Mammals communicate socially through visual, auditory, and chemical signals. The chemical sense is in fact the oldest sense, shared by all organisms including bacteria, and mounting evidence suggests that humans also participate in social chemical signalling.
However, not much is known about this type of signalling in closely related hominoids, like wild apes.
To better understand chemical communication in apes, Michelle Klailova from University of Stirling, UK, and colleagues analysed odour strength in relation to arousal levels in a wild group of western lowland gorillas in the Central African Republic.
Scientists determined the factors that predicted extreme levels of odour emission from the silverback.
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They hypothesised that if gorilla scent were being used as a social signal, instead of only a sign of arousal or stress, odour emission would depend on social context and would vary depending on the gorilla's relationship to other gorillas.
According to the results, the male silverback may use odour as a modifiable form of social communication, where context-specific chemical-signals may moderate the social behaviours of other gorillas.
The authors predicted extreme silverback odour, where the odour was the only element that could be smelled in the surrounding air, by the presence and intensity of interactions between different gorilla groups such as silverback anger, distress and long-calling auditory rates, and the absence of close proximity between the silverback and the mother of the youngest infant.
"No study has yet investigated the presence and extent to which chemo-communication may moderate behaviour in non-human great apes," Klailova said.
"We provide crucial ancestral links to human chemo-signalling, bridge the gap between Old World monkey and human chemo-communication, and offer compelling evidence that olfactory communication in hominoids is much more important than traditionally thought," he added.
The study is published in the journal PLOS ONE.