African giant pouched rats are endemic to sub-Saharan Africa, they are used to the tropical climate and are resilient to many tropical diseases. Veterinary care requirements are therefore relatively small. Routine care includes daily observations of individual animals, weekly health reports and regular prevention treatments for parasites.
During the week, trained rats live on a reward diet that consists mainly of bananas and peanuts. On the weekend, they eat a balanced diet of grains, maize, nuts, vegetables, fruits, fish and sometimes insects. This is also the permanent diet for the breeding rats, but during weekdays they get additional fruits and vegetables (e.g. Monday tomatoes and eggplant, Tuesday sweet potatoes and watermelon, etc).
APOPO has a breeding program which supplies rats ‘as needed’ for the training, research and detection programs currently underway. We have breeding couples and successfully trained rats that are taking a ‘work holiday’ also participate in our breeding program. Sometimes additional wild rats are introduced into the breeding program (to scale up productivity). In the early days we attempted to use wild-caught rats, but it became clear very quickly that it was not going to work. The rats were aggressive and just could not be handled. Now we breed the rats and begin handling them and exposing them to all kinds of objects, sounds, and smells as soon as they open their eyes, at about four weeks of age. When the rats are raised in constant contact with people, they are very easy to handle and train.
The HeroRATs in training share kennels with their siblings. The kennels are cleaned regularly and the rats have their own caretaking staff who make sure they are fed, loved, have access to drinking water, and clean living quarters. As other captive-born rats, the HeroRATs enjoy attention, including being petted and taken out for playtime. APOPO has several outside pens where the rats can play and get used to an outside environment. The breeding enclosures are designed to simulate the native habitat of the rats, complete with dirt to make tunnels and create living chambers in.
Routine care includes daily observations of individual animals, weekly health inspection and reports and regular prevention treatments for parasites. Every two weeks a vet visits the training and breeding facility to check on the animals. The rats eat a well-balanced diet and we make sure that they have plenty of time to relax and play in between the training and work sessions.
The majority of our rats live to the end of their expected life-span. None of our rats have ever died as a result of their detection work.
We have been operating in TB and demining for long enough now that some of our rats have reached retirement age, which is typically between 7 and 8 years of age. We allow them to work as long as they are performing well, still feel like working and pass weekly health checks. We notice that the rats are generally enthusiastic to get to work but when they are growing old, some simply don’t feel like getting out of their cage to work anymore. If that happens or when a rat’s performance has declined or it is not healthy enough to continue working, the rat is retired to its home cage. When they are retired to their cages, they receive a healthy diet, are regularly taken out to play and exercise, and continue to receive weekly health checks. If a rat is clearly suffering in its old age or from an untreatable disease, it is humanely euthanized.
The bedding we use in the cages is composed of a variety of non-aromatic hardwoods, no softwoods and definitely no pine and cedar (those are the ones that are known to be dangerous). The rats also have an excellent health record, and respiratory problems are basically nonexistent, so we are confident that the bedding is safe.
The rats are nocturnal and susceptible to developing skin cancer on their ears. We train the rats very early in the morning and stop before the heat of the day can affect them, but they sometimes develop cancer despite our attempts to prevent it. If they do start to develop skin cancer, we apply a salve to reduce any itching or discomfort, but if the problem becomes too serious we take them to the vet where the affected areas are surgically removed under local anesthesia.
Demining is a dangerous job and, sadly, human deminers are sometimes injured or killed. The rats have a significant advantage over their human demining partners in that a pressure-activated antipersonnel landmine typically requires about five kilograms of pressure to be activated. Our heaviest operational male rats do not exceed 1.5 kilograms and are, therefore, in no danger of activating this type of landmine. However, working around landmines is dangerous work for anyone involved. Fortunately, no rats have been injured or killed in the minefield to date.
Our rats work Monday through Friday and play and rest on weekends. During weekday mornings, landmine-detection training at the field takes place between 6:30 am and 8:30 am. Each rat has a short training session of about 20 to 30 minutes and spends the rest of the time waiting in its transportation cage in the shaded with plenty of water. Afterward, the rats are returned to their home cages and the trainers take a tea break at the office. Following tea break, our training team breaks off into smaller teams to handle special activities ranging from maintenance of the training field, animal health and welfare inspections and cage cleaning, to taking rats to the play cage area for daily exercise. The trainers also work in short sessions with our younger Mine Detection rats and TB-detection rats in the respective centers. This often includes training with the youngest rats that are just beginning socialization. After lunch, the trainers wrap up all training activities and prepare for the next day’s work.
Fortunately, very few rats fail to progress through training, but it does happen. We are dedicated to helping people and saving lives with the rats, so if a rat doesn’t hold promise to contribute operationally, it is transitioned to another training or innovation project or given an early retirement (cared for in its living cage). From our experience, a rat that struggles in one task can be very successful in a different one, so we always try to give the rat a chance to show off its talents and contribute to our humanitarian efforts in another way.
APOPO trains the rats using operant conditioning to shape and reward behavior with a handheld clicker and food rewards. Training begins with socializing the rat to humans when its eyes first open around 4 weeks old. During this socialization process, APOPO’s trainers introduce the baby rats to the sights, sounds, and textures of the human world. The young rats are later weaned from their mothers at 10 weeks and begin clicker training, where they learn to associate a click sound with a food reward – usually a nutritious mix of mashed banana, avocado, and rodent chow. Once the association is established, they are ready to begin training on a target scent of either TNT or TB-positive sputum. Once the rat learns how to signal to its handler that it smells the target odor, training complexity gradually increases to teach the rat to ignore irrelevant odors and to search for targets according to the needs of the operational environment. This training continues until the rat passes a blind test to earn its accreditation.
Normally, the rats are trained about half an hour per day, five days per week. During the weekend, they relax and can feast on an extensive variety of fresh foods.
An exact cost calculation of the sniffer rats can be complicated and depends on relevant operational field experience over a period of time. However, at present we estimate that 6 euro per month covers basic nutrition, daily care, housing and healthcare for one rat. If you factor in all the variables that go into training, evaluation, and care, it costs an average of 6,000 euro to fully train one detection rat.
HeroRATs and their trainers
The HeroRATs can live up to 6 – 8 years. Conservatively, we estimate they can work in the field for up to 4-5 years.
The breeding couples generally have 2-3 litters each per year, with 1 to 5 pups per litter.
In APOPO’s experience, all staff members who have been employed to train the animals (mostly Tanzanians) have picked up the job quickly. There have been no cases of fear among the trainers or cases of mistreating or rough handling of the rats, behavior that could initiate fear in them. In general, we observe quite gentle handling and respectful interaction with the animals.
Each rat is assigned to only one trainer or a pair of trainers, so they get to know the animals very well. The rats become familiar with the trainers and they get attached to them, but all want their rats to pass their final test and get sent to an operational site, so they can save lives.
Rodents are the biggest order of mammals, with more than 2,000 species. Among these, APOPO selected the African giant pouched rat or Cricetomys ansorgei for landmine and TB detection. Though most rats could qualify in terms of sensitivity and intelligence, the Cricetomys has inherent advantages for the detection tasks. African giant pouched rats are: species with a very well developed olfactory capacity, they are a widespread indigenous species, adapted to the local environment, they are able to live up to eight years in captivity, they are relatively large, making them easier to work with and observe, they are calm, docile, and easy to tame and they are cheap to source, feed, breed and maintain.
The typical healthy weight range for a mature male rat is between 1075g and 1275g and for a female rat between 957g and 1157g. Their average body length is 30-40 cm, excluding the tail of 40 cm. Males are somewhat larger.
The rats have a very sensitive sense of smell. In the wild, rats can communicate over large distances using olfactory cues – and the rat’s nose is constantly active and moving. With its rather poor vision, the Cricetomys depends largely on its sense of smell. The rats can smell TNT in low concentrations and even when it’s buried under the ground (up to 15-20 cm). They can also detect the odour from a distance of about 1 meter. Apart from that, our trained rats are not distracted by other objects or odours as they specifically look for TNT/TB while ignoring other contamination.
The African giant pouched rats are sociable, clean and intelligent animals and it is very satisfying to see how they respond to our training methods and how hard they work. Many people still think of rats as dirty and stupid animals but they are actually very smart and likeable. The rats all have unique personalities. Some are very energetic, constantly moving and running about, while others are more relaxed. A few of the rats are very vocal, happily squeaking when they are about to be fed, while they are being handled, and sometimes while they are working. The different personality traits rarely prevent a rat from being trained to become a good sniffer rat, but some traits are better suited for certain types work. For example, a strong and energetic rat can usually search a large area of ground for landmines very quickly, but the rat may be more difficult to handle because it will not hold still.
So far, there are no data indicating different performances. Both male and female rats are doing an equally good job.
An important advantage of the rats is their relative independence from a personal handler. Therefore a handler does not necessarily have to follow his own animals to the demining operations. Generally, most rats remain with the same trainer, but show no significant difference in performance when taken over by somebody else in the absence of the trainer. We make sure all new handlers are briefed extensively on the specific behavior of individual animals.
All new trainers get an extensive practical training and we also conduct refresher and ongoing trainings, reviewing fundamental topics and introducing new methods and strategies. All trainers are well informed and our supervisors make sure they handle the rats correctly to avoid startling or any physical harm.