Conflicts of interest: None.
Variation in Scrotal Color Among Widely Distributed Vervet Monkey Populations (Chlorocebus Aethiops Pygerythrus and Chlorocebus Aethiops Sabaeus)
Article first published online: 19 APR 2013
© 2013 Wiley Periodicals, Inc.
American Journal of Primatology
Special Issue: Special Issue on Primate Signals
Volume 75, Issue 7, pages 752–762, July 2013
How to Cite
CRAMER, J. D., GAETANO, T., GRAY, J. P., GROBLER, P., LORENZ, J. G., FREIMER, N. B., SCHMITT, C. A. and TURNER, T. R. (2013), Variation in Scrotal Color Among Widely Distributed Vervet Monkey Populations (Chlorocebus Aethiops Pygerythrus and Chlorocebus Aethiops Sabaeus). Am. J. Primatol., 75: 752–762. doi: 10.1002/ajp.22156
- Issue published online: 15 MAY 2013
- Article first published online: 19 APR 2013
- Manuscript Accepted: 22 MAR 2013
- Manuscript Revised: 20 MAR 2013
- Manuscript Received: 27 JUN 2012
- NSF. Grant Number: BCS0629321
- NIH. Grant Number: R01RR0163009
- University of Wisconsin-Milwaukee Graduate School and Dissertation Fellowships
- vervet monkeys;
- body color display
Vervet monkeys (Chlorocebus aethiops) exhibit bright blue scrotal skin which may function to mediate social interactions by acting as a socio-sexual signal. Previous research on scrotal coloration among vervet monkeys was limited to experimental work on captive Ch. a. sabaeus, the least colorful vervet subspecies, and two field studies of the more colorful Ch. a. pygerythrus. In a study of free-ranging and captive vervet monkeys in South Africa (Ch. pygerythrus), West Africa (Ch. a. sabaeus) and the Caribbean (Ch. a. sabaeus), we examined scrotal color variation across geographically distant subspecies. We provide an exploration of how digital photographs may be used to quantify and analyze blue and green skin coloration by examining the blue–yellow opponency channel and luminance channel as color measures. We found that that at all ages the scrotal color of Ch. a. pygerythrus males was always bluer and darker than that of Ch. a. sabaeus males. Among Ch. a. pygerythrus scrotal color becomes bluer and lightens with increasing age, while the color of Ch. a. sabaeus males also lightens, but becomes less blue with increasing age. We suggest that color variation is related to maturation and may function as an age-related signal among Ch. a. pygerythrus and Ch. a. sabaeus. We also found color was related to three morphological features among adults. For Ch. a. pygerythrus, higher body weight is associated with more blue color and longer canine length is associated with lighter color. Lighter color was associated with longer body lengths among Ch. a. sabaeus. Future studies focused on color variation within age classes are needed to examine the potential signal content of color in this species. Am. J. Primatol. 75:752–762, 2013. © 2013 Wiley Periodicals, Inc.