The primary objective of this investigation is to develop, validate and apply the determination of cortisol, a stress related hormone, in hair as a sensitive, reliable and non-invasive measure of long term stress in caribou. Because cortisol is deposited within the hair shaft while the hair is growing (many weeks to months), hair represents a potentially superior indicator of long-term stress in comparison to other matricies (e.g. blood, urine, saliva and feces) in which cortisol levels represent stress over hours to days. In addition, hair can be collected non-invasively from live captured animals or opportunistically from animals killed during hunting activities. Hair can also be transported and stored at ambient temperature and molecules incorporated into hair may remain detectable for extended periods (from years to centuries).