An evaluation of hair cortisol concentration as a potential biomarker of long-term stress in free-ranging grizzly bears (Ursus arctos), polar bears (Ursus maritimus), and caribou (Rangifer tarandus sp.)
Human-caused ecological change negatively affects the sustainability of many wildlife populations but may be especially challenging for large carnivores and ungulates. Long-term physiological stress may be an important mechanism linking ecological change with impaired health and reduced population performance in these groups. The determination of hair cortisol concentration (HCC) has recently demonstrated potential as a biomarker of long-term stress in humans and domestic animals, and may also represent a practical technique for use in free-ranging wildlife. The objectives of this research program were to: 1) develop and apply an accurate and reliable method for measuring cortisol levels in hair collected opportunistically or remotely from free-ranging grizzly bears (Ursus arctos), polar bears (Ursus maritimus), and caribou (Rangifer tarandus sp.), and 2) to evaluate the utility of HCC as a biomarker of long-term stress (and thus potentially useful conservation tool) in these threatened species. An enzyme-immunoassay (EIA) based technique for measuring HCC in non-human primates was successfully modified for use with small quantities (5-100 mg) of hair representative of samples which may be obtained through opportunistic (e.g. hunting, research captures, archives) or remote (e.g. barb wire snagging) methods in each species. HCC was determined in 151 free-ranging grizzly bears from Alberta, Canada (mean 2.84 pg/mg, range 0.62-43.33 pg/mg); 185 free-ranging polar bears from southern Hudson Bay, Canada (mean 0.48 pg/mg range, 0.16-2.26 pg/mg); in 12 captive Alaskan caribou (R. t. granti) (mean 2.31 pg/mg, range, 1.57-3.86 pg/mg) and 12 captive reindeer (R .t. tarandus) (mean 2.88 pg/mg, range 2.21-3.40 pg/mg) injected either with adrenocorticotropic hormone (ACTH) or saline; and in 94 free-ranging caribou (R. t. groenlandicus) from West Greenland (mean 2.21 pg/mg, range 0.60-6.90 pg/mg). Factors influencing HCC in each species were then explored including: 1) technical considerations for the prudent use of HCC analysis and 2) potential relationships between HCC, biological traits, health, and prevailing environmental conditions. Evidence revealed in this study suggests that, with further research, this technique may show potential as a practical conservation tool for use in free-ranging grizzly bear, polar bear, and caribou populations.
hair cortisol concentration, long-term stress, grizzly bear, Ursus arctos, polar bear, Ursus maritimus, caribou, reindeer, Rangifer tarandus, ecological change, health
Doctor of Philosophy (Ph.D.)
Western College of Veterinary Medicine
Veterinary Biomedical Sciences