International Journal of Primatology

, Volume 30, Issue 6, pp 777–789 | Cite as

Sexual Skin Color Contains Information About the Timing of the Fertile Phase in Free-ranging Macaca mulatta

  • Constance Dubuc
  • Lauren J. N. Brent
  • Amanda K. Accamando
  • Melissa S. Gerald
  • Ann MacLarnon
  • Stuart Semple
  • Michael Heistermann
  • Antje Engelhardt


Females of several primate species undergo cyclical changes of their sexual skin, i.e., the development of a swelling or a change in color. The relationship between intracycle probability of fertility and the size of sexual swellings is well established, but in the only study to combine an objective measure of color with endocrinological data, researchers found no evidence that swelling color contains such information. To evaluate the role of female skin color in the context of sexual signaling further, we investigated whether changes in sexual skin color contain information about the timing of the fertile phase in rhesus macaques (Macaca mulatta), a species in which adult females do not develop sexual swellings, but do express visually detectable changes in the skin color of the face and hindquarters. Using an objective and quantitative measure of color, along with detailed data on fecal progestogen and estrogen metabolite levels collected from 8 females of the Cayo Santiago colony, we show that the ratio of red to green (R/G) for facial and hindquarter skin significantly varies throughout the ovarian cycle. In addition, facial skin R/G is significantly higher during the 5-d fertile phase versus the 5-d periods immediately before or after this time, but no such pattern occurs in hindquarter R/G. This suggests that skin color change in female rhesus macaques may potentially signal information about the intracycle probability of fertility to male receivers, but that only facial skin color may signal reliable information about its timing.


color fecal steroids fertile phase Macaca mulatta sexual skin 



We thank the Caribbean Primate Research Center for permission to undertake research on Cayo Santiago; Juliet Alla, Julie Cascio, Camille Guillier, Edith Hovington, and Charlie McIntyre for assistance in data collection; Andrea Heistermann and Jutta Hagedorn for technical assistance in hormonal extraction and analysis; and the CPRC employees. We thank James Higham for inviting us to contribute to this special edition of the International Journal of Primatology on primate coloration. We thank Christoff Neumann for fruitful discussions; Roger Mundry for statistical advice; and Bernard Chapais, James Higham, and 2 anonymous reviewers for insightful comments on an earlier version of the manuscript. This project was funded by PhD fellowships awarded to C. Dubuc (SSHRC and Université de Montréal) and L.J.N. Brent (NSERC and Roehampton University). The investigation was approved by the IACUC of the University of Puerto Rico, Medical Sciences Campus. This publication was made possible by Grant No. CM-20-P40RR003640 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of NCRR or NIH.


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Copyright information

© Springer Science+Business Media, LLC 2009

Authors and Affiliations

  • Constance Dubuc
    • 1
    • 2
  • Lauren J. N. Brent
    • 3
  • Amanda K. Accamando
    • 4
  • Melissa S. Gerald
    • 4
    • 5
  • Ann MacLarnon
    • 3
  • Stuart Semple
    • 3
  • Michael Heistermann
    • 2
  • Antje Engelhardt
    • 2
  1. 1.Département d’AnthropologieUniversité de MontréalMontréalCanada
  2. 2.Department of Reproductive Biology, German Primate CentreGöttingenGermany
  3. 3.Centre for Research in Evolutionary AnthropologyRoehampton UniversityLondonUK
  4. 4.Cayo Santiago, Caribbean Primate Research CenterUnit of Comparative Medicine, Department of Medicine, University of Puerto RicoPunta SantiagoUSA
  5. 5.Department of Internal MedicineUniversity of Puerto Rico Medical SchoolSan JuanUSA

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