Rats trained to sniff out smuggled rhino horn and pangolin scales

This story was originally published by The Guardian and appears here as part of the Climate Desk collaboration.

Rats could be the latest weapon deployed in the fight against endangered wildlife trafficking, according to a study of rodents trained to sniff out pangolin scales, rhino horns, elephant tusks and hardwood.

Researchers trained eight African giant pouched rats to sniff out the contraband, even when it was hidden among items commonly used to hide trafficked goods, including peanuts, leaves, wigs and washing powder.

The market for illegal wildlife products is worth up to $20bn (£15.5bn) annually, Interpol said last year.

The rats were studied by scientists at Apopo, a Belgian-founded, Tanzania-based NGO, whose rodents also sniff out landmines and tuberculosis.

Named after conservationists including David Attenborough, the animals were initially rewarded with a food pellet if they held their nose for three seconds over a sample of pangolin scale, wood, rhino horn or elephant ivory.

In simulations, they were dressed in tiny red vests attached to leashes, with a beeper attached to the front so they could use their front paws to alert their handlers when they found contraband – for which they would receive another reward of food.

The rats were able to perfectly detect pangolin, wood and rhino horn after eight months of not smelling them, according to Apopo’s study, which was published in the journal Frontiers in Conservation Science. The researchers said this suggested that rats could remember smells for as long as sniffer dogs.

But, they said, their results for elephant ivory may not be accurate, as that had been stored with the rhino horn and rats trained only on rhino horn sniffed it out.

In 2023, the rats were also put to the test in a real-world simulation in the port of Dar es Salaam, Tanzania’s commercial capital. The rats found 85% of planted illegal wildlife samples, Apopo said, even through vents in shipping containers.