Data from: Fecal cortisol metabolites to assess stress in wildlife: evaluation of a field method in free ranging chamois

1. Non-invasive faecal cortisol metabolite (FCM) analysis is a
well-established tool to quantify stress in captive and free-ranging
species. While the method has great potential, its suitability in field
studies might be limited when faecal samples from unknown individuals are
used. Possible factors affecting final results and thus jeopardizing
correct data interpretation are individual and sex-specific variation,
storage conditions and uneven distribution of metabolites in the faeces.
2. We tested these factors on a population of free-ranging Alpine chamois
Rupicapra rupicapra rupicapra in the Austrian Alps. Faecal samples (n =
183) were analysed with an established enzyme immunoassay (EIA). To
further validate the assay for FCM in chamois, a high-performance liquid
chromatography (HPLC) was performed. Sex-specific differences in
metabolite excretion were evaluated. Effects of storage length and
temperature on FCM were tested with two experiments. The distribution of
metabolites in the faeces was determined by the analysis of subsamples of
single faecal samples. Potential individual effects on FCM levels and
individually variable reactions to stressful events were evaluated with a
simulation experiment. 3. Patterns of immunoreactive peaks after HPLC
separation were similar for different faecal samples, except in one sample
of a male. In the stability tests, storage time at ambient temperature
prior to freezing and the individual were the most important variables in
modulating FCM. Concentrations within single samples varied significantly
between pellets. Analysis of faecal samples collected from June to October
showed a highly significant seasonal trend (P < 0·001) and a
considerable variance of FCM levels within the population. Simulations
confirmed that individual reactions to stressors in terms of varying
gradients and FCM levels can explain the observed FCM patterns. 4. Using
FCM to assess adrenocortical function requires measuring extensively
metabolized products of glucocorticoids, whose excretion and detection in
faeces depend on several environmental, endogenous and methodological
factors. In free-ranging wildlife, these factors and the intrinsic
individual differences in FCM excretion generate systemic noise and
substantially distort final results. Therefore, sampling of unknown
individuals inevitably jeopardizes meaningful interpretation of data, if
the above named factors are not taken into consideration.