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

One of the most commonly cited functional explanations for animal duet song s is strengthening of the pair bond. However, the evidence to support this view is, at best, limited. This study provides support by documenting a rel ationship between pair bonds and duet singing in siamangs. As a working hyp othesis, we assume that if duetting were related to pair bonding, we might expect to see a relationship between duetting intensity and indicators of p air bond strength. Like most gibbon species, siamang pairs produce loud, lo ng and well-coordinated duet songs. We recorded daily frequency and duratio n 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 w ith grooming activity and. behavioural synchronization, and negatively corr elated with distance between mates. These results suggest that the producti on of coordinated duets by siamang pairs is related to pair bonding. (C) 20 00 The Association for the Study of Animal Behaviour.