Fecal steroid research in the field and laboratory: improved methods for storage, transport, processing, and analysis

Since the pioneering paper "Measurement of Excreted Steroids in Macaca nemestrina" [Risler et al., American Journal of Primatology 12:91-100, 1987] was first published, field primatologists have been using fecal extraction techniques to examine adrenal and gonadal hormones. These techniques have allowed investigators to determine reproductive conditions in wild primates without causing any disruption to the populations. Over the years, many techniques have been developed to improve the ease of analysis, transportation, and purification. More of the processing can now be done in the field. This paper describes the methodology developed or adapted at the Wisconsin National Primate Research Center, and the factors involved in preparing fecal samples for steroid analysis. We provide information on the steps involved in extracting and purifying steroids from feces for measurement. The latest methods include field processing of samples, such as drying collected material or separating steroids from the fecal material by solid phase extraction (SPE). How samples are processed in the field determines the requirements for international transportation and the methods used in the laboratory. The pros and cons of the different processing methods are discussed. We also report on recent advances in laboratory quantification, with implications for steroid isolation prior to analysis. The different processes involved in isolating and measuring fecal steroids discussed here will enable investigators to understand the components necessary to ensure accurate and reliable results.