Officials working to combat wildlife smugglers may have a new, furry tool to help sniff out illegally trafficked items: giant rats with tiny backpacks.
A study published in Frontiers in Conservation Science indicates that the African giant pouched rats, with their keen sense of smell, can successfully sniff out parts of endangered animals and remember the scent months after training. Employing them in the field could increase pressure on wildlife smugglers and add a flexibly deployable tool to screen cargo, the researchers said.
"Our study shows that we can train African giant pouched rats to detect illegally trafficked wildlife, even when it has been concealed among other substances," Dr. Isabelle Szott, a researcher at the Okeanos Foundation and first co-author of the study, said in a statement.
"The rats also continued to detect the wildlife targets after not encountering that species for a long period," added first co-author Dr. Kate Webb, an assistant professor at Duke University.
In the past, African giant pouched rats have learned to detect explosives and the tuberculosis-causing pathogen. Now, researchers have trained these rats to pick up the scent of pangolin scales, elephant ivory, rhino horn and African blackwood -- all of which are listed as threatened and at high danger of extinction.
"Existing screening tools are expensive and time intensive and there is an urgent need to increase cargo screening," said Szott. "Rats are cost-efficient scent detection tools. They can easily access tight spaces like cargo in packed shipping containers or be lifted up high to screen the ventilation systems of sealed containers."
For the study, a team of 11 rats underwent several training stages. During indication training, the rats learned to hold their noses for several seconds in a hole in which the target scent was placed. When they correctly performed this "nose poke" they were rewarded with flavored rodent pellets.
In the next step, the rats were introduced to non-target odors. These included electric cables, coffee beans, and washing powder – objects that are frequently used to mask the scent of wildlife in real-life trafficking operations.
"During the discrimination stage, rats learn to only signal the odors of the wildlife targets, while ignoring non-targets," Szott said.
The rats were also trained to remember smells. At the end of their retention training, they were re-introduced to scents they had not encountered for five and eight months. Despite months of non-exposure, the rats showed perfect retention scores, suggesting that their cognitive retention performance resembles that of dogs.
By the end of the training, eight rats were able to identify four commonly smuggled wildlife species among 146 non-target substances.
The next step, the scientists said, is to develop ways for the rats to work within ports through which smuggled wildlife is trafficked. For this purpose, the rats will be outfitted with custom-made vests. With their front paws, they can pull a small ball attached to the vest, which emits a beeping sound to alert their handlers when they detect a target.
"The vests are a great example of developing hardware that could be useful across different settings and tasks, including at a shipping port to detect smuggled wildlife," said Webb.
While the study demonstrates that rats can successfully identify trafficked wildlife, researchers noted that it also comes with limitations. For instance, the study was conducted in a controlled environment, which is not reflective of the settings in which wildlife is commonly trafficked or screened by scent-detection animals. To deploy rats for this task, new methods need to be developed, the researchers pointed out.
"Wildlife smuggling is often conducted by individuals engaged in other illegal activities, including human, drug, and arms trafficking. Therefore, deploying rats to combat wildlife trafficking may assist with the global fight against networks that exploit humans and nature," Webb said.