Rise to Power: A Case Study of Male Fecal Androgen and Cortisol Levels before and after a Non-Aggressive Rank Change in a Group of Wild White-Faced Capuchins (Cebus capucinus)

Abstract

We examined fecal androgen and cortisol levels in three adult male white-faced capuchin monkeys (Cebus capucinus) before and after a non-aggressive rank increase in one habituated group residing in the Santa Rosa Sector of the Área de Conservación Guanacaste, Costa Rica. Fecal samples (n = 116) were collected opportunistically between July 2006 and July 2007. Alpha males had higher mean androgen levels than subordinates, and acquisition of the alpha position was linked to an immediate increase in mean androgens. Cortisol levels also increased in the alpha male after acquisition of his new rank, though this increase was delayed relative to the change in rank. These results indicate that, during a non-aggressive rank change, androgen and cortisol levels in male white-faced capuchins are physiological responses to dominance rank, rather than precursors that facilitate rank acquisition.

Hormonal correlates of male life history stages in wild white-faced capuchin monkeys (Cebus capucinus)

“…However, prior studies from this population of C. capucinus have shown that fGC levels of adult females increase in response to a presumably stressful situation (change in male group composition; Carnegie et al, 2011b). Additionally, individual fGC levels increase with a rise in male dominance rank (Schoof et al, 2011) and decrease with increased habituation levels (Jack et al, 2008), both situations presumably associated with changes in stress. ACTH challenge in the closely related robust tufted capuchin, Sapajus (Cebus) apella , results in a cortisol increase (Torres-Farfan et al, 2009).…”

“…To our knowledge, this phenomenon has not been investigated or documented in male primates, though evidence to date clearly demonstrates that T levels vary throughout a male’s life. Additionally, variability in individual T levels has been documented among adult male primates according to ecological seasonality (e.g., Cerda-Molina et al, 2009; Gesquiere et al, 2011a; but see Strier et al, 1999), mating/breeding seasonality (Bales et al, 2006; Brockman et al, 1998; Girard-Buttoz et al, 2009; Gould and Ziegler, 2007; Lynch et al, 2002; Ostner et al, 2002; Ostner et al, 2011; but see Strier et al, 1999; see Place and Kenagy, 2000 for review of non-primates), group demography (Rangel-Negrín et al, 2011), dominance status (Arlet et al, 2011; Kraus et al, 1999; Muehlenbein et al, 2004; Muller and Wrangham, 2004a; Muroyama et al, 2007; Schoof and Jack, 2013; Setchell et al, 2008), and changes in dominance status (Alberts et al, 1992; Beehner et al, 2006; Brockman et al, 1998; Eberhardt et al, 1980; Mendoza et al, 1979; Rose et al, 1975; Schoof et al, 2011; Setchell and Dixson 2001a; Wickings and Dixson, 1992). …”

“…Dispersal from the natal group is another stressful event during male life history that has been linked with elevated GC levels (Alberts et al, 1992; Bergman et al, 2005). Like T, individual GC levels can fluctuate according to various socioecological conditions such as ecological seasonality (primates: Gesquiere et al, 2011a; non-primates: Romero, 2002 and Schradin, 2008), mating/breeding seasonality (Fitchel et al, 2007; Lynch et al, 2002; Setchell et al, 2010; see Place and Kenagy, 2000 for review of non-primates), group demography (Alberts et al, 1992; Bergman et al, 2005), individual dominance status (Arlet et al, 2009; Bergman et al, 2005; Gesquiere et al, 2011b; Muller and Wrangham, 2004b; Sapolsky, 1983, 2004, 2005; Schoof and Jack, 2013; Van Belle et al, 2009), and changes in dominance status (Alberts et al, 1992; Beehner et al, 2006; Brockman et al, 1998; Schoof et al, 2011; Wickings and Dixson, 1992). …”

“…Male white-faced capuchins do not attain adult body size until they are 10 years of age, an observation that is consistent with sexually dimorphic patterns of somatic growth in species where males are larger than females (Dixson, 2012). Even as adults, males do not fill out with the entire suite of secondary sexual characteristics (e.g., exaggerated brow ridges, large mandibular girth, broad shoulder girdle) until/if they attain alpha male status within a social group (Schoof et al, 2011). This dormancy in the development of the full suite of secondary sexual characteristics is likely related to androgen levels rather than individual propensities, as androgens are significantly higher in alpha than subordinate adults (Schoof and Jack, 2013, in press) and appear to reach peak levels only after a male attains alpha status (Schoof et al, 2011) (See Figure 1a and b).…”

“…Even as adults, males do not fill out with the entire suite of secondary sexual characteristics (e.g., exaggerated brow ridges, large mandibular girth, broad shoulder girdle) until/if they attain alpha male status within a social group (Schoof et al, 2011). This dormancy in the development of the full suite of secondary sexual characteristics is likely related to androgen levels rather than individual propensities, as androgens are significantly higher in alpha than subordinate adults (Schoof and Jack, 2013, in press) and appear to reach peak levels only after a male attains alpha status (Schoof et al, 2011) (See Figure 1a and b). Given that not all males attain alpha status, and there is considerable age overlap for alpha and subordinate adults, alpha males appear to constitute a distinctive life history phase.…”