SOCIAL AGING IN FREE-RANGING RHESUS MACAQUES





JUDITH CORR, PhD

Grand Rapids, Michigan 45946




As human demographics continue to shift toward an increasing proportion of aged individuals, the need for information about the basic processes of both biological and social aging also increases. To date, however, 95% of published aging research is limited to the use of nonhuman primates as biological models for the mechanisms and pathologies of physiological senescence. Research including (or focusing on) primate behavioral gerontology is rare, resulting in the loss of valuable information.

This study investigates the relationship between chronological age and social behavior in 42 adult male and female rhesus macaques (Macaca mulatta.) Observational data were collected (625 hours) and evaluated with regard to existing human social gerontological theories. Analyses focused on the following questions: (1) does sociality vary across age classes, (2) are old monkeys a behaviorally distinct subgroup, and (3) do the characteristics of an individual's social network vary across age classes?

Results of analyses indicate that: a) old females are less social than other adult females while old males are more social than other adult males, b) old females and old males are distinct in their social behavior both from each other and others, c) neither old females nor old males are distinct from other adults in non-social behaviors, d) old females have smaller social networks than other adult females while old males have larger social networks than other adult males, and e) females of all ages prefer daughters as social partners, while young and middle-aged males prefer adult females and old males prefer yearlings.

All sexually reproducing organisms 'senesce,' that is, experience physiological decline with age, which can explain why old monkeys rest and sleep more than younger individuals. An explanation for the sex-based differences in aged social behavior and social networks reported in this study, however, may originate in rhesus matrifocal social structure. Related females remain in their matriline for life while males leave their birth families at adolescence and transfer into non-related groups throughout their adult lives. Strategies for 'successful' aging, i.e. survival, therefore, may vary by sex in aged rhesus.







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