The elephants had never encountered the men who had worn the scented clothes, Byrne noted. And the clothes were kept out of sight, so smell was the only way for the elephants to detect them.
Both the Maasai and Kamba scents caused the elephants to pick up their trunks and point them towards the clothes to investigate. The animals also bunched together, a behavior that signals concern, Byrne said.
Once the elephants picked up on the nature of the scents, however, the reactions differed.
The elephants typically walked about 150 feet (46 meters) away from the Kamba scent, relaxed within a few minutes, and continued grazing.
"In the case of the Maasai scent, they would head off directly downwind, sometimes almost running, and often wouldn't stop for a kilometer [0.6 mile]," Byrne said.
"Even when they did stop, they were still bunched together, sniffing the air, and took several minutes even when they were a kilometer away to relax enough to start feeding. So it was a very strong effect."
In a second experiment the researchers exposed the elephants to a white cloth typical of garments worn by Kamba men and a red cloth like those often worn by Maasai. Neither garment had been worn.
Byrne noted that if the elephants were simply reacting to conspicuousness, the stronger reaction would have been to the bright white. But the stronger reaction was toward the red, which for elephants is a drab color.
"It was almost as if the fact that there wasn't a Maasai there—otherwise they could have smelt him—allowed them to express their real feelings, which was not very polite. They didn't like them," he said.
The researchers also expected the elephants' personal histories to evoke different individual reactions. Some have a family member that was injured or killed by spearing, for example. But they all reacted similarly.
"So we think the fear was probably socially transmitted among the elephants," Byrne said.
(Related: "Elephants 'Hear' Warnings With Their Feet, Study Confirms [February 16, 2006].)
The Human Threat
Josh Plotnik studies elephant behavior at Emory University in Atlanta, Georgia.
He was not involved in the study, which he said demonstrates that elephants are "learning how to react to the presence of man, especially when it is a threat."
He added that the findings may spur further research into using the elephant sense of smell as a way to reduce conflicts between humans and elephants. (Related: "Elephant Crop Raids Foiled by Chili Peppers, Africa Project Finds" [September 18, 2006].)
"Creating odor cues that keep elephants away might certainly be extremely helpful," he said.
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