Within‐group social bonds in white‐faced saki monkeys (Pithecia pithecia) display male–female pair preference

Abstract

White-faced saki monkeys (Pithecia pithecia) lack most of the behavioral and physical traits typical of primate monogamy [Fuentes, 1999]. In order to determine if social bonds in this species reflect patterns displayed by pair-bonded groups or larger multimale-multifemale groups, we draw on 17 months of data collected on wild white-faced sakis at Brownsberg Nature Park, Suriname. We analyzed within-group social bonds for three habituated groups (one two-adult and two multiadult groups) by measuring grooming, proximity, and approach/leave patterns between adult and subadult group members. We found that both two-adult and multiadult groups showed significantly stronger social bonds between a single male-female dyad within each group (deemed "primary dyads"). In all three groups, primary dyads were composed of the oldest adult male and a breeding female. These pairs had significantly higher levels of grooming than other within-group dyads and were also in close proximity (<1 m) more often than nonprimary dyads. Grooming in primary dyads was nonreciprocal, and consistently biased toward female investment. Grooming patterns in nonprimary dyads varied, but were often more reciprocal. Grooming and proximity of the primary dyad also changed in relation to infant development. Our results suggest that while white-faced sakis do not show behavioral and physical traits typical of monogamy or pair-bonding, social bonds are strongest between a single male-female pair. Pitheciine social systems range from small group monogamy in Callicebus to large multimale-multifemale groups in Chiropotes and Cacajao. As the middle taxon in this platyrrhine radiation, behavioral strategies of white-faced sakis provide a model for how social bonds and affiliation could be influenced by and affect the evolution of larger group size in primates.

The evolution of pair‐living, sexual monogamy, and cooperative infant care: Insights from research on wild owl monkeys, titis, sakis, and tamarins

“…For example, our examination of 12 years of data on group composition and demography for six social groups of sakis indicated that during 45% of group‐months, groups contained two or more adult females and/or two or more adult males (Van Belle, Fernandez‐Duque, & Di Fiore, ). That is, groups of equatorial sakis were often not “pair‐living,” an observation that is consistent with observations for other pitheciines (Thompson, ; Thompson & Norconk, ). Moreover, we have also documented several cases when more than one adult female (including mother‐daughter pairs) reproduced in the same group at the same time, belying characterization of P. aequatorialis as either sexually or genetically monogamous.…”

Demography and life history of wild red titi monkeys (Callicebus discolor) and equatorial sakis (Pithecia aequatorialis) in Amazonian Ecuador: A 12‐year study

“…Together, these observations suggest a more flexible grouping pattern for this species than previously presumed. Our observations are in line with grouping patterns reported for P. pithecia living in pristine forest at Brownsberg Nature Park, Suriname, where multi-year observations have revealed that two-adult groups may gradually accumulate offspring over time as some offspring have been observed to mate in their natal group or inherit the home range of their parents [Thompson & Norconk, 2011]. Our findings suggest that a variable grouping pattern is not restricted to P. pithecia alone, but might also be characteristic of Amazonian sakis.…”

Proximity association in polygynous western black crested gibbons ( Nomascus concolor jingdongensis ): network structure and seasonality

“…This has been reported in small primates such as titis monkeys (Callicebus discolor: de Luna et al, 2010) and saki monkeys (Thompson & Norconk, 2011), as well as in white-handed gibbons (Hylobates lar: Reichard, 2003) and siamangs (Symphalangus syndactylus: Lappan, 2008). In our study area, gibbon infants face predation from eagles (Spilornis cheela) (personal observation), and obviously dependent offspring (InR) would most likely require protection.…”

“…Even among young gibbons, individuals also maintained proximity with individuals of the same matrilineal line. When the dependent offspring grew older, the proximity between mother and offspring declined, as observed in saki monkeys (Pithecia pithecia: Thompson & Norconk, 2011).…”