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

Social Flexibility in the Classically Monogamous Titi Monkey: A Response to Increased Population Pressure


Anthropology, Indiana University, Bloomington

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Titi monkeys typically reside in small groups consisting of a breeding pair and dependent offspring. Traditionally they are believed to be the only primates strictly conforming to the classic monogamous profile being monomorphic , forming tightly bonded pairs maintained by coordinated displays, and territorial with a high level of paternal investment. Observations from a long-term field study of Callicebus donacophilus in Santa Cruz, Bolivia, however, reveal a much more flexible social system. In October of 2009, we observed a two-adult male, resident male plus male from adjacent territory, and one female grouping. Both males resided in the group providing infant care until the resident male was ousted in January 2010. A two breeding female, resident female plus female from nearby group, and one male grouping was first observed in September 2011. The male simultaneously cared for both infants born to the group that season, although displaying a social preference for the resident female. Fecal samples have been collected from both groups for genetic paternity testing. The observed social arrangements can likely be attributed to increased population pressure as a result of population growth and further degradation of their fragmented habitat. Territories overlap considerably at Yvaga Guazu and there appears little opportunity for new territory formation, thus resulting in novel social behavior.

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