Non-invasive techniques for analysing hormonal indicators of stress.

The growing concern over animal welfare has led to an increased awareness of the need to monitor and reduce stress in laboratory, zoo, and farm animals. To do so, valid and reliable methods are necessary. In the present work, we discuss non-invasive techniques for analysing hormonal indicators of stress, particularly glucocorticoids. Specifically, we describe methods for analysing samples of saliva, urine, and faeces, the collection of which, unlike blood sampling, does not represent a source of stress and thus a potential source of bias. We also address species-specific responses to stress and inter-individual variability, the reliability of specific hormonal assays, and the use of indirect measures of circulating stress hormones.