The relationship between duet songs and pair bonds in siamangs, Hylobates syndactylus.

One of the most commonly cited functional explanations for animal duet songs is strengthening of the pair bond. However, the evidence to support this view is, at best, limited. This study provides support by documenting a relationship between pair bonds and duet singing in siamangs. As a working hypothesis, we assume that if duetting were related to pair bonding, we might expect to see a relationship between duetting intensity and indicators of pair bond strength. Like most gibbon species, siamang pairs produce loud, long and well-coordinated duet songs. We recorded daily frequency and duration of duetting and three generally accepted indicators of pair bond strength (mutual grooming, behavioural synchronization and distance between mates) in 10 siamang groups in zoos. Duetting activity was positively correlated with grooming activity and behavioural synchronization, and negatively correlated with distance between mates. These results suggest that the production of coordinated duets by siamang pairs is related to pair bonding. Copyright 2000 The Association for the Study of Animal Behaviour.