Validation of a field-friendly extraction and storage method to monitor fecal steroid metabolites in wild orangutans
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Measuring hormone metabolites from feces is the most often used method to assess hormonal status in wildlife. Although immediate freezing of fecal samples collected in the field is the best method to minimize the risk of degradation of hormones over time, this is often not possible in remote field sites. Therefore, alternative storage and preservation methods for fecal samples are required in these conditions. We conducted an experiment to investigate if fecal glucocorticoid (FGCM) and progesterone metabolite (pregnanediol-3-glucuronide; PdG) levels measured from samples that were extracted with a simple, field-friendly methodology correlate with those generated from frozen samples. We also evaluated whether storing fecal samples in alcohol is a suitable alternative to preserve FGCM and PdG concentrations long-term (i.e. over a 9-month period) at locations where fecal extraction is not feasible. Finally, we tested if the hormone concentrations in unpreserved fecal samples of orangutans change over 14 h when stored at ambient conditions, representing the maximum duration between sample collection and return to the camp. FGCM and PdG levels measured from samples that were extracted with the field-friendly method showed strong correlations with those generated from frozen samples, and mean levels did not differ significantly between these methods. FGCM concentrations showed no significant change compared to control samples when fecal samples were stored for up to 6 months in alcohol at ambient temperature and PdG concentrations even remained stable for up to 9 months of storage. FGCM concentrations of fecal samples kept at ambient temperature for up to 14 h post-defecation did not significantly differ compared to control samples frozen immediately after collection. These results provide the basis for the successful monitoring of the physiological status of orangutans living in remote natural settings, like those included in the Indonesian reintroduction programs.
KeywordsPongo spp. Fecal glucocorticoids PdG Sample storage Hormone degradation
This study was part of the project Building Indonesia’s Research Capacity for Orangutan Conservation Biology (joint research project IZ70Z0_131309) and funded by the program Research Partnerships with Developing Countries, a joint initiative of the Swiss National Science Foundation and the Swiss Agency for Development and Cooperation. Further generous funding was provided by the A.H. Schultz Foundation and the Claraz Foundation. All applicable international, national and/or institutional guidelines for the care and use of animals were followed. The authors have no conflicts of interest to declare. We thank the orangutan keepers, vet and staff at Batu Mbelin Orangutan Care Centre and Ragunan Zoo for their help in collecting samples for this study. We also thank Dr. Ian Singleton from SOCP and YEL for giving us permission to collect samples, drh. Ricko Lany Jaya and drh. Yenny Saraswati for their help during sample collection in Medan, and Andrea Heistermann for her expert help during hormone training in Göttingen. We are also grateful to Keith Hodges and the German Primate Centre as well as the University of Zurich for their long-standing support of the endocrinology lab at the Faculty of Veterinary Medicine, Bogor Agricultural University.
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