ORIGINAL PAPER Do females pay attention to secondary sexual coloration in vervet monkeys (Chlorocebus aethiops)? Melissa S. Gerald & James Ayala & Angelina Ruíz-Lambides & Corri Waitt & Alexander Weiss Received: 14 March 2007 / Revised: 16 September 2009 / Accepted: 17 September 2009 / Published online: 30 October 2009 # Springer-Verlag 2009 Abstract Several primate species show sexual dichroma- tism with males displaying conspicuous coloration of the pelage or skin. Studies of scrotal coloration in male vervet monkeys (Chlorocebus aethiops) suggest that it is an important intrasexual signal, with relatively dark, colourful males dominating paler males. To date, no studies have examined the influence of male colour on intersexual social interactions in vervet monkeys. The primary goal of the present study was to evaluate whether female vervet monkeys attend to male coloration. We experimentally introduced females, housed with either “pale” or “dark” males, to stimulus males whose scrota were pale, dark, or pale but painted to look dark. Overall, during introductions, females did not differ in time spent directing affiliative behaviour toward pale, dark, and painted males; however, females, permanently housed with dark males, spent significantly more time directing affiliative behaviour toward pale than painted males. When the stimulus male was pale, affiliative exchanges between males and females were longer than when the stimulus male was painted. Home male colour was not related to female-initiated aggression. Home male colour was also not related to male-initiated aggression, although painted stimulus males were more likely to initiate aggression than pale stimulus males. These findings lead us to conclude that females pay attention to male coloration, but do not bias their interactions toward males solely on the basis of natural male coloration. Keywords Colour . Signal . Genital . Sexual selection . Vervet monkeys . Primates Introduction Secondary sexual characteristics, including colour, plumage accoutrements, horns, and antlers are widespread across animal taxa (Darwin 1871; Andersson 1994). In some animals, these characteristics serve as armaments in intra- sexual competition, but are not involved in mate assess- ment, e.g., ring-necked pheasant (Phasianus colchicus) spur length (Mateos and Carranza 1996). In other animals, members of the opposite sex use these characteristics as a basis for mate selection, such as earwig (Forficula auricularia) forcep size (Radesäter and Halldórsdóttir 1993). Still, in other animals, particularly taxa with multiple ornaments, secondary sexual characteristics only appear useful as ornaments to attract mates, but serve no function in intrasexual competition, e.g., red-collared widowbird (Euplectes ardens) tail elongation (Pryke et al. 2001). Despite widespread colour differences between the sexes in primates, until recently, the study of primate ornamen- M. S. Gerald (*) : J. Ayala : A. Ruíz-Lambides : C. Waitt Cayo Santiago, Caribbean Primate Research Center, P.O. Box 906, Punta Santiago, PR 00741, USA e-mail: melissa.gerald@gmail.com M. S. Gerald Department of Internal Medicine, Medical Sciences Campus, University of Puerto Rico, San Juan, PR 00936-5067, USA C. Waitt John Krebs Field Station, Department of Zoology, University of Oxford, Wytham, Oxford OX2 8QJ, UK A. Weiss Department of Psychology, School of Philosophy, Psychology, and the Language Sciences, The University of Edinburgh, 7 George Square, Edinburgh EH8 9JZ, UK Naturwissenschaften (2010) 97:89–96 DOI 10.1007/s00114-009-0619-5