The 82nd Annual Meeting of the American Association of Physical Anthropologists (2013)

Seasonal changes in song structure and calling behaviour of the Bolivian Grey Titi Monkey (Callicebus donacophilus)


1Institute of Landscape Ecology, Community Ecology Group, University of Münster, Münster, Germany, 2Department of Anthropology, Indiana University, Bloomington

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Perhaps the most striking feature of the genus Callicebus is the loud, resonating song duets produced by a mated pair. Duets are proposed to serve in territorial defense, mate-guarding and/or pair-bond maintenance. Here we examine variation in duet structure and calling behaviour in relation to the annual breeding cycle.

Analyses of sound recordings and behavioral data recorded from 2008 to 2011 at Parque Yvaga Guazu in Santa Cruz, Bolivia revealed significant differences in both song structure and calling behaviour.

Syllables used during the mating season are 8% longer than those of the birthing season. In addition, the calls of the mating season have an 18% lower fundamental frequency and a 12% smaller bandwidth. The maximum frequency lies 12% lower during the mating season. The peak frequency showed no significant changes.

GLMMs revealed that C. donacophilus vocalizes significantly less in the birthing season, but 60% longer in duration. We argue that pair movement is restricted due to the energetic constraints of a clinging infant therefore permitting longer but less frequent vocalizations from a set location. Reduced intra-pair proximity with the birth of an infant likely functions in infant guarding and pair-bond maintenance. Duets are performed from higher canopy position in the mating season increasing signal transmission and announcing a pairs mated status. Type 1 duets are the most frequent form of inter-pair acoustic communication throughout the breeding cycle. In sum, Callicebus donacophilus possesses a highly complex communication system capable of adapting to the varied demands of the reproductive cycle

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