Gorillas are intelligent apes, communicating with each other through a variety of signals. Now, scientists may have just uncovered another method for silverback gorillas to communicate; they've found that the apes use odor as a way to make their messages clear.

Mammals can communicate socially through visual, auditory and chemical signals. The chemical sense, though, is probably the oldest sense and is shared by all organisms, including bacteria. Despite it being one of the oldest senses, though, researchers know very little about it when it comes to apes.

That's why researchers decided to take a closer look. They analyzed odor strength in relation to arousal levels in a wild group of western lowland gorillas in the Central African Republic. They specifically focused on the male silverback, which was the mature leader of the group. They also determined the factors that predicted extreme levels of odor emission from the silverback.

In the end, the researchers found that the male silverback may actually use odor was a modifiable form of social communication. Context-specific chemical-signals may moderate the social behaviors of other gorillas. This form of communication between apes could be especially useful in Central African forests, where limited visibility may necessitate reliance on other senses.

"No study has yet investigated the presence and extent to which chemo-communication may moderate behavior in non-human great apes," said Michelle Klailova, one of the researchers, in a news release. "We provide crucial ancestral links to human chemo-signaling, bridge the gap between Old World monkey and human chemo-communication, and offer compelling evidence that olfactory communication in hominoids is more important than traditionally thought."

The findings reveal how visual and vocal communications aren't the only forms that mammals use. By using chemical communication, these apes can utilize an older sense in order to transmit cues through dense forests.

The findings are published in the journal PLOS One.