Macaques are a diverse genus of Old World monkeys found across Asia and Africa. They are known for their complex social structures and cognitive abilities. In their societies, macaques use a well-developed communication system to navigate relationships. A significant component of this system is non-verbal, relying on a repertoire of facial expressions to convey information and intent.
The Social Importance of Facial Cues
Facial expressions are important for the stability and structure of macaque social life. They serve as rapid signals that help maintain the group’s hierarchy, where each individual knows its place. Through specific facial cues, a macaque can signal dominance to assert its rank or display submission to a higher-ranking member, effectively preventing a physical confrontation.
The use of facial signals also reinforces the social bonds that hold the troop together. Gestures can be used to request participation in friendly activities like grooming or to signal peaceful intentions during an approach. The ability to correctly interpret these facial cues is a necessary skill for every member of the troop, influencing everything from access to food to mating opportunities.
Common Macaque Expressions and Interpretations
Macaques use a wide array of facial expressions to communicate social information. One of the most common is lip-smacking, which involves a rapid opening and closing of the mouth. This is an affiliative signal, often used as a friendly greeting or to show peaceful intentions, particularly when a lower-ranking macaque approaches a more dominant one. It is also observed during grooming sessions, helping to strengthen social bonds.
Another expression is the bared-teeth grimace, where both the upper and lower teeth are exposed by retracting the lips. Though it may resemble a human smile, its meaning is entirely different. This expression is a sign of submission, fear, or stress. A subordinate macaque will display a fear grimace toward a dominant individual to appease it and avoid aggression.
A direct stare combined with raised eyebrows constitutes a clear threat display. This expression is used by dominant individuals to intimidate subordinates and assert their rank without resorting to physical violence. The intense gaze signals aggressive intent and serves as a warning to the other macaque to back down.
Yawning can also function as a form of communication, though its meaning can vary with context. In some situations, it can be a sign of tension or social stress. However, when directed at a rival, a yawn that prominently displays the macaque’s long canine teeth can act as a powerful threat. This gesture serves to remind the other animal of the potential for injury.
A more subtle expression is the pursed-lip face, where the lips are compressed and pushed forward. This gesture can indicate anxiety or serve as an appeasement signal toward a dominant animal. In some species, it is also used by females to solicit the aid of a high-ranking male against an opponent. In contrast, a relaxed, open-mouthed expression is often seen during social play among young macaques, signaling that the accompanying behavior is not serious.
Misinterpreting Macaque Signals
Humans unfamiliar with macaque behavior often make errors in interpreting their facial expressions, which can lead to negative outcomes. The most common mistake is perceiving the bared-teeth grimace as a friendly “smile.” Believing the animal is happy and receptive, a person might move closer to offer food or take a picture.
This action is perceived very differently by the macaque. The animal, which is already feeling fearful or stressed, interprets the human’s advance as an escalation of a potential threat. Because its signal of submission has been ignored, the macaque may feel cornered and resort to aggression as a form of self-defense. This can result in bites or scratches.
Beyond the Face: Body Language and Vocalizations
While facial expressions are a component of macaque communication, they do not occur in isolation. The meaning of a facial cue is often clarified or modified by accompanying body postures and vocalizations. This multi-modal system provides a richer stream of social information, reducing misinterpretation within the group.
Body language provides context. A dominant macaque delivering a threatening stare may also stand tall with its hair on end (piloerection) to appear larger and more intimidating. Conversely, a submissive individual presenting a fear grimace might simultaneously crouch low to the ground. The position of the tail can also signal mood or intent. Vocalizations, from coos and grunts to sharp alarm calls, add another layer of meaning.