Hormonal and behavioral patterns of reproduction in female hylobatids

Ovarian cyclicity, reproductive behavior, and gestation length were characterized in female hylobatids using non-invasive fecal steroid analyses and behavioral data. Progestagen metabolites were quantified in fecal samples collected for 3 months from seven females housed at seven North American zoological institutions. Mean (±SEM) ovarian cycle length was 23.1 ± 1.5 days (seven females; 22 cycles) and was similar across individuals and species (range: 15.3-27.3 days). Gestation length in white-cheeked gibbons was 191 ± 7.0 days (n = 2), and female-initiated reproductive behavior occurred throughout the ovarian cycle for each individual. This was the first study of its kind to use fecal hormone metabolite analysis in combination with behavioral observations to characterize female reproductive traits for various hylobatid species. These results contribute to our general knowledge of the basic biology of hylobatids, highlight the importance of evaluating both hormonal and behavioral information, and assist the management and breeding of zoo-housed populations of these endangered primates to support overall conservation efforts.