Fecal Glucocorticoids Document Stress in Female Barbary Macaques (Macaca sylvanus) Bernard Wallner,* ,1 Erich Mo¨ stl,² John Dittami,* and Hermann Prossinger‡ *Institute of Zoology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria; ²Institute of Biochemistry, University of Vienna, Josef Baumannstrasse 1, A-1221 Vienna, Austria; and ‡Institute of Human Biology, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria Accepted September 10, 1998 Patterns of received aggression and the endocrine re- sponse were related to an increase in fecal glucocorticoid metabolites in an intact semifree-ranging group of Bar- bary macaque females in order to quantify the social stress incurred over a 20-week observation period. The novel result showed that immunoreactive cortisol and 11-oxoetiocholanolone found in the feces can indeed determine the endocrine response of the adrenal gland after a social stressor. After HPLC separation of pooled fecal samples, EIA analyses using three different assays (corticosterone, cortisol, and 11-oxoetiocholanolone) to quantify immunoreactive steroids showed that the corti- costerone EIA had no distinctive immunoreactive peaks. Cortisol and 11-oxoetiocholanolone immunoassays showed respectively four and two immunoreactive sub- stances. Time series analyses revealed a behaviorally initiated increase in concentrations of cortisol and 11- oxoetiocholanolone equivalents. Furthermore, both hor- mone curves exhibit comparable time functions. Either antibody is very suitable for determining glucocorticoid secretion after periods of stress. r 1999 Academic Press Aggression is a common response when members of group-living species attempt to monopolize resources. While purposes of aggression vary, they show uniform physiological stress reactions among affected individu- als, and a physiological cascade of reactions to social hierarchies increases adrenal activity (Sapolsky, 1995). In addition to competition for access to ecological resources, sexual competition is a major motivation in the drive to dominate other members of the group (Dunbar, 1988). The metabolic effects of prolonged increases in cortisol levels lead to serious conse- quences for the organism (Thun and Schwarz, 1994): the general acute adaptation system of the organism fails and the stress response becomes destructive, producing a range of dysfunctions. Chronic stress suppresses the immune system (Peristein et al., 1993) and changes metabolic (Jayo et al., 1993) and gastroin- testinal functions (Monnikes et al., 1994). In social- living primates the effects of prolonged activation of the hypothalamo-pituitary-adrenal axis on reproduc- tive potency of individuals are well documented (Sapol- sky and Krey, 1988). Stress invoked by harassment or overt aggression represents an efficient proximate strat- egy for suppressing reproduction in subordinate indi- viduals (Dunbar, 1989); in females, ovarian function is inhibited and spontaneous abortion occurs (Wasser and Starling, 1988). Plasma cortisol concentrations are the most reliable markers of endocrine responses to social stress. Difficul- ties in collecting plasma samples and the effects of the collection procedure itself, especially under free or semifree conditions, have lead investigators to seek noninvasive approaches. The procedures for analyzing various steroids in urine and gonadal steroids in feces 1 To whom correspondence should be addressed at Institute of Zoology, Althanstrasse 14, 1090 Vienna, Austria. Fax: 143-1-31336- 778. E-mail: a8731gct@vm.univie.ac.at. General and Comparative Endocrinology 113, 80–86 (1999) Article ID gcen.1998.7183, available online at http://www.idealibrary.com on 80 0016-6480/99 $30.00 Copyright r 1999 by Academic Press All rights of reproduction in any form reserved.