how I train rats to sniff out explosives

“My job is to train rats to detect landmines so the explosives can be cleared to save lives. I work for a Belgian non-governmental organization called Apopo that operates from Morogoro, in my home country of Tanzania. The rats I train are used in mine-clearing programmes around the world, including in Angola, Azerbaijan and Cambodia.

I trained Ranen, the rat I’m holding in this picture. The animals we use are African giant pouched rats (Cricetomys gambianus). They are indigenous to sub-Saharan Africa and are the size of a small cat, which makes them easy to handle. They also live longer than other rats, which is helpful for the programme, because it takes between nine months and a year to train one fully.

My colleagues and I use a method called clicker training: we teach the rats to associate a click with a food reward, and then use clicks to progressively reward behaviour. Rats are naturally curious, so they will explore, and their great sense of smell means they can detect buried explosives.

To teach the rats what to look for, we place small amounts of TNT explosive in tea-eggs: the small metal containers normally used to brew loose-leaf tea. We reward the rats for touching these, then move on to reward them only when they touch a tea-egg filled with explosives, rather than ones filled with distractions, such as hair, flowers or herbs. The rats need to perform perfectly at each stage of training before they progress. In the final stage, we use real deactivated landmines in a training field.

As trainers, we build a connection with the rats we train. Some are slow learners; others grasp the concepts very quickly. Most of the rats make it through, eventually. I work with our resident scientist to continually monitor and tweak our training programme, because the rats are so clever that they can outsmart the trainers!”

This interview has been edited for length and clarity.