Sniffers

Dolittle’s Raiders
Fortune; May 2, 2005

BYLINE: David Stipp


There’s a rat loose here- at the Downstate Medical Center in Brooklyn, N.Y., and it's coming right at me. Suddenly it veers and goes back the way it came. Then it loops around and darts toward me again. It seems to be one dizzy rodent. But it's not. Its movements are being directed by a higher power--I'm playing with its mind by remote control.

Rat No. 3, as she's known, is wearing a tiny backpack crammed with electronics from which several wires lead into her brain through a plastic cap on her head. When I press a personal computer's cursor-control keys, radio signals are transmitted to the backpack, which in turn sends electrical impulses to the parts of her brain that register sensory input from her whiskers. Neuroscientist John Chapin and colleagues here have taught her to go left when her brain's left-whisker area is stimulated, and right upon a right-side tweak. Their training method resembles teaching a dog to roll over: When No. 3 moves as directed, they stimulate her brain's "reward" center through a third wire--like giving a treat to Rover.

The most important thing she's learning is that explosives have yummy aromas. More on that process later. But first the why: "Roborats" like No. 3 may someday be the terrorist's worst nightmare--keen, furtive little spies that can be guided into a building through, say, an air duct and then allowed to roam freely to sniff out explosives, toxic chemicals, or other bad stuff. The team at the Brooklyn center, part of the State University of New York, has even mounted tiny cameras on roborats' backs, enabling remote handlers to see where their furry operatives are going--and what they're finding.

You don't have to think very far out of the box to grasp the attractions of small, cheap, fast-reproducing animals as bomb sniffers. In recent years the Department of Defense has sought to enlist a number of nosy little creatures for the perilous job, including rats, wasps, honeybees, and even yeast (yes, yeast). The program is still a work in progress. But it has shown in fascinating detail that dogs are not the only Einsteins of olfaction, nor necessarily the best animals for nosing out explosives.

Unlike dogs, small animals can walk (or fly) over land mines without setting them off. Bees don't get hip dysplasia. Sniffer dogs need frequent rests; wasps don't. And it's a lot easier to come by insects and rodents than the purebred dogs preferred by bomb squads. In fact the market for sniffer dogs has gotten so hot since 9/11 that con artists have moved in: In 2003 the owner of a Virginia kennel was convicted of fraud after he charged federal agencies more than $ 700,000 for a pack of clueless pooches. In one test they allegedly failed to detect a huge cache of explosives hidden in vehicles right in front of their schnozzes. Bad dogs.

Most of the studies on non-dog sniffers have been funded by the U.S. Defense Advanced Research Projects Agency, or DARPA, an elite force permanently deployed on the border between science and science fiction. A few years ago, says Alan Rudolph, who formerly oversaw DARPA's sniffer-critter projects, it occurred to agency scientists that species whose survival has depended for millions of years on the ability to scent mates and food should have olfactory senses at least as keen as dogs'. Soon after, Rudolph, now CEO of Adlyfe, a Rockville, Md., biotech, began enlisting animal-olfaction experts to see if their favorite beasts could be taught to associate the aroma of explosives with things to which they're attracted.

Forming such associations is obviously a piece of cake (or madeleine) for higher mammals from Lassie to Marcel Proust. But can rats and bugs even smell stuff like TNT, much less be taught to follow their noses to it?

W. Joe Lewis, a Department of Agriculture scientist in Tifton, Ga., was asked by DARPA to answer this question about parasitic wasps. The housefly-sized insects are known for using needle-sharp ovipositors to implant their eggs in caterpillars; the wasp larvae hatch and devour the hosts' insides before bursting out like the vicious beasties in Alien. Lewis's group earlier discovered that wasps exposed to a particular odor while doing their favorite things (stabbing caterpillars or sipping sugar water) would later gravitate toward the odor when re-exposed to it. Significantly, the wasps could be taught to be attracted to very faint odors they don't encounter in the wild.

Getting wind of the findings, DARPA "asked us if we could use wasps like dogs," says Lewis. "At first the idea was to train them to hover over someone [smelling of explosives] like a cloud of mosquitoes." That gave way to a better idea: With colleagues Glen Rains and Jim Tumlinson, Lewis devised a handheld container with a hole through which outside odors are wafted. Inside, wasps previously taught to love the odor of an explosive are monitored with a tiny camera linked to a computer. The system registers when the insects cluster near the hole, showing they've gotten a whiff of bomb stuff. Now the team is seeking backers to commercialize the work.

Meanwhile, DARPA-funded University of Montana researchers have taught honeybees to associate the odor of explosives with sugar water. Led by entomologist Jerry Bromenshenk, the group has devised a clever way to use the trained insects as land-mine finders: The scientists turn the bees loose, then use a radar-like system that bounces laser light off them to show where they tend to cluster. The team was able to locate several defused land mines at a U.S. Army test site, according to a 2003 report. The real-world potential isn't clear, though--flowers might distract the bees, for instance. (DARPA declined to comment on the status of its sniffer projects.)

Perhaps the most futuristic sniffers on the agency's list are yeast. DARPA grantee Atto Bioscience, a Rockville, Md., biotech acquired last year by Becton Dickinson, has installed genes for mammalian olfactory receptors in the one-celled microbes. (The receptors are molecules jutting from nose cells that glom onto airborne chemicals, triggering nerve signals.) With additional gene implants, the Rockville team hopes to get the altered yeast cells to light up like tiny fireflies when they "smell" explosives. "We've achieved partial success," says team leader Michael Brasch. But the microbes won't nose out dogs anytime soon.

Rats, on the other hand, could soon pose some sniff competition. African giant pouched rats, which resemble big-eared cartoon rodents the size of rabbits, are leading the way. They're being trained to sniff out land mines by a Belgian nonprofit group called Apopo, which plans to put them to work this year in Sudan.

Professor Chapin of the Brooklyn roborats recently devised an elegant solution to a longstanding problem: determining when a sniffer rat has found a bomb. That's not easy with an animal roving far from its handlers. His idea is simply to add a button to roborats' backpacks; the animals would be trained to press it when they smell a bomb, transmitting a signal to home base. That is brilliant: Rats readily learn to press levers for rewards, and Chapin's team has already taught roborats to sniff out objects redolent of plastic explosives. Still, he isn't certain it will work--the rats may learn to push the buttons for rewards when there's no bomb around. That's just what you'd expect of a dog surrogate: an animal that plays with our minds.

Copyright 2005 Time Inc.