Exposure to environmental stressors can activate an individual’s hypothalamic–pituitary–adrenal axis in a cascading process that releases glucocorticoid steroids ( Wingfield, 2013). Our findings provide a baseline to support the development of non-invasive physiological monitoring for assessing environmental impacts on moose populations.Ĭhanging landscape conditions can exert pressures on wildlife populations, which are detrimental to the health and fitness of individuals ( Angelier and Wingfield, 2013). Our results provide novel evidence linking moose calf stress and nutrition, a problematic parasite and challenging environment and winter survival. By late March, as winter ticks are having their greatest toll and endogenous resources become depleted, we estimated a curvilinear relationship between fGCM concentrations and survival. Our predictive models estimated that winter survival was negatively related to UN:C ratios and positively related to fGCM concentrations, particularly in early winter. Calf UN:C ratios also increased in individuals with home ranges composed of little deciduous forests during adult winter tick engorgement. Calf UN:C ratios increased in calves with lighter weights and higher tick loads in early winter. Calf fGCM concentrations increased with nutritional restriction and snow depth during adult winter tick engorgement.
We then used these physiological data to build generalized linear models to predict calf winter survival. We used generalized mixed-effects models to evaluate the influence of individual condition, winter ticks, habitat, climate and human development on stress and nutrition in calf moose. We collected 407 fecal and 461 snow urine samples from 84 radio-collared moose calves in the winters of 2017–2019 (January–April) to measure fecal glucocorticoid metabolites (fGCM) concentrations and urea nitrogen:creatinine (UN:C) ratios.
We examined the influence of several environmental factors on moose calf stress hormone metabolite concentrations and nutritional restriction in Vermont, USA. Research efforts have focused on the effects of winter tick infestation on moose survival and reproduction, but stress and nutritional responses to ticks and other stressors remain understudied. Moose populations in the northeastern United States have declined over the past 15 years, primarily due to the impacts of winter ticks.