Chishuru, a large African elephant bull with a talent for sniffing out TNT, stood in front of a line of seven white buckets.
Inside one of the buckets on a recent morning was a slight trace of TNT on a piece of paper stapled to the bottom. Chishuru's job was to find out exactly which bucket it was—using his nimble trunk to guide the way.
The elephant ambled between the buckets, snaking his long trunk into each one—there were different, harmless scent traces in each bucket—and taking a big sniff before moving on to the next. At the fifth bucket he paused and raised his right leg, indicating to a research team that this was the one with a trace of TNT inside. Bingo.
The pachyderm is among a group of tame African elephants helping the U.S. military develop an artificial "nose" that could safely and effectively detect bombs and other explosive devices, officials say.
The U.S. Army Research Office experiments, which take place at the Adventures with Elephants ranch here, are part of an effort to better understand—and eventually reproduce—elephants’ stellar sense of smell.
The objective, says Stephen Lee of the U.S. Army Research Office, is not to put elephants in the field of combat or use them for mine detection.
“We are trying to understand how elephants smell with their trunk," Lee says, "and how sensitive they are to specific odors."
Elephants have a keener sense of smell than dogs do, Lee says, and he and his teams are working to determine how much sharper their sniffer is when it comes to locating TNT. Currently, military working dogs are used for either explosives or narcotics detection, primarily by military police.
"The data show that elephants have an amazing capacity for TNT detection," says Ashadee Kay Miller, a scientist at South Africa's University of Witwatersrand who works with the ranch. She emphasizes that the military will not put elephants into combat or use them to directly detect explosives.
During the two-year Army project, "they've never missed a sample in the second phase of testing, which is an improvement on the TNT-detection dogs working under similar conditions," says Miller, who is writing a scientific paper about the elephants’ ability to detect TNT using smell, and how their abilities compare to those of dogs.
Technology inspired by the elephant's sense of smell could be a vast improvement over the military's current handheld electronic sensors that detect explosives, Lee says.
Using a handheld sensor can be dangerous, because it has to be placed very close to the explosive's odor to work effectively.
Elephants, on the other hand, can detect odors from a distance—an ability that could help lead to a much safer technology. The research teams are trying to determine how close an elephant needs to be to pick up the scent of TNT, but wild elephants have been known to smell people, depending on the wind direction, from more than a kilometer (0.6 mile) away.
Their sense of smell is targeted, and research has shown that they don't need to go to different locations to home in on an odor, as would a domestic dog.
Beyond developing better electronic sensors, the military could also collect soil or air samples by flying drones over suspected minefields and send the samples to trained elephants for testing.
"For relying on biodetectors to find potential lethal weapons like bombs,” Miller said, "my money is on the elephant."
The Ultimate Sniffers
Elephants have 2,000 genes for smell, the most of any animal on Earth—more than twice those of the domestic dog and five times more than those of humans, according to a 2014 study in the journal Genome Research.
A previous study in Kenya found that elephants can distinguish which tribe a person belongs to by their smell, and will actively avoid those from tribes that have been hostile toward them.
And in postwar Angola, elephants have been observed avoiding landmine fields, possibly because they can smell the mines underground.
At the Adventures with Elephants ranch, a safari business about 100 miles (160 kilometers) from Pretoria, owner Sean Hensman knows how smart and skillful the giant mammals can be.
"We are only scratching the surface of what we know about this animal," says Hensman.
"Their intelligence, scent, and communication abilities—it's really exciting." (See National Geographic’s elephant pictures.)
Hensman's family began working with elephants in Zimbabwe in 1988, when Sean Hensman's father, Rory Hensman, acquired a group of elephants that had been earmarked for culling, relocated them to his farm, and later started up the first elephant-back safari business in Zimbabwe. In 2002, during the Zimbabwean land reforms—an effort to redistribute land among black farmers—the Hensmans were forcibly removed from their farm.
In 2014, the family established the Rory Hensman Elephant Research Institute, which works with scientists on issues such as acoustic communication, scent recognition, and population management to better understand the species and to assist with resolving human-elephant conflict across Africa.
Though the TNT-sniffing elephants won't be put on the front lines, Joyce Poole, an expert in elephant behavior and co-founder of the conservation group ElephantVoices, is wary of any research that involves captive elephants.
"Elephants do have an amazing sense of smell, and it is possible that orphan elephants raised with kindness might be able to do some extraordinary work for humans," says Poole, a National Geographic explorer. (Also see "Ringling Bros. to Retire Its Circus Elephants.")
But, she cautions, people working with the animals need to be careful not to unknowingly harm them.
Hensman insists that his elephants—all of which were either earmarked for culling or were going to be shot as "problem animals"—are happy at his farm, where they spend their days roaming a 7,400-acre (3,000-hectare) area, interacting with tourists and working with researchers who visit the farm.
And the U.S. Army's Lee argues that using elephants for research could actually help their wild brethren.
"A better understanding of elephants can help alleviate conflict in areas where there is human pressure on the animals," he says.
In highly populated areas, elephants can be dangerous, and encounters between the animals and people have increased as more people move into elephant habitat.
More than 200 people were killed by elephants in Kenya over the past seven years, according to the conservation group WWF, and sometimes people will kill the animals in retaliation.
Instead of clashing with people, Chishuru, the star sniffer bull, now represents the enormous potential of what we can learn from elephants. And he may inspire the next generation of artificial noses that could save lives—on the battlefield and beyond.
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