOPO is not stopping at landmines either. While future plans include sending the rats to Angola, and the Congo for de-mining projects, the NGO has even higher hopes.  

APOPO has recently put the rats to work detecting tuberculosis in human sputum samples. Globally TB is second only to HIV/AIDS as a cause of illness and death in adults, accounting for nearly two millions deaths every year. Tragically, TB is treatable with early detection and proper care. The rats are proving capable of finding the sputum samples that are positive for tuberculosis, and they can screen in seven minutes the same number of samples a human technician can screen in a full day. Animal lovers can rest assured; initial research, involving a group of rats that were exposed to the TB bacteria, indicated that the species is not susceptible to contracting TB.

With the HeroRATs successes piling up, the time may soon come that rats earn a makeover in the human imagination. It is obvious we learned our distrust of rats from the dark era of the Plague, when they were blamed for mass human casualty. But that was a long time ago. Now that they are proving to be such effective lifesavers, their role in human destiny appears to be going full-circle. Long live the rat!


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