For statistical analysis the SPSS statistics package (version 19.0; IBM SPSS, Armonk, NY, USA) was used. The distribution of our **data** indicated that fGC **data** were normally distributed after Kolmogorov-Smirnov; therefore, we used untransformed fGC values for graphical representation of the data. In addition, means were tested for significant differences with the t-test for repeated and independent samples, and comparisons between groups for zoo location, seasons, social group and age class were analysed by one-way analysis of variance (ANOVA). In the case of overall significant effects, when appropriate, post hoc comparisons were conducted by Tukey, Wilcoxon signed-rank, and Kruskall-Wallis tests. For all statistical tests, the alpha value was set at P = 0.05. Assays results are expressed as mean ± standard error of mean ng metabolite concentrations of fGC per dry gram of faeces. To determine correlations between fGC levels and social rank, Spearman correlation analysis was used.