Data from: Long-term storage effects in steroid metabolite extracts from baboon (Papio sp.) faeces – a comparison of three commonly applied storage methods

1. The measurement of steroid hormone metabolites from faeces in wild animal populations is a powerful, non-invasive tool in behavioural endocrinology of all major vertebrate taxa. However, because such research is often done in remote areas with limited infrastructure, storage of samples for hormone analysis over long periods at high temperature is a critical issue in field endocrinology. Previous studies have indicated that storage of alcoholic faecal extracts is more reliable than storage of unprocessed faeces if no freezer is available, but a standard method has not been established yet. 2. We tested the validity of three commonly applied storage conditions - liquid extracts, dried extracts, and extracts placed on solid phase extraction (SPE)-cartridges - to preserve concentrations of glucocorticoid and androgen metabolites from faecal extracts of olive baboons (Papio anubis) at high temperature over one year. 3. Temporal variation in concentrations was detected for all metabolites and all storage conditions, including values measured from the control condition, i.e. extracts stored at 20°C. This suggested that most variation was due to inter-assay variability, corroborated by comparisons of variation in ‘quality controls’ and samples. 4. Compared to frozen control samples, liquid extracts were stable for up to 24 weeks, extracts on SPE-cartridges were stable for up to 50 weeks, while steroid metabolite concentrations in dried extracts decreased slightly over time. 5. If steroid samples have to be stored at ambient temperature, we suggest storage of liquid extracts for up to 24 weeks in a dark and cool place. For longer periods, SPE-cartridges should be applied as evaporation, a potential confound arising with long-term storage of liquid extracts at higher temperatures, is not a problem in this storage condition. Storage of dried extracts is more cost-effective, but may result in small time-dependent changes in steroid concentrations.

1. 针对所有主要脊椎动物类群的行为内分泌学（behavioural endocrinology）研究而言，从野生动物种群粪便中检测类固醇激素代谢物（steroid hormone metabolites），是一种高效且无创的研究手段。然而此类研究多在基础设施匮乏的偏远地区开展，因此高温下长期储存样本用于激素分析，是野外内分泌学研究面临的关键难题。既往研究表明，若无冷冻条件可用，酒精粪便提取物的储存效果优于未处理粪便样本，但目前尚未形成标准化的储存方法。
2. 本研究针对橄榄狒狒（Papio anubis）粪便提取物中的糖皮质激素（glucocorticoid）与雄激素（androgen）代谢物，对三种常用储存条件的有效性开展了为期一年的高温稳定性测试，三种储存条件分别为：液体提取物、干燥提取物以及置于固相萃取（SPE）小柱上的提取物。
3. 所有代谢物与所有储存条件下均检测到浓度随时间的变异，包括储存于-20℃的对照组样本，这一结果提示大部分变异源于批间变异（inter-assay variability），该结论通过对比“质量控制样本”与实际样本的变异程度得到了验证。
4. 与冷冻对照组样本相比，液体提取物可稳定保存长达24周，置于固相萃取（SPE）小柱上的提取物稳定保存时长可达50周，而干燥提取物中的类固醇激素代谢物浓度则随时间出现小幅下降。
5. 若类固醇样本需在环境温度下储存，我们建议将液体提取物置于避光阴凉处，最长可保存24周；若需更长储存时长，则应采用固相萃取（SPE）小柱储存方式——该条件不会出现液体提取物高温长期储存时可能产生的蒸发混淆因素。干燥提取物储存成本更低，但可能导致类固醇浓度出现小幅的时间依赖性变化。