Monkey Facial Expressions and Emotions: What the Face Says

Monkeys have some of the most mobile faces in the animal kingdom, and they use them constantly. A single second of expression can settle a dispute, invite play, defuse a threat or start a fight. Reading those signals accurately is the difference between understanding a monkey and being badly bitten, because several expressions mean close to the opposite of what a human assumes.

The Grin That Is Not a Smile

The most misread expression in all of primatology is the bared-teeth display. A monkey pulling its lips back to show the teeth, often with the corners of the mouth drawn wide, is usually signalling fear, appeasement or submission, not happiness. In macaques this silent bared-teeth face is typically given by a subordinate to a dominant animal and is a way of saying that no challenge is intended. Photographs of monkeys captioned as smiling are almost always pictures of stressed animals, a misunderstanding covered further in monkey myths and misconceptions.

Lip Smacking and Friendly Signals

Lip smacking, a rapid soft opening and closing of the mouth sometimes with a tongue flick, is the everyday friendly signal in macaques and baboons. It is used on approach, before grooming, towards infants, and between reconciling opponents. Other affiliative signals include the ear flap, the raised brow with a relaxed mouth, and the presented back that invites grooming. These all belong to the same channel as the vocal and postural signals described in how monkeys communicate.

Threat Faces

Threats are unmistakable once learned. A direct stare with the brows raised and the eyelids pulled back exposes pale eyelid skin in many macaques and is a genuine warning. An open mouth with the canines visible and the lips forward is stronger still. Head bobbing, yawning that displays the canines, and slapping the ground or shaking branches escalate it. Mandrills and drills add colour to the message, an unusual case explained in why some monkeys have bright colours.

The Play Face

Play has its own signal: a relaxed open mouth without tension around the eyes, usually with the teeth partly covered, often combined with exaggerated loose movement and a bouncing gait. It functions as a promise that what follows is not serious, and it lets juveniles wrestle for long periods without escalation. Its role in development is explored in monkey play behaviour.

How Researchers Study Monkey Faces

Modern work uses coding systems adapted from human facial analysis, which map individual muscle movements rather than relying on impressions. Applied to macaques, these systems revealed that monkey faces are anatomically capable of far more distinct movements than earlier studies assumed, and that some expressions vary between species in the same way regional accents vary. Brain imaging has identified face-selective patches in the macaque temporal lobe, a finding that reshaped understanding of face processing in humans too, part of the wider story in monkeys in scientific research.

What About Emotions?

The careful answer is that monkeys clearly have emotional states, and that inferring the exact feeling behind them is difficult. Fear, anxiety, frustration and social contentment are well supported by hormones, heart rate, brain activity and behaviour together. Capuchins refuse to work for a poor reward when they can see a companion getting a better one, which looks a great deal like a sense of unfairness. Macaque mothers may carry a dead infant for days. Monkeys console after conflict and show behavioural signs of anticipation, boredom and depression-like withdrawal in barren conditions. What the evidence does not support is reading complex human narratives into a single photograph, and the related work on self-awareness is discussed in can monkeys recognise themselves in mirrors and monkey intelligence.

Reading Faces in Captivity

Anyone around monkeys needs this literacy. A bared-teeth face means back off, not come closer. A stare is a challenge, so returning it escalates. Yawning at close range is often a threat rather than tiredness. Chronic tension, pinned ears, and constant scanning point to an environment that is too exposed or too crowded. Practical context is in the beginners guide to monkey care and the daily care routine.

Frequently Asked Questions

Do monkeys smile?

Not in the human sense. The nearest equivalent, the bared-teeth display, usually signals fear or submission, while the relaxed open-mouth play face is the closest thing to a friendly grin.

What does lip smacking mean?

It is a friendly, tension-reducing signal used on approach, during reconciliation and towards infants.

Can monkeys recognise human expressions?

They read human faces and gaze direction well and respond to direct staring as a threat, though they do not interpret our expressions exactly as we do.

Do monkeys cry?

They vocalise in distress, but they do not shed emotional tears the way humans do.

Read next: why monkeys groom each other and what sounds monkeys make.