Evaluation of hair cortisol concentration as a biomarker of long‐term stress in free‐ranging polar bears

Abstract

Long-term physiological stress in individual animals may be an important mechanism linking ecological change with impaired wildlife population health. In the Southern Hudson Bay (SH) subpopulation of polar bears (Ursus maritimus), increasing stress associated with climate warming may be related to declining body condition. Accordingly, the development of tools to assess long-term stress in this species may prove invaluable for conservation efforts in this threatened population. The measurement of hair cortisol concentration (HCC) has shown promise as a potential biomarker of long-term stress in free-ranging bears. However, to serve as a useful management tool, factors influencing HCC in polar bears must be identified and then revealed to establish linkages between environmental conditions and the fitness of individual animals. We determined HCC (median ¼ 0.48 pg/mg [range ¼ 0.16-2.26 pg/mg]) in 185 polar bears captured in southern Hudson Bay from 2007 to 2009. HCC was influenced by sex, family group status, and capture period but not by body region or hair type. Using models developed through a combination of hypothesis testing and information theory, we also determined that HCC was negatively associated with growth indices (length, mass, and body condition index) linked to fitness in polar bears. Additional research will be required across several polar bear populations to establish the utility of HCC as a tool for polar bear conservation. ß 2012 The Wildlife Society.

Cortisol levels in beluga whales (Delphinapterus leucas): Setting a benchmark for Marine Protected Area monitoring

“…Findings suggest that age has an underlying influence on benchmark cortisol levels. In polar bears, sex, size, and life-stage interactions were important factors in defining hair cortisol levels, reflecting the various influences of reproductive stress and energetic demands of growth, fasting, and migration (Macbeth et al 2012). These findings lend support to age being an important confounding variable influencing cortisol levels.…”

“…Differences were noted between sexes only for the innermost blubber layer; however, the small sample size for females precludes a complete assessment of the influence of sex on cortisol. Results in the literature regarding sex differences in cortisol are mixed in marine and terrestrial mammals, with some documenting differences among sexes in polar bears (Oskam et al 2004;Macbeth et al 2012) whereas others found no differences in polar bears, grizzly bears, and harbour porpoises (Eskesen et al 2009;Macbeth et al 2010;Bechshoft et al 2013). The higher cortisol levels in the metabolically active inner blubber layer of females compared to males may be a reflection of higher stress conditions or energetic demands in reproductive females (Macbeth et al 2012 and references therein).…”

“…Results in the literature regarding sex differences in cortisol are mixed in marine and terrestrial mammals, with some documenting differences among sexes in polar bears (Oskam et al 2004;Macbeth et al 2012) whereas others found no differences in polar bears, grizzly bears, and harbour porpoises (Eskesen et al 2009;Macbeth et al 2010;Bechshoft et al 2013). The higher cortisol levels in the metabolically active inner blubber layer of females compared to males may be a reflection of higher stress conditions or energetic demands in reproductive females (Macbeth et al 2012 and references therein). The timing of the beluga hunt (typically July) corresponds with the calving season, and with a 14 month gestation period, females are either in an early phase of gestation or have just entered post-partum phases, as such hunters typically avoid hunting female belugas (Harwood et al 2002).…”

“…Cortisol has been used as an indicator of stress response and overall population health for a wide range of mammals (Sheriff et al 2011;Atkinson et al 2015). It has been quantified in many matrices such as blood (serum/plasma), urine, feces and hair, as well as in blubber and the blow from cetaceans (St. Aubin et al 2001;Schmitt et al 2010;Macbeth et al 2012;Palme et al 2013;Thompson et al 2014;Kellar et al 2015;Trana et al 2015). Cortisol has also provided insight into stress associated with contaminants, such as persistent organic pollutants (POPs) that include PCBs and PBDEs (Verboven et al 2010;Bechshoft et al 2012b).…”

Hair cortisol detection in dairy cattle by using EIA: protocol validation and correlation with faecal cortisol metabolites

“…This is due to the hair growth physiology, hair vascularisation and hormone accumulation mechanisms that are associated (Koren et al, 2002;Gow et al, 2010;Stalder and Kirschbaum, 2012). No other matrix seems to have the same potential to evaluate long-term hypothalamic-pituitaryadrenal (HPA) axis activity and thereby, long-term or chronic stress (Van Uum et al, 2008;Macbeth et al, 2012;Russell et al, 2012). In spite of the clear advantages and potential applications of hair cortisol detection, several gaps need to be clarified, especially regarding the origin of the cortisol and the factors that modulate its accumulation.…”