. Author manuscript; available in PMC: 2017 Feb 22.

Published in final edited form as: Ann Behav Med. 2016 Aug;50(4):487–496. doi: 10.1007/s12160-016-9773-0

Table 1.

Excerpt from a chimpanzee/bonobo ethogram

Behavior	Definition
Silent teeth-baring	“Retraction of the lips resulting in partial or complete exposure of the teeth and gums, with mouth practically closed and without vocalizing. The face is oriented toward the partner but the eyes may make evasive movements. Subtypes of the pattern can be distinguished dependent upon the amount of teeth exposure, and upon whether the lips arc curled outward or pulled flat.” p.190
Play face	“The 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 corners, resulting in baring of both the upper and lower frontal teeth. The second variant occurs both silently and in combination with the 'panting laugh.’ The two variants alternate and blend so frequently that it is hard to draw a line between them.” p. 197

Behavior

Definition

Silent teeth-baring

“Retraction of the lips resulting in partial or complete exposure of the teeth and gums,
with mouth practically closed and without vocalizing. The face is oriented toward
the partner but the eyes may make evasive movements. Subtypes of the pattern can
be distinguished dependent upon the amount of teeth exposure, and upon whether
the lips arc curled outward or pulled flat.” p.190

Play face

“The 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 corners, resulting in baring of both the upper and lower frontal teeth.
The second variant occurs both silently and in combination with the 'panting laugh.’
The two variants alternate and blend so frequently that it is hard to draw a line
between them.” p. 197

Note: This excerpt was extracted from de Waal’s “The communicative repertoire of captive bonobos (Pan paniscus), compared to that of chimpanzees.” [47]