Cortisol concentrations in hair are used increasingly as a biomarker of long-term stress in free-ranging wildlife. However, methodological differences between studies that include e.g. the measurement of cortisol in only the hair shaft (i.e. follicle absent, as with shaved hair) versus the whole hair (i.e. follicle present, as with plucked hair), often make comparison across studies impossible. We conducted an experiment, in which we compared cortisol concentrations in paired subsamples of hair with and without follicles from 30 free-ranging Scandinavian brown bears. Observed cortisol values were significantly greater in samples with follicles present. The effect of follicles remained significant also with sex and age of sampled bears taken into account. Unification of the methods of hair collection and preparation, will allow for valid comparisons, and to optimize labour input in ecophysiological studies.
In this study we cooperated with Toxicology Centre of the University of Saskatchewan in Saskatoon (Canada), RGL Recovery Wildlife Health & Veterinary Services, Department of Veterinary Biomedical Sciences of the University of Saskatchewan, the Faculty of Environmental Science and Natural Resource Management of the Norwegian University of Life Sciences and the Department of Natural Sciences and Environmental Health of the University of South-Eastern Norway.
You can read the paper here https://academic.oup.com/conphys/article/8/1/coaa003/5719526