Comparative and Theoretical Approaches to Studying Sexual Selection in Primates

Primates exhibit amazing variation in traits that are likely to have arisen through sexual selection. Many of these traits play a role in visual or chemical communication. The striking countenance of a dominant male mandrill serves as a classic example [Setchell]. Scent marking in callitrichids is another form of communication that may be sexually selected [Heymann], while dichromatism is a complicated phenomenon that is likely to be influenced by many factors, including sexual selection [Gerald]. Other sexually-selected traits are behavioral, including female intrasexual competition for mates [Saltzman; Vervaecke et al.; Heymann], infanticide by males [Crockett] or females [Digby, 1995; Saltzman], and cryptic female choice [Reeder]. Finally, sexual selection itself may be influenced by the competitive regime, as mediated, for example, by demographic factors [Strier; Watson et al.]. Primatologists have made great strides in understanding sexual selection in primates. The chapters in this book, which I summarize here, highlight many of these exciting advances, while also illustrating the shift from descriptive accounts of primate biology to tests of hypotheses that have arisen from advances in mainstream behavioral ecology [Shahnoor & Jones]. One chapter in this volume, for example, investigates the potential for applying new models of reproductive skew to understand patterns of sexual selection in primates [Hager]. Skew models are one of the most influential conceptual frameworks to emerge in the last decade of behavioral ecology research [Clutton-Brock, 1998; Reeve et al., 1998; Johnstone, 2000]. Figure 1 shows the number of citations for “reproductive skew” in a search of ISI’s Web of Science for the years 1994 to 2001. When “primate” is included as an additional search term, however, no hits are obtained, illustrating the lack of attention by primatologists to this conceptual framework. Similarly, searching for the phrase “reproductive skew” produced only two