THE EFFECTS OF AGING ON SOCIAL BEHAVIOR IN MALE AND FEMALE RHESUS MACAQUES
OF CAYO SANTIAGO
DISSERTATION
Presented in Partial Fulfillment of the Requirements
for the Degree Doctor of Philosophy in
the Graduate School of The Ohio State University
By
Judith A. Corr, M.A.
The Ohio State University
2000
Dissertation Committee:
Professor Douglas E. Crews, Advisor
Professor Paul Scuilli
Professor Sarah Boysen
Professor Scott McGraw
ABSTRACT
Human demographics are shifting toward an increased proportion of
aged individuals which in turn increases the need for information about the
basic processes of biological and social aging. All primates share a
common ancestor, naturally extending interest in aging across primate
species. This study investigates the relationship between chronological age
and social behavior in 42 adult male and female rhesus macaques (Macaca
mulatta). Three male and three female (6) groups were formed and each
divided into age classes containing all available 'old' (20+) individuals
and randomly selected comparison samples of younger adults. Observational
data were collected (625 hours) and evaluated with regard to existing human
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 females while old males are more social than other 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
others in non-social behaviors, d) old females have smaller social networks
than other females while old males have larger social networks than other
males, and d) females of all ages prefer daughters as social partners,
while young and middle-aged males prefer adult females and old males prefer
infants and 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.
TABLE OF CONTENTS
Abstract.....ii
Dedication.....iv
Acknowledgements.....v
List of Tables.....x
List of Figures.....xii
Chapters:
1. Introduction.....1
Theory in human aging.....3
Aging research in nonhuman primates.....6
Prior work.....8
The present study.....11
2. Methods and Materials.....14
Research area.....14
Subjects.....16
Sampling.....19
General analysis.....23
Definitions and specific methods.....23
3. Disengagement in aged monkeys.....30
Data analysis.....32
Results: Females.....34
Results: Males.....46
Other theories of aging.....47
4. Social Roles.....51
Data analysis.....54
Results: Females.....54
Results: Males.....64
5. Social Networks.....66
Data analysis.....67
Results: Females.....76
Results: Males.....82
6. Discussion / Conclusion.....88
Strengths of the project.....89
Methodological limitations.....91
Social interactions.....92
Social roles.....95
Social network characteristics.....101
Conclusion.....103
Future research.....104
Bibliography.....108
Appendices
A. Software configuration.....116
B. Individual Female Summary Data.....136
C. Individual Male Summary Data.....170
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June 28, 2001
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