October 2025 in “Journal of Veterinary Diagnostic Investigation” Black hair in cats has higher cortisol levels than white hair.
199 citations
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July 2007 in “General and Comparative Endocrinology” Hair cortisol can reliably indicate chronic stress in cats and dogs.
69 citations
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May 2016 in “General and Comparative Endocrinology” External factors can significantly affect hair cortisol levels, so it's not always a reliable stress marker.
December 2025 in “Biology Bulletin Reviews” Hair cortisol can indicate animal stress but varies with many factors.
10 citations
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September 2019 in “Frontiers in Veterinary Science” Older steers have higher hair cortisol levels than younger steers.