Researchers have trained African giant pouched rats to sniff out tuberculosis and explosives in the past. And they have now expanded the rodents’ scent repertoire to detect illegally trafficked animal parts — including pangolin scales, elephant ivory, and rhino horn, according to a report in Frontiers in Conservation Science.
Interrupting this illegal trade is important in and of itself, of course. But the people who smuggle animal parts often also traffic drugs, humans, and weapons. But why rats?
Rats as Detection Tools
They have a great sense of smell, learn easily, and live long. Unlike dogs, they can work with multiple handlers.
“That gives them a bit of an advantage over scent detection dogs,” says Kate Webb, an assistant professor at Duke University Medical Center and an author of the study. Then there’s cost. The typical detection rat requires about nine months to train, costing $6,000 to $8,000. Training a scent detection dogs costs $10,000 to $30,000.
“We think of the rats as a pretty cost-effective detection tool,” says Webb.
Size is also a factor. Unlike dogs, rats can wriggle through the cracks and crevasses of a container ship. They can be lifted high to sniff air vents.
But perhaps most importantly, they are excellent at their jobs. After training, “proof of principal” studies reported in this paper showed just how good. The eight rats could identify four commonly smuggled wildlife species among 146 non-target substances — some of which — like coffee — are often used to mask the scent of contraband.
The rats also have great scent memory. They could recall smells they were trained to detect months after their last exposure.
Read More: Working Detection Dogs Help Conservation Researchers Sniff Out Data
Training the Rats
Since the “proof of concept” training and testing, the researchers have tried them out in a real-world setting—the Dar es Salaam seaport in Tanzania.
“The rats have performed very well both times,” says Webb.
During these more practical trials, the researchers experimented with search strategies. Some rodents were led by leash. Others were lifted by elevator-like devises to access hard-to-reach places. Some rats even learned to press a switch that activates a beeping sound when they found a target.
The rats – Kirsty, Marty, Attenborough, Irwin, Betty, Teddy, Ivory, Ebony, Desmond, Thoreau, and Fossey — went through several training stages. First, they learned to hold their noses in a hole where the target scent was placed. Next, they were rewarded when they poked their nose into a hole with the scent versus ones without. Then they were exposed to many non-target scents — often things used to mask the smell of illegally trafficked wildlife.
Finally, after five and eight months away from the scents they were trained to protect, they were tested again. Even after those smell-free months, the rats demonstrated scent retention as good as trained dogs.
Read More: The History of the Lab Rat
Expanding the Scent Repertoire
Next steps include experimenting with different ways to detect a wider variety of scents in a multitude of environments. Since the animals are small and relatively inexpensive, Webb envisions a small rat patrol being deployed in airports and harbors. Each rat could have its own scent specialty. Some could pursue narcotics, others could go after illicit animal parts.
One of the biggest training challenges? Teaching humans not to recoil from the rodents, which Webb says have unfairly attracted a bad rap. People are used to encountering scent dogs in airports. Rats? Not so much.
A marketing effort may be necessary to change minds. “Our rats, in my opinion are incredibly cute,” says Webb. “They have personalities. They live for a long time. You get very attached to them. And they’re doing great and important work.”
Read More: These 6 Animals Are Attracted to Weird Scents
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Before joining Discover Magazine, Paul spent over 20 years as a science journalist, specializing in U.S. life science policy and global scientific career issues. He began his career in newspapers, but switched to scientific magazines. His work has appeared in publications including Science News, Science, Nature, and Scientific American.
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