Quantifying Long-Term Stress in Brown Bears with Hair Cortisol Concentration: A Biomarker That May Be Confounded by Rapid Changes in Response to Capture and Handling

The study examined hair cortisol concentration (HCC) as a biomarker for long-term stress in brown bears, using 505 hair samples from 486 bears in Alberta, Canada. It found that HCC was influenced by both long-term stressors, such as nutritional stress indicated by an inverse relationship with body condition, and short-term stressors from capture and handling. Capture methods like helicopter, leg-hold snare, and culvert trap significantly elevated HCC, challenging the assumption that HCC is solely determined by passive diffusion from blood. The study concluded that while HCC is a useful stress biomarker, its interpretation must consider potential confounding factors from capture-related stress, highlighting the need for further validation and research.