When it comes to wild ape communication, it's not just monkey see, monkey do — it's also monkey smell, monkey do. A new study finds that gorillas use odor signals to communicate. The study — the first analysis of chemical signaling in wild gorillas — may also shed light on how odor signalling between humans evolved.
The study originated when researchers studying western lowland gorillas in the Central African Republic noticed that the leader of the group emitted particularly strong odors in certain situations. They knew from other studies that human odors can help us identify each other or pick up on someone's mood or even their status. The silverback's behavior made them wonder whether the apes might also use odor to communicate. To find out, the scientists tracked the 13-member Makumba group, named after their leader, for one year, monitoring Makumba's odor and behavior as well as those of the other members of the group. The researchers found that he was, indeed, using odor as a form of communication, sending out strong "back off" odor signals when in the presence of other groups or rival males, and emitting milder ones when several group members were close by, most likely to help them keep tabs on his whereabouts. "As interaction intensity increased, the emission of extreme odors significantly increased," the researchers wrote.
Importance of Odors
But Makumba only emitted extreme odors when also making "visual threat displays" or grunting loudly, the researchers discovered — not when he reacted quietly during conflicts. (When tension mounted with other groups, Makumba reacted in one of two ways: He either became quiet and backed down, or he became aggressive.) But there was a whiff of weaker scents during those quiet responses to conflict, which may be a signal of reassurance to the group. "Results suggest that silverbacks may use context specific chemo-signals to moderate the social behaviors of other gorillas," the authors conclude. The study, published today in the open-access journal PLOS ONE, suggests that odor signals may be especially useful in central African forests, where visibility is limited. What's more, the findings provide evidence for how human olfactory communication may have evolved. The study offers compelling evidence that odor communication in apes "is much more important than traditionally thought," said Michelle Klailova, the study's lead author, in a statement.
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