SEX, AGGRESSION, AND AFFILIATION: THE SOCIAL SYSTEM OF WHITE- FACED SAKI MONKEYS (PITHECIA PITHECIA) A dissertation submitted to Kent State University in partial fulfillment of the requirement for the degree of Doctor of Philosophy by Cynthia L. Thompson August, 2011 Dissertation written by Cynthia L. Thompson B.S. University of California, Davis, 2004 M.A. Kent State University, 2006 Ph.D. Kent State University, 2011 Approved by ____________________________________, Dr. Marilyn A. Norconk Chair, Doctoral Dissertation Committee ____________________________________, Dr. C. Owen Lovejoy Member, Doctoral Dissertation Committee ____________________________________, Dr. Richard S. Meindl Member, Doctoral Dissertation Committee ____________________________________, Dr. Joan B. Silk Member, Doctoral Dissertation Committee Accepted by ____________________________________, Dr. Robert V. Dorman Director, School of Biomedical Sciences ____________________________________, Dr. John R. D. Stalvey Dean, College of Arts and Sciences ii TABLE OF CONTENTS LIST OF FIGURES .............................................................................................................v LIST OF TABLES ............................................................................................................. vi ACKNOWLEDGEMENTS .............................................................................................. vii Chapter I. INTRODUCTION ............................................................................................................1 Primate Social Systems ..............................................................................1 Study Species: Pithecia pithecia pithecia ..................................................3 Goals ...........................................................................................................9 II. GENERAL METHODOLOGY ....................................................................................10 Study Site .................................................................................................10 Study Subjects ..........................................................................................12 Sampling Techniques ...............................................................................15 III. SEXUAL BEHAVIOR AND REPRODUCTIVE STRATEGIES ..............................17 Introduction ..............................................................................................17 Methods ....................................................................................................21 Results ......................................................................................................26 Discussion ................................................................................................39 Conclusions ..............................................................................................48 IV. WITHIN-GROUP SOCIAL BONDS ..........................................................................49 Introduction ..............................................................................................49 Methods ....................................................................................................51 Results ......................................................................................................55 Discussion ................................................................................................64 Conclusions ..............................................................................................69 V. WHY FIGHT? THE ULTIMATE CAUSES OF BETWEEN-GROUP AGGRESSION .............................................................................................................70 Introduction ..............................................................................................70 iii Methods ....................................................................................................74 Results ......................................................................................................81 Discussion ................................................................................................92 Conclusions ..............................................................................................98 VI. SEX, LOVE, & VIOLENCE: BRINGING IT ALL TOGETHER ...........................100 The White-faced Saki Social System .....................................................100 Applying the Models ..............................................................................104 The Phylogenetic Perspective ................................................................107 Addressing Variation in Social System ..................................................109 APPENDIX A ..................................................................................................................111 APPENDIX B ..................................................................................................................114 REFERENCES ................................................................................................................115 iv LIST OF FIGURES 1. Distribution of white-faced (Pithecia pithecia pithecia) and golden-faced saki monkeys (Pithecia pithecia chrysocephala) .....................................................................4 2. White-faced saki monkey sexual dichromatism ..............................................................5 3. Map of study groups‘ home ranges ................................................................................11 4. Group history of white-faced sakis at Brownsberg Nature park....................................13 5. Hormonal profiles of PF showing reproductive categories ...........................................25 6. Copulation patterns of study subjects, by group ............................................................28 7. χ2 of copulations by reproductive status. .......................................................................30 8. Copulation patterns of Mazaroni group females by reproductive status .......................31 9. Genital inspection and copulation rate by month, all groups pooled .............................34 10. Proximity within 1m by dyad ......................................................................................56 11. Grooming time attributable to each dyad type, by group ............................................57 12. Grooming reciprocity ...................................................................................................58 13. χ2 residuals for primary dyad proximity changes by infant status. ..............................62 14. Changes in grooming time and reciprocity of primary dyads by infant status ............63 15. ITE characteristics and dietary components, by month ...............................................82 16. ITE rate, intensity of aggression, copulation rate, and day path length by month.......83 17. Participation in ITEs by group, sex, and individual .....................................................84 18. Occurence of ITEs in relation to female reproductive state ........................................87 19. Difference in dietary components by intensity of aggression. .....................................90 20. Interrelationship between aspects of white-faced saki social system ........................103 21. Phylogenetic relationships of the pitheciines .............................................................108 v LIST OF TABLES 1. Female reproductive characteristics of white-faced saki monkeys ..................................7 2. Group composition of white-faced sakis during the current study at Brownsberg Nature Park, Suriname .............................................................................................................14 3. Genital inspections by sex and dyad ..............................................................................32 4. Logistic regression of the effect of female reproductive status on males‘ decision to copulate .........................................................................................................................36 5. Copulation interference and harassment. .......................................................................36 6. Summary of copulation harassment/interference in Mazaroni group. ...........................37 7. Mating system and social organization of white-faced saki groups at Brownsberg Nature Park ....................................................................................................................40 8. Expected patterns of within-group social bonds by social structure ..............................51 9. Grooming equality indexes for Junco and Mazaroni groups .........................................60 10. Proximity, proximity maintenance, and grooming reciprocity of sexually active dyads .................................................................................................................60 11. Expectations for hypotheses explaining aggressive ITEs ............................................73 12. Scale of intensity of aggression during ITEs ...............................................................75 13. Multiple regression for predictors of ITE frequency ...................................................86 14. Best regression models for predicting ITE frequency, using AICC selection method .86 15. Multiple logistic regression for predictors of ITE intensity of aggression ..................88 16. Logistic