Ape signals description

©Emilie Genty

In the following tables you will find a description and some illustrations of the ape signals (gestures, body signals, vocalizations, facial expressions) included in the template. These lists are not exhaustive but include all the signals that have been observed and analyzed for the purpose our different studies.

Ape gestures

Gestures in the following table were illustrated by Sidney Maffini.

(see Byrne et al. 2017¹ for a comparison of gesture repertoires across ape species)

Gesture	Modality A=audible S=silent visible T=tactile	Description	Illustration
Beckoning arm	S	Stretching arm toward another, followed by a sideways sweeping movement of the arm toward the self and ending with a twirl of the wrist from palm upward to downward, indicates invitation to approach and follow
Beckoning head	S	Head jerking movement on side indicating a direction to follow
Beckoning shoulder	S	Exaggerated movement of shoulder and arm when standing up or turning to walk away, indicates direction of travel movement, accompanied by recipient monitoring (look back), invitation to follow	Coming soon
Big loud scratch	A	Loud exaggerated scratching movement on own body (supposedly intentional to indicate location of desired grooming)	Coming soon
Clap hands	A	Tapping both palms of hands against each other	Coming soon
Clap feet	A	Tapping both sole of feet against each other
Climb-on	S	Sweeping movement of the arm over own opposite shoulder, invitation to climb on back
Directional Hand-on	T	Touching other’s body part (usually back) with palm of hand and maintaining touch for more than 2 s to orient other in a desired direction
Directional push	T	Gentle push on another’s body part with hand(s), arm(s), feet or head, to orient partner’s body in desired direction
Drum_other	A/T	Drumming other’s body part with fists or palms
Drum object	A	Drumming an object with fists	Coming soon
Embrace	T	Signaller wraps arm(s) around recipient and maintains physical contact
Fingers flex	S	Stretching hand out toward another with rapid alternation of stretching and bending movements of fingers
Flap	S	Raising one arm and hand and making a downward slapping movement of the arm in front of another, in the air	TO ADD
Flap leg	S	Sitting with knees bent, one or both legs opened and closed to the side (single or repeated)
Flap with object	S	Raising one arm and hand and making a downward slapping movement of the arm in front of another with object held in hand, in the air	Coming soon
Grab	T	Grabbing gently another’’s body part with closed hand(s)
Grab-pull	T	Grabbing gently another ‘s body part with closed hand(s) and pulling towards self
Hand on	T	Touching head (or other body part) of another with palm(s) of hand(s) and maintaining touch for more than 2 s
Head bob	S	Bobbing head up and down
Head jerk	S	Throwing chin upwards abruptly
Head nod	S	Nodding head up and down in the body x axis
Head butt	T	Touching head (or other body part) of another with head and maintaining touch for more than 2 s	Coming soon
Hide	S	Hidding own body part, (e.g. face, genitals,…) with hand(s) or arm(s)	Coming soon
Hit with object	T	Hitting another with object held in hand	Coming soon
Hit object	A	Hitting object with closed fist	Coming soon
Hit object with object	A	Hitting object with object held in hand	Coming soon
Kick	T	Kicking another’s body with foot	Coming soon
Knock object	A	Hitting an object forcefully and multiply with fist or wrist	Coming soon
Leaf clip	A	Strips are torn from a leaf/leaves using hand or mouth, making a conspicuous rhythmic sound	Coming soon
Move object	S	Grabbing an object with hand (s) and moving it away or pulling it	Coming soon
Out arm	S	Raising one (both) arm(s) laterally on side of body at about shoulder level
Out leg	S	Raising one leg at hip level (like a dog peeing)
Poke	T	Touching firmly and briefly another’s body part with finger, may be repetitive
Punch	T	Hitting another forcefully and singly with fist(s) or wrist(S)	Coming soon
Push	T	Pushing away gently another with hand(s) or arm(s)
Raise arm	S	Raising one (both) arm(s) above head level
Raise leg	S	Raising one leg above hip level	Coming soon
Rap object	A	Rapping object on the ground back and forth repetitively	Coming soon
Reach hand	S	Holding a hand toward another by extending the arm and hand
Reach leg	S	Holding a foot toward another by extending the leg and foot	Coming soon
Shake arm	S	Shaking loosely one (both) arm(s) from shoulder joint
Shake feet	S	Shaking feet vigorously and loosely from ankle joint
Shake hand	S	Shaking hand vigorously and loosely from wrist joint
Shake head	S	Shaking head from side to side on horizontal axis	Coming doon
Shake object	S	Shaking fixed object forcefully with one or both hands
Shake other	T	Shaking other’s body part with one or both hands	Coming soon
Shoo (Hand wave off)	S	Raising hand and waving it away from self
Slap	T	Slapping forcefully and singly another with palm of hand	Coming soon
Slap object	A	Slapping forcefully and singly object with palm of hand
Stomp single	A	Stamping ground forcefully with sole of foot
Stomp rhytmic	A	Stamping ground forcefully and alternatively with one foot then the other very rapidly
Stretch over	S	Stretching and raising arm till about head level with the palm facing downwards, like embracing another’s body without touching, sexual invitation
Stroke	T	Stroking another individual’s body with gentle back and forth movement of palm of hand or fingers
Swing arm	S	Swinging arm back and forth on side of body, either once or repetitively
Swing leg	S	Swinging leg(s) back and forth on side of body, either once or repetitively	Coming soon
Swing under arm	S	Swinging arm back and forth from front of body to between legs
Tap	T	Tapping repetitively another with palm of hand, with firm short contact of the fingers to the other’s body (may include rhythmic repetition or single movement)
Tap object	A	Tapping an object repetitively with palm of hand
Throw object	S	Throwing an object in direction of another
Throw threat	S	Grabbing an object and performing a forward and forceful movement but the object is not released
Touch	T	Touching gently another individual’s body part with palm of hand, for under 2s
Wave arm	S	Waving arm(s) raised above shoulder level with large back and forth movements

Ape body signals

Body signal	Modality A=audible S=silent visible T=tactile	Description	Illustration
Bite	T	Holding another’s body part between lips or teeth without pressure (mock bite)	Coming soon
Bounce	S	Standing on four relaxed limbs and performing rapid up and down movements	Coming soon
Bow	S	Bending forward upper body according to the body x axis while standing on two legs	Coming soon
Dangle	S	Hangs from arm(s) above another, may shake feet/legs, typically audible with movement in trees	Coming soon
Dragging object	A	Dragging object held in hand along side of body (usually branch) while moving forward, charging display	Coming soon
Gallop	A	Exaggerated running with forelegs playfully and forcefully stamping the ground (similar to a child imitating a horse galloping	Coming soon
Gallop stiff	S	Running with stiff forelegs	Coming soon
Jump	S	Both feet leave ground simultaneously with horizontal displacement	Coming soon
Look	S	Holding eye-contact with another lasting >2s	Coming soon
Open arm	S	Subtle opening of the arm, invitation to body contact	Coming soon
Open leg	S	Subtle opening of the leg, invitation to body contact	Coming soon
Pirouette	S	Twirling movement of whole body around the body y axis while standing on four legs. Progressive forward movement in space	Coming soon
Pounce	T	Displacing through air to land quadrupedally on the body of another	Coming soon
Present bipedal	S	Standing bipedally in front of another with arms spread apart, sexual invitation	Coming soon
Present concave back	S	Sitting in front of another with arched back to expose genitals with legs spread apart, sexual invitation	Coming soon
Present rump	S	Standing quadrupedally in front of another with dorsal side up to expose hindquarters, while looking back at recipient, sexual invitation	Coming soon
Present ventral	S	Lying on back in front of another with legs spread apart to expose genitals	Coming soon
Present body part	S	Presenting body part by stretching body to deliberately expose an area of own body to another’s attention, usually to be groomed or invitation to climb-on	Coming soon
Push object	A	Pushing away forcefully an object with hand usually with body hunched over and accompanying a charging display	Coming soon
Rock	S	Rocking movement of whole body while seated	Coming soon
Rock bipedal	S	Rocking movement of whole body while standing bipedally	Coming soon
Roll over	S	Signaller rolls onto back exposing stomach, can be accompanied by repeated movements of arms and/or legs	Coming soon
Side roulade	S	Body is rotated around the head-feet axis while lying on the ground	Coming soon
Somersault	S	Twirling forward movement of whole body around the body x axis	Coming soon
Stiff stance	S	Standing rigidly with stiff limbs and forelimbs held tight	Coming soon
Swagger bipedal	S	Lateral swaying of the upper body	Coming soon
Walk stiff	S	Walking with rigid forelegs, with a slow exaggerated movement	Coming soon
Walk tandem	T	Placing arm over the body of another and both walk forward while maintaining position	Coming soon

Ape vocalisations

Vocalisation	Description	Context of production	Illustration
Peeps	High-frequency, closed mouth vocalization. Short in duration and characterised by a simple, flat acoustic form composed of several harmonics that are generally un-modulated	Produced across a large array of contexts, especially common during feeding events and travel	(Clay et al.2015)2
High hoots	High-pitched long-distance call, like a ‘waah’	Long distance communication, can be used to communicate between parties and given in response to external disturbance or excitement (e.g. food arrival)
Contest hoots	Call sequences consisting of an introductory phase (modulated inverted u-shape form), an escalation phase composed of several stereotyped units (unmodulated inverted u-shape), and a let-down phase	Used by males to challenge another individual and display status to others	(Genty et al. 2014)3
Victim screams	High-pitched, with shrill and rasping sounds given at full vocal strength, large number of harmonics and long in duration, accompanied by teeth-baring (complete lip retraction, exposing both teeth and gums, the mouth may be wide open)	Used by victim after conflict or during tantrums
Copulation screams	Single or succession of high-frequency squeaks and screams	Used by females during mating events	(Clay and Zuberbühler, 2011)4
Pant laughter	Voiceless, jerky breathing which sounds like coarse low-pitched grunting, rather soft, accompanied by play-face	Used during socio-positive interactions, play, chase-play. Mostly given by subordinate to dominant
Laughter	Full laughter, sounds like a ‘ah-ah-ah’	Triggered by physical contact (tickle, bite)
Pant grunts (greeting grunts)	A rhythmic series of brief, grunt-like, vocalized air expulsion sounding like a ‘eh-eh-eh’	Close-range vocalisation, uttered during approaches from subordinates to dominants in agonistic situations
Alarm peep	Same as Peeps	Given in response to the discovery of a minor threat, or response to surprise
Pout moan (or Whimpers)	Low-pitched, melodious call sounding like a whining “hoo-hoo”27, accompanied by pout face (lips are pursed forward and curled outward in front resulting in circular opening).	Used by infants for requests, used by adults during sexual initiations, food begging, or as a appeasement signal in agonistic interactions. Also used as a request to stop current activity	(Genty, 2019)5
Threat Barks	Same as barks	Used during aggressive attacks, or if bothered by another individual approach or behaviour
Wieew bark	A single, very loud bark, accompanied by facial expression of wide open mouth. Difficult to distinguish from high hoots	Given in response to alarm or hostility rather than excitement.
Raspberry	Voiceless sounds, air is pressed through the lips, like a ‘prrrrr’	Used during grooming, or food begging

Ape facial expressions

Facial expression	Description	Context of production	Illustration
Silent bare-teeth	Retraction of the lips resulting in partial or complete exposure of the teeth and gums, with mouth practically closed and without vocalization	Displayed in agonistic and approach-retreat interactions, during sexual interactions. Performed by both subordinate and dominant individuals, expression of fear, nervousness, or hesitation. Demonstrates non-hostile intentions, function as appeasement and reassurance signal.	©Emilie Genty
Tense mouth	Lips show strong horizontal tension. They are either drawn inward or slightly bar- ing the teeth. The mouth may be opened but never widely. No vocaliza- tions accompany the display	Aggressive expression, before or during display behaviours. Displayed also in food competition situations
Pout face	Lips are pursed forward and curled outward in front resulting in a circular opening. The lips are pressed together at the mouthcorners	Displayed to request for food or request physical contact. Sometimes displayed during grooming. Can express disappointment	©Emilie Genty
Play-face	Mouth is opened with the lips either a) in a relaxed position covering the upper teeth completely and the lower teeth partially, or b) retracted, without however pulling back the mouth resulting in baring of both the upper and lower and frontal teeth	Displayed during play invitation or play bouts	©Emilie Genty

1. Byrne R.W., Cartmill E. Genty E., Graham K. E., Hobaiter, C.,Tanner J (2017). Great ape gestures: Intentional communication with a rich set of innate signals. Animal Cognition. 20, 755–769 (2017). ↩

2. Clay Z., Archbold J. Zuberbühler K. (2015). Functional flexibility in wild bonobo vocal behaviour. PeerJ 3, e1124. ↩

3. Genty E., Clay Z., Hobaiter C., & Zuberbühler K. (2014). Multi-modal use of a socially directed call in bonobos. PloS one, 9(1), e84738. ↩

4. Clay Z, Zuberbuhler K (2011) The structure of bonobo copulation calls during reproductive & non-reproductive sex. Ethology 117: 1158–1169. ↩

5. Genty E. (2019). Vocal–gestural combinations in infant bonobos: new insights into signal functional specificity. (2019). Animal Cognition 22, 505–518 https://doi.org/10.1007/s10071-019-01267-0. ↩