'Smell That?', One Elephant Asked Another

Sure, a mouse can smell a cat, and a vervet monkey can smell an approaching leopard, and lots of animals can smell the most dangerous hunter of all—man. But here’s a new one: elephants that can tell members of one African tribe from another by smell.

It’s a useful skill. In the Amboseli region of Kenya, the cattle-herding Maasai warriors show off their virility by spearing elephants (not fatally, in many cases), while the agricultural Kamba leave the elephants alone. Telling Maasai from Kamba seems like a good way to avoid danger, if you're an elephant, so scientists tested 18 groups of pachyderms in Amboseli to see what they were capable of.

In the experiment, being reported today online in the journal Current Biology, the scientists left out three kinds of garments: cloths that had been worn for five days by an adult Masai man, cloths that had been worn for five days by a Kamba man, and clean unworn cloths. Then they measured how the elephants reacted--how long they froze after catching the scent of the garment (it was obvious when an elephant smelled the cloth: he paused, raised his head, and curled his trunk upward in the direction of the scent), how fast they ran way in the first minute of flight, how far away they moved in the first five minutes, and how long it took them to relax.

“We expected that elephants might be able to distinguish among different human groups according to the level of risk that each presents to them, and we were not disappointed,” said Richard Byrne of the University of St. Andrews, who led the study.

The scent of a garment worn by a Maasai man made the elephants flee twice as fast as when they smelled never-worn clothing or clothing worn by a Kamba man. They traveled some four times as far. They also took twice as long to relax. The Maasai cloths also made the elephants flee to taller grass than the Kamba cloths did. The elephants were reacting to smell alone, since the cloths were never closer than 30 feet to them too far to see. “Elephants can classify members of a potential predator species into subgroups based on [smell] alone,” conclude the scientists.

The basis for the difference in smell is probably the different diets of the Kamba and Maasai. The latter, since they raise cattle, consume significant amounts of milk, cattle blood and meat, while the Kamba diet is mostly maize, vegetables and meat, differences that can translate into different body odors. Also, the scent of cattle permeates Maasai villages, and the warriors smear themselves with sheep fat and ochre as decoration.

Curiously, whether or not an elephant group had ever had a member speared by a Maasai warrior had virtually no effect on its reaction to the Maasai odor. The groups’ reactions “did not differ with their spearing history,” write the scientists. “Reactions were strong, even in groups with the least experience of spearing.” That suggests a remarkable learning curve, as one group of elephants with experience of bloody encounters with the Maasai somehow conveys to elephants with no such history that a particular smell means trouble.