Document Type


Date of Degree Completion

Spring 2015

Degree Name

Master of Science (MS)


Primate Behavior

Committee Chair

Lori K. Sheeran

Second Committee Member

Ralf Greenwald

Third Committee Member

Jessica A. Mayhew


I explored gestures used by captive Javan gibbons (Hylobates moloch) at the Gibbon Conservation Center (Santa Clarita, CA). I hypothesized that a sender gibbon’s gesture modality would vary with the recipient gibbon’s attentional state and the sender would be equally likely to use all modalities (tactile, visual, actions, and facial expressions) when the recipient was attending (facing the sender), but would use more tactile gestures and actions when the recipient was non-attending (oriented away from the sender). I collected data from 10 individuals using all-occurrences sampling and an ethogram to score behaviors from video recordings. In 1,143 interactions, gibbons used visual gestures and facial expressions significantly more when the recipient was attending and tactile gestures significantly more when the recipient was non-attending. There was no significant difference in actions. These data show that juvenile Javan gibbons used gestures appropriate to recipient’s attentional state in three out of the four modalities.