Geissmann, T. & Orgeldinger, M. (1997): Pair bond and duet songs in siamangs (Hylobates syndactylus). In Taborsky, M. & Taborsky, B. (Eds.), Advances in Ethology, Vol. 32: Contributions to the XXV International Ethological Conference, Vienna, Austria, 20-27 August, 1997 (pp. 123). Berlin & Vienn: Blackwell (Abstract only).

Pair bond and duet songs in siamangs (Hylobates syndactylus)

T. Geissmann¹ & M. Orgeldinger

¹Institut für Zoologie, Tierärztliche Hochschule Hannover

Like most gibbon species, siamang pairs (Hylobates syndactylus) produce loud, long and well coordinated duet songs. Although strengthening of the pair bond has long been suggested to be one of the possible functions of these duets, few studies have been related to duet function in gibbons in general or siamangs in particular, and the conclusions they reached regarding the pair-bonding function have been contradicting. 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 any indicators of pair bond strength. In order to test this prediction, data on duetting activity and various behavioural variables believed to be possible indicators of pair bond strength were collected in 10 siamang groups observed in various zoos. In accordance with the hypothesis under test, we found duetting activity to be positively correlated with grooming activity and behavioural synchronisation between mates, and negatively correlated with inter-individual distance between mates. These results suggest that the production of coordinated duets by siamang pairs is related to pair-bonding. None of the possible indicators of pair bond strength is related to the duration of time since pair formation or to the age of the mates. This suggests that siamang pair bonds reach their final (probably pair-specific) strength relatively soon after pair formation and show little improvement or deterioration afterwards.