Anthropology, University of Texas at Austin

March 26, 2015 10:15, Grand Ballroom E/F/G

Unidirectional dominance-related signals can be used to communicate submission (an immediate behavior) or subordination (an institutionalized behavioral pattern). Subordination signals are emitted during peaceful interactions and are hypothesized to be critical for the evolution of social complexity and robust power structures because they reduce uncertainty in social relationships. The chatter vocalization in Verreaux’s sifaka (Propithecus verreauxi) is a unidirectional submissive signal. To test the hypothesis that chatter vocalizations signal subordination and reduce agonism in a dyad, I examined 780 chatters from 18 dyads collected over 880 observation hours on 5 groups of sifaka in Kirindy Forest, Madagascar. Ninety-four percent of dyads exhibited chatters in the peaceful context, indicating that sifaka communicate about behavioral patterns rather than just immediate behaviors. Peaceful chatters in dyads significantly predicted groom rates, proportion of wins by dominants, and reconciliation but not fight rates. Thus, subordination signaling does not reduce conflicts in sifaka but does increase tolerance and affiliation when conflicts occur. Dyad type significantly predicted the frequency of peaceful chatters, with intrasexual dyads exhibiting chatters in peaceful contexts more often than intersexual dyads. Hence, intrasexual power may be more institutionalized than intersexual power. Sifaka have low rates of social interactions and while coalitions occur, they are uncommon. Therefore, the finding that subordination signaling is nearly ubiquitous in this lemur and less common in macaques suggests that triadic interactions may be less important for the evolution of social complexity than is currently thought and highlights the importance of studying social complexity in a variety of taxa.

This project was funded by the National Science Foundation #0002570, The Leakey Foundation, and Wenner-Gren Foundation.