Gender differences in caring for infant Cebuella pygmaea: the role of infant age and relatedness.

This paper describes a three-part study of the parenting behaviors of 6 family groups of Cebuella pygmaea (pygmy marmosets). In the first part, the parenting patterns of undisturbed family groups housed under laboratory conditions were scored throughout the first 10 weeks following the birth of their second infant(s). To further investigate the role of infant age in determining parental behavior, caretaking patterns were studied after a brief separation of infants of varying ages from their families. Finally, an unrelated infant, age 1-5 weeks, was placed inside the home cage of each family, and caretaking of this novel infant was scored. The main findings that emerged from the study were: (1) sex differences in carrying the infants were dependent upon the age of the infant, i.e., adult females were the predominant carriers of infants less than or equal to 3 weeks of age and males (either adult or juvenile) the main carriers for infants greater than 3 weeks of age; (2) some caretaking behaviors, e.g., grooming and protective retrieval, were performed predominantly by the adult females throughout infancy; and (3) the relatedness of the infant, i.e., one's own vs. another's, appeared to primarily affect the behavior of adult females. In general, experimental manipulations confirmed results of the observational part of the study and thus may be useful paradigms for testing specific hypotheses about parental behaviors.