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Exaggerated Sexual Swellings and the Probability of Conception in Wild Sanje Mangabeys (Cercocebus sanjei)


Carola Borries

Diane Doran-Sheehy

Carolyn L. Ehardt


© 2017, The Author(s). Females of several catarrhine primate species exhibit exaggerated sexual swellings that change in size and coloration during the menstrual cycle and, in some species, gestation. Although their function remains under debate, studies indicate that swellings may contain information males could use to discern ovulation and the probability that a cycle will be conceptive. Here we combine visual ratings of swellings with hormonal data for a group of Sanje mangabeys (18 adult, 3 adolescent females) to determine if their swellings provide reliable information on female fertility. In all cases where ovulation was detected (N=7), it occurred during maximum tumescence, and in 83.3% during the first two days of the “shiny phase,” a period during maximum tumescence when the swelling was brightest. There were no significant differences in maximum tumescence and shiny phase duration among cycles of different probability of conception, although there was a trend toward conceptive cycles exhibiting shorter shiny phases than nonconceptive ones. Only 25% (N=4) of postconceptive swellings developed the shiny phase, and adolescents displayed the longest maximum tumescence and shiny phases. The conspicuous nature of the shiny phase and the frequent overlap between its onset and ovulation suggest that its presence serves as a general signal of ovulation and that the cycle has a high probability of being conceptive. It also suggests that swellings in some Sanje mangabeys are more accurate signals of fertility than in other primates.


Borries, C., Fernández, D., Doran-Sheehy, D., & Ehardt, C. L. (2017). Exaggerated Sexual Swellings and the Probability of Conception in Wild Sanje Mangabeys (Cercocebus sanjei). International Journal of Primatology, 38(3), 513-532.

Journal Article Type Article
Acceptance Date Mar 3, 2017
Publication Date Jun 1, 2017
Journal International Journal of Primatology
Print ISSN 0164-0291
Publisher Springer Verlag
Peer Reviewed Peer Reviewed
Volume 38
Issue 3
Pages 513-532
Keywords adolescent, estradiol, paternity confusion, postconceptive swelling, sexual conflict
Public URL
Publisher URL
Additional Information Additional Information : The final publication is available at Springer via


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