A pilot project to turn African giant pouched rats into conservationist sleuths is literally in its infancy — the 10 to 15 rodents being reared in Tanzania to detect pungent pangolin remains as well as smuggled hardwood timber are just a few weeks old and most are still with their mothers.

The US Fish and Wildlife Service , however, is on board with the vermin trial, which organisers hope can eventually be used to find hidden elephant ivory and rhino horn. The American agency has provided $100,000 to support what it says could be "an innovative tool in combating illegal wildlife trade."

The challenge seems overwhelming.

Conservationists describe the pangolin as the world's most heavily trafficked mammal because its meat is considered a delicacy in Vietnam and some parts of China, and its scales are used in traditional Chinese medicine. Wildlife contraband is concealed among vast numbers of shipping containers that annually leave Dar es Salaam in Tanzania, Mombasa in Kenya and other African ports.

Yet APOPO , a non-profit group based in Tanzania, already harnesses the rats' keen sense of smell to find mines and other explosive material on old battlefields in Angola, Mozambique and, more recently, Cambodia. The organization also uses rats to detect tuberculosis in sputum samples of patients in Tanzania and Mozambique.

The rats in the conservation project will start "socialisation training," which means being carried around on people's shoulders and in their pockets, being driven around and generally getting used to sights and sounds, APOPO spokesman James Pursey said.

Then comes "click and reward" training in which the rats are fed a treat whenever they hear a clicking sound, and they'll eventually learn to link the gamey smell of pangolin scales with edible rewards. Later, the intensity of the pangolin smell will be reduced and other smells will be added to confuse the rats. The ultimate aim is to train the rodents to scratch or linger over the pangolin or hardwood aroma for three seconds, tipping handlers to a possible find.

APOPO is confident it can get rats to discriminate between a pangolin scent and other smells, and "the challenge is going to be how the rats actually test the containers," Pursey said.

The Endangered Wildlife Trust , a South African group leading the project, said the trial "builds on the use of scent detection by dogs, but will take advantage of the rats' added agility and ability to access the container vents, which would provide the most air from the container, and potentially the most scent. Alternatively, the rats will detect scents sampled onto a filter through the vents."

Handlers can dispatch rats with leashes and harnesses into hard-to-reach areas, but then "how are they going to tell us that they've found something?" said Kirsty Brebner of the Endangered Wildlife Trust.

One option being considered is to install small cameras on the backs of the rats, an idea that has been discussed for the detection of people trapped in collapsed buildings after an earthquake or bombing.

WWF and TRAFFIC have supported "successful" tests using dogs and air-filtering technology to detect wildlife contraband, "but we are still learning the best ways to apply the system for prime time, permanent applications," said Crawford Allan, a leader of an anti-wildlife crime initiative launched by the two conservation groups.

"Dogs do need a lot of care and we won't risk them crawling into tight spaces where they could be injured — so bringing in a conservation 'pied piper' and a squad of rats could help in those circumstances where they can move freely, with low risk in more cramped conditions inside shipping containers or on the back of trucks etc.," Allan said in an email. He is not involved in the rat research.

If the training goes well, it could still be another year or so before the rats finally get to work. They'll stick to cargo perusal rather than, for example, checking out people's luggage in airports. Travelers, Pursey of APOPO said, wouldn't be "particularly enamored" to have vermin crawling on their belongings.