The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)

Sexual swellings of wild Sanje mangabeys (Cercocebus sanjei) in the Udzungwa Mountains of Tanzania


Interdepartmental Doctoral Program in Anthropological Sciences, Department of Anthropology, Stony Brook University, Stony Brook, NY, 11734

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The appearance of conspicuous sexual swellings during the fertile phase of the reproductive cycle is common to many catarrhine primates with multi-male mating systems, serving to function as some indication of female fertility. Ovulation typically occurs during maximum swelling, although since this period is frequently longer than the peri-ovulatory period, ovulation may not be possible to detect from swelling size alone. Changes in other physical attributes of the sexual swelling, however, might also serve to pinpoint the time of ovulation.

Here I describe sexual swellings and appearance in Sanje mangabeys (Cercocebus sanjei) living in the Udzungwa Mountains of Tanzania, and consider whether factors other than size may serve to pinpoint ovulation. I ranked the sexual swelling size of 23 adult females using a 9-point visual scale and concurrently collected fecal samples for analysis of ovarian hormones during a 21-month study. Results indicate that mean cycle length for parous females was 29.6 (± 3.1) days (n = 28), during 89% (26.3 ± 6.5 days; n = 37) of which females exhibited some swelling. Mean maximum swelling duration was 6.8 (±7.0) days (n = 41). However, within the maximum swelling period, its appearance changed, acquiring a darker and shinier tone for 4.4 (± 4.0) days (n = 25) just prior to detumescence. I will test whether this change is associated with ovulation from fecal estradiol and progesterone levels. If, as suspected, it coincides with ovulation this suggest that sexual swellings act as a reliable indicator of fertility in Sanje mangabeys.

This study was funded by NSF-DIGG (BCS 0925690), The Leakey Foundation, Margot Marsh Biodiversity Foundation, Primate Conservation Inc., Sigma Xi and Idea Wild.

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