Document Type


Date of Degree Completion

Spring 2018

Degree Name

Master of Science (MS)


Primate Behavior

Committee Chair

Lori K. Sheeran

Second Committee Member

Sofia Blue

Third Committee Member

Gabriella Skollar


I aimed to better understand captive gibbons’ pair bonds by studying behaviors that may indicate the relationship’s quality. I completed this research at The Gibbon Conservation Center (GCC) in Santa Clarita, California and observed four species: eastern hoolock (Hoolock leuconedys), Javan (Hylobates moloch), and pileated (Hylobates pileatus) gibbons; and a siamang (Symphalangus syndactylus). I conducted research from 19 April- 29 May 2017 using scan and focal animal sampling. I focused on nine pairs, and recorded gibbons’ grooming bouts, affiliative/agonistic/play behaviors, mating, behavioral synchrony, locomotion, and proximity. Previous researchers focused on duetting in relation to pair bonding more then other qualities of social behavior. The opportunity to study four different species at the same time adds new knowledge to gibbon social behavior. Learning more about captive gibbons’ social behavior, in particular pair bonding quality, could help conservation efforts, which is important most gibbons are Endangered. Rehabilitation and reintroduction programs are part of conservation efforts for helping to rebuild gibbon populations in the wild. Success of reintroduction into the wild in rehabilitation and reintroduction programs is measured by survival post-release, maintenance of the pair bond, and reproduction and survival of offspring. If the pairs are successfully cohabiting at the GCC, understanding behaviors indicating successful bonding may help predict survival once released. My results showed that pairs without offspring were in proximity significantly less and had significantly less occurrences of grooming bouts and affiliative behaviors. I found newly established pairs to be in proximity and behavioral synchrony significantly less than middle and long-term pairs. Newly established pairs had significantly more occurrences of affiliative and play behaviors than middle and long-term pairs. The mixed species pair was significantly in the most pair bonding behaviors. The hoolock pairs had more occurrences and were in grooming bouts significantly longer than other species. My results indicated that pair bonding behaviors might not be mutually exclusive of each other, so more than one behavior needs to be studied when trying to understand these complex social behaviors. I suggest further research into gibbon pair bond behaviors is needed to help staff at rehabilitation and reintroduction centers make decisions about gibbons’ release.