Contrasting effects of living in heterosexual pairs and mixed groups on the structure of social attraction in squirrel monkeys ( Saimiri)

The structure of social attraction was assessed in pair- and group-living squirrel monkeys ( Saimiri) using paired-comparison and single-stimulus preference tests. Effects of the social environment were most prominent in females. Females housed with a single male showed sharply increased attraction to like-sex strangers and less pronounced increase in attraction to opposite-sex strangers, as compared to group-living females. Differences between pair- and group-living males were in the same direction found with females, but less extreme. Most group-living monkeys strongly preferred familiar animals to strangers regardless of sex, and like-sex to opposite-sex familiars. Change in the structure of social attractions in response to variations in the composition of the social environment appears to be an important factor in the maintenance of the species-typical grouping pattern in the squirrel monkey.