Qiviut cortisol is associated with metrics of health and other intrinsic and extrinsic factors in wild muskoxen (Ovibos moschatus)

Abstract

Glucocorticoid (GC) levels are increasingly and widely used as biomarkers of hypothalamic–pituitary–adrenal (HPA) axis activity to study the effects of environmental changes and other perturbations on wildlife individuals and populations. However, identifying the intrinsic and extrinsic factors that influence GC levels is a key step in endocrinology studies to ensure accurate interpretation of GC responses. In muskoxen, qiviut (fine woolly undercoat hair) cortisol concentration is an integrative biomarker of HPA axis activity over the course of the hair’s growth. We gathered data from 219 wild muskoxen harvested in the Canadian Arctic between October 2015 and May 2019. We examined the relationship between qiviut cortisol and various intrinsic (sex, age, body condition and incisor breakage) and extrinsic biotic factors (lungworm and gastrointestinal parasite infections and exposure to bacteria), as well as broader non-specific landscape and temporal features (geographical location, season and year). A Bayesian approach, which allows for the joint estimation of missing values in the data and model parameters estimates, was applied for the statistical analyses. The main findings include the following: (i) higher qiviut cortisol levels in males than in females; (ii) inter-annual variations; (iii) higher qiviut cortisol levels in a declining population compared to a stable population; (iv) a negative association between qiviut cortisol and marrow fat percentage; (v) a relationship between qiviut cortisol and the infection intensity of the lungworm Umingmakstrongylus pallikuukensis, which varied depending on the geographical location; and (vi) no association between qiviut cortisol and other pathogen exposure/infection intensity metrics. This study confirmed and further identified important sources of variability in qiviut cortisol levels, while providing important insights on the relationship between GC levels and pathogen exposure/infection intensity. Results support the use of qiviut cortisol as a tool to monitor temporal changes in HPA axis activity at a population level and to inform management and conservation actions.

Variation of hair cortisol in two herds of migratory caribou (Rangifer tarandus): implications for health monitoring

“…Biologically, biting insect harassment as a potential stressor is endemic to these populations, and migratory caribou may have an adaptive tolerance strategy resulting in a limited HPA axis response ( Cizauskas et al, 2015 ). A tolerance strategy hypothesis is proposed to explain the lack of association between HCC and helminth parasite infection ( Carlsson et al, 2016 ; Trevisan et al, 2017 ; Di Francesco et al, 2022 ) and may be extended to insect harassment.…”

Stress in wildlife: comparison of the stress response among domestic, captive, and free-ranging animals

“…However, the higher fecal glucocorticoid concentrations in the wild bison population (Table 1) may support the hypothesis of a more active HPA axis in wild animals. Additionally, comparison of hair (or qiviut) glucocorticoid concentrations in two related species, domestic cattle and wild muskoxen (Ovibos moschatus), also revealed higher levels in the wild population (64,83,84).…”

Technical validation and a comparison of two methods to quantify individual levels of glucocorticoids in Alpine marmot hair

“…The ability to non-invasively monitor hypothalamic-pituitary-adrenal (HPA) function as a proxy of stress in wild populations by quantifying levels of glucocorticoids (GCs), is a powerful conservation tool [18] . Non-invasive estimation of GCs is used in the wild to monitor animal welfare [55] , assess response to anthropomorphic factors [29] , monitor the ‘health’ of a population [21] , evaluate the impact of conservation management strategies [37] and make predictions pertaining to survival of wild populations facing environmental changes [49] . Although GCs can be quantified in numerous matrices the predominant media used for wild populations has been faeces [45] .…”