Effects of reproductive and social variables on fecal glucocorticoid levels in a sample of adult male ring‐tailed lemurs (Lemur catta) at the Beza Mahafaly Reserve, Madagascar

Abstract

Glucocorticoids, a group of adrenal hormones, are secreted in response to stress. In male primates, variables such as breeding seasonality, dominance hierarchy stability, and aggressive and affiliative interactions can affect glucocorticoid levels. In this study, we examined interindividual differences in mean fecal glucocorticoid (fGC) levels among males in three groups of wild ring-tailed lemurs to better understand the physiological costs of group living for males in a female-dominant species that exhibits strict reproductive seasonality. Fecal and behavioral data samples were collected during one mating and two postmating seasons (2001 and 2003). The mean fGC levels were examined in relation to reproductive season, male rank, number of resident males, intermale and female-male agonism, and affiliative behavior with females. The mean fGC levels were not significantly elevated during mating season compared to the postmating period. During the mating season, male dominance hierarchies broke down and rank effects could not be tested; however, there was no relationship between male rank and fGC levels in the postmating periods. In 2001, males that resided in the group with the fewest males exhibited lower fGC levels during the postmating period. They also affiliated more with females than did males in the other groups. During the mating season of 2003, males engaged in more affiliative behaviors with females compared to the postmating season, but female-male agonism did not differ by season. However, rates of intermale agonism were significantly higher during mating compared to postmating periods, but such heightened agonism did not translate to a higher stress response. Thus, neither male-male competition for mates nor heightened agonism between males during the breeding season affected male fGC levels. Fewer males residing in a group, however, did have some effect on male-female affiliation and male fGC levels outside of the mating period. Males that live in a group with only a few (two or three) males may experience less physiological stress than those that live in groups with more males.

Crowding as a primary source of stress in an endangered fragment‐dwelling strepsirrhine primate

“…However, we found no difference in fGC levels in lactating females when compared to non-lactating females at either site, nor did males and females differ in fGC levels across the study period, despite different reproductive challenges at different times of year. Studies on L. catta from other sites have been inconclusive with respect to the role of reproductive state on stress levels (Cavigelli, 1999;Gould et al, 2005). It may be that, barring other physiological challenges, reproductive demands fall within the Predictive Homeostatic range (Romero et al, 2009) and thus do not induce major GC fluctuations.…”

“…GCs were extracted from fecal samples and measured via radioimmunoassay in accordance with procedures described elsewhere for L. catta (e.g. Cavigelli, 1999;Gould, Ziegler & Wittwer, 2005;Pride, 2005a,b,c;Starling et al, 2010; details in Supporting Information).…”

Sex, social status and physiological stress in primates: the importance of social and glucocorticoid dynamics

“…The majority of primate studies indicate that dominant males produce levels of GCs that are more than or equal to subordinate males, whereas only one study has found that subordinate males excrete more GCs than dominant males (table 1-see 'MALES-not inherited') [40,48,[56][57][58][59][60][61][62][63][64][65][66][67][68][69][70]. The opposite pattern emerges for females, where subordinate females often have greater GC production than dominant individuals, particularly when rank is not inherited rstb.royalsocietypublishing.org Phil.…”

Birth season glucocorticoids are related to the presence of infants in sifaka ( Propithecus verreauxi )

“…In mammals, on the other hand, the stress response is linked to an array of social traits, states and events that characterize individuals and their daily lives, a subset of these being reliable predictors of elevated GC levels. For example, behavioural traits such as aggression (Muller & Wrangham 2004), current states such as increased age (Sapolsky et al 1986) and reproductive status ( Fichtel et al 2007) and social context such as numbers of resident males (Gould et al 2005) and social instability (Brockman et al 2001) correlate with elevated GC responses. Likewise, demographic events such as male immigration (Alberts et al 1992), dispersal and specific events related to reproductive success such as mating (Strier et al 1999), birth of offspring (Berg & WynneEdwards 2001) and male infanticide (Engh et al 2006) have all been shown to be associated with elevated GC levels.…”