African Rats Detect Scent and Combat Wildlife Trafficking

Researchers train giant African pouched rats to sniff out illegal wildlife.

Reviewed by Lybi Ma

Key points

• Researchers trained African giant pouched rats to detect the scents of illegally trafficked wildlife.
• Rats could identify pangolin, ivory and other wildlife products even when concealed among other substances.
• Rats also remembered scents they were trained on after delays of several months.
• Future work will test the rats’ ability to search in seaports and airports with a lot of wildlife trafficking.

The scale of the illegal wildlife trade is enormous and threatens many animal and plant species. Around the world, international ports need more resources to screen shipping containers for smuggled wildlife. According to new research, help could arrive soon—in the form of trained rats. A proof-of-principle study shows that African giant pouched rats can successfully learn to detect the scents of pangolin scales, elephant ivory, and other illegal wildlife products.

The research was conducted at APOPO, a Tanzania-based, non-profit organization. Since the 1990s, APOPO has worked with African giant pouched rats to provide low-tech, cost-efficient solutions to global humanitarian crises. Today, some of APOPO’s rats sniff out landmines, while others are trained to detect tuberculosis.

For the new study, researchers examined whether these rats could fill a gap in combating the illegal wildlife trade. Current screening tools, like X-ray scanners and scent detection dogs, are expensive, time-intensive, and thinly stretched.

“My first answer to ‘Why African giant pouched rats?’ is that they’re very cute,” says Isabelle Szott of the Okeanos Foundation, one of the study’s authors. She also cites the rats’ excellent sense of smell, long lifespan, and low training and maintenance costs. “Some advantages of rats are their cost-effectiveness and small size,” says Szott. “We can screen areas that dogs might not be able to reach because we can easily lift the rats up high.”

Crime-Sniffing Rats

APOPO is headquartered in Tanzania, a country that sees a lot of wildlife seizures at the seaport of Dar es Salaam. “The seizure reports often include pangolin, which is the world's most trafficked animal, as well as elephant ivory, rhino horn, and hardwood timber,” says Kate Webb of Duke University, one of the study’s authors.

Szott, Webb, and colleagues worked with the Tanzanian government and the Endangered Wildlife Trust to procure specimens to train the rats—who were named after conservationists and advocates against the illegal wildlife trade, including the Irwin family, Betty White, and David Attenborough.

First, the rats learned to hold their noses for several seconds in a hole if they detected pangolin scales, rhino horn, elephant ivory, or African hardwood. Then the researchers introduced non-target odors, like electric cables, coffee beans, and washing powder. Smugglers use these to mask the scent of illegal wildlife. By the end of training, eight rats could pick out the four target scents among 146 non-target substances. The rats could also remember the smells they were trained on even after not encountering them for several months.

“We set out to determine if the rats can detect these targets and they absolutely can,” says Webb. “As soon as we analyzed the data from this proof-of-principle, we were excited and ready to move into the next testing phase.”

The next step was preparing the rats to detect these scents in a real-world environment, like a seaport. That involved putting the rats in custom-made vests, each fitted with a small ball at the front. The rats were trained to use their paws to pull the ball, emitting a beeping sound to alert their handler that they detected a target.

The rats have now finished two sets of trials at the seaport, and their success has surpassed Szott’s expectations. “From day one, they were doing their job,” she says. “Forklifts were driving past and massive machines moving shipping containers around, and the rats were completely unfazed.”

Next, the rats will be tested at the Dar es Salaam airport in Tanzania. It will require a different search strategy, which may challenge the rats, says Webb. “We want to make sure we can show that the rats can be reliable in different settings when we’re having conversations with governmental agencies interested in having the rats deployed operationally,” she says.

A Role for Rats

The researchers say scent-detection rats could be a valuable, additional tool in fighting wildlife trafficking. Rats won’t replace other screening methods, though they may free up existing tools for other purposes, according to Szott.

“Detection dogs are amazing at tracking,” she says. “You can have a dog track poachers through the Serengeti; you’re not going to have a rat do that.”

But Szott is convinced that rats can detect smuggled wildlife. “It’s up to us to create the environment in which we allow them to be deployed and up to governments to create the legal system to allow their findings to be admitted in court as evidence,” she says.

Szott and Webb acknowledge that the public image of rats could use some help. APOPO is working hard to promote a positive image of their rats, with ambassador animals to spread the message and a visitor center where you can watch the rats in action. People can also symbolically adopt a rat to support APOPO’s work. Adopters receive updates on “their” mine detection rat or tuberculosis detection rat.

“I think that when you first tell this story, there's that initial surprise,” says Webb. “There might be some skepticism. And that's why we should use rigorous methods. We tested it in a controlled environment, that adds to the trust of using these rats in an operational setting.”

When it comes to the potential of African giant pouched rats, “the sky’s the limit,” according to Szott. “We just have to invent the methods that allow them to perform. But so far, I don’t think there’s been anything that APOPO has thrown at these rats that they haven’t been able to do.”