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Wildlife crime is among the top illegal industries worldwide, coming in fourth after arms, drugs and human trafficking. Its value is estimated at $23 billion a year, with scales, elephant tusks and rhino horns being the most sought-after items on the black market.

But the cost far outweighs the money, as driving these species to extinction, destroying entire ecosystems and causing untold suffering to animals are just some of the far-reaching consequences that threaten the biodiversity of our planet.

The Wildlife Conservation Society reports that approximately 35,000 elephants are illegally resident poached every year. This means that every 15 minutes one elephant is killed for its ivory. Meanwhile 499 rhinos were lost illegal hunting in South Africa last year, by a staggering 51% increase compared to 2022.

To tackle the stubborn threat of poaching, which scientists have now focused on African giant possums for help, according to a study published in Frontiers in conservation science.

The research, led by Isabelle Szott, PhDa researcher at the Okeanos Foundation and one of the study’s co-authors, shows how these nocturnal creatures can detect the scent of animals and plants listed as threatened or endangered. Pangolin scales, elephant ivory, rhino horn and African blackwood are just the beginning of what these rats can learn to identify.

African giant possums rely on their sense of smell and hearing

Native to sub-Saharan Africa, African giant possums (Cricetomys gambianus), also known as Gambian possums, are the largest species of rat. They weigh up to 9 pounds and have very poor eyesight. However, to compensate for this, they rely heavily on their senses of smell and hearing.

This according to Kate Webb, PhDan assistant professor of psychiatry and behavioral sciences at Duke University and first co-author of the study, is exactly what led the research team to consider these rats when detecting poaching-related material. “Working with the Endangered Wildlife Trust (EWT) of South Africa, we have begun exploring the potential of the detection rats to combat the illegal wildlife trade,” Webb said. Interesting technology (IE) in an interview. “We believe that tackling illegal wildlife trafficking requires innovative approaches while remaining cost-effective, scalable and flexible.”

Webb, who is also a U.S. scientific advisor at APOPO, a Tanzania-based nonprofit, says the organization has been training giant rats for 25 years for scent-related tasks, including detecting landmines and tuberculosis in biospecimens. “We believed that the rats had special skills that could make them valuable members in the fight against the illegal wildlife trade,” she added. “For example, one of the main advantages of rats is that they are easily transferable between trainers.”

The neuroscientist explains how flexible rats are when it comes to betting strategies. “Rats are lightweight and small enough that they can be lifted to cover the vents at the top of shipping containers.”

The training process

The rats, named Kirsty, Marthy, Attenborough, Irwin, Betty, Teddy, Ivory, Ebony, Desmond, Thoreau and Fossey, went through several phases of training. “You might recognize some of the rats’ names,” Webb says.

“Many of them are named after interlocutors and advocates against wildlife trafficking. For example, we have David Attenborough, Steve Irwin, Dian Fossey, Betty White, Henry David Thoreau and Teddy Roosevelt!”

Webb explains how they were all trained using positive reinforcement techniques.

“During cue training, rats learn to perform a specific behavior (here in the form of holding their nose in a hole for a certain period of time) while a target odor such as pangolin scales is presented,” the neuroscientist adds. “When rats perform the so-called nose poke correctly, they are rewarded with food.”

The rats then underwent discrimination training, during which they were exposed to non-target odors such as electrical cables, coffee beans and washing powder.

These are often used to disguise the scent of wildlife in actual smuggling operations. “Here, a nose poke into a hole containing a so-called non-target does not result in a food reward, while nose pokes in wild animals are still rewarded,” says Webb. “During the discrimination phase, rats learn to identify only the odors of the wild animal targets, while ignoring non-targets.”

Teaching rats to detect wildlife requires advanced training, because traffickers are constantly coming up with new methods to hide their contraband. To increase the rats’ odor memory, the scientists exposed them to a wide range of objects. When their retention training was complete, the rats were presented with odors they had not smelled for five and eight months.

Remarkably, despite the long time difference, the rats showed perfect retention scores, indicating that their cognitive retention ability is comparable to that of dogs. In addition, eight of them successfully identified four commonly traded animal species from a list of 146 non-target substances.

“These rats performed exceptionally well when presented with this challenge, detecting wildlife targets and ignoring nearly 150 non-target items, including biologically relevant odors such as the scent of another rat or palatable food items such as peanuts,” says Webb.

“I wasn’t necessarily surprised that they could perform so well, but our findings only highlighted what incredible senses of smell these rats possess!”

When asked about the welfare and ethical treatment of the rats, Webb assures that each rat is well cared for, given a nutritious diet, regular exercise, mental stimulation, enrichment and loving attention from their expert handlers.

“Each of our rats is considered a highly valuable asset, making animal welfare a top priority,” Webb explains. “If a rat decides to stop working, or if its performance declines, or if it suffers from age-related health problems, it retires.”

Practical applications and further steps

The next phase, Webb explains, involves preparing the rats to work in ports. They will be equipped with specially designed vests, each with a small ball attached to it.

When the rats use their front paws to pull the ball, the vest emits a beeping sound, alerting their handlers to the detection of a target. “We see rats as an additional and complementary tool to combat the illegal wildlife trade,” Webb said. “They are cost-effective, which makes them an attractive option, especially in developing countries.”

The neuroscientist emphasizes that rats can also be used to shield areas in shipping ports that dogs cannot reach, such as ventilation openings on containers. “The more pressure we can put on smuggling networks, the greater the cost to their operation,” Webb added. “Developing new and innovative methods to combat the illegal wildlife trade is a signal to poachers and smugglers that we are committed and steadfast in our fight against all forms of illegal trade.”

After several successful trials in port environments, the researchers are confident that further operations will require the support of every country to not only import the rats, but also deploy them and recognize their findings as evidence.

As for whether African giant possums could potentially be used for other detection capabilities, such as human and drug trafficking, Webb is confident they can be trained to identify a wide range of substances.

“We believe the rats have the potential to support more efficient, cost-effective screening and serve as an additional deterrent,” Webb concluded. “Wildlife smuggling is often carried out by individuals engaged in other illegal activities, including human, drug and arms trafficking. That is why using rats to combat wildlife trafficking can contribute to the global fight against networks that exploit people and nature.”