Noninvasive measures of physiological stress are confounded by exposure

Diana J R Lafferty; Marketa Zimova; Lindsay Clontz; Klaus Hackländer; L Scott Mills

doi:10.1038/s41598-019-55715-5

Noninvasive measures of physiological stress are confounded by exposure

Sci Rep. 2019 Dec 16;9(1):19170. doi: 10.1038/s41598-019-55715-5.

Authors

Diana J R Lafferty^{1

2

3}, Marketa Zimova^{4

5}, Lindsay Clontz⁶, Klaus Hackländer⁷, L Scott Mills^{4

8}

Affiliations

¹ Wildlife Ecology and Conservation Science Lab, Department of Biology, Northern Michigan University, Marquette, MI, 49855, USA. [email protected].
² Fisheries, Wildlife, and Conservation Biology Program, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, 27695, USA. [email protected].
³ Wildlife Biology Program, University of Montana, Missoula, MT, 59812, USA. [email protected].
⁴ Wildlife Biology Program, University of Montana, Missoula, MT, 59812, USA.
⁵ School for Environment and Sustainability, Institute for Global Change Biology, University of Michigan, Ann Arbor, MI, 48104, USA.
⁶ Fisheries, Wildlife, and Conservation Biology Program, Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC, 27695, USA.
⁷ Institute of Wildlife Biology and Game Management, University of Natural Resources and Life Sciences, Vienna, Gregor-Mendel-Str. 33, 1180, Vienna, Austria.
⁸ Office of Research and Creative Scholarship, University of Montana, Missoula, MT, 59812, USA.

Abstract

Glucocorticoids and glucocorticoid metabolites are increasingly used to index physiological stress in wildlife. Although feces is often abundant and can be collected noninvasively, exposure to biotic and abiotic elements may influence fecal glucocorticoid metabolite (FGM) concentrations, leading to inaccurate conclusions regarding wildlife physiological stress. Using captive snowshoe hares (Lepus americanus) and simulated environmental conditions, we evaluated how different realistic field conditions and temporal sampling constraints might influence FGM concentrations using an 11-oxoetiocholanolone-enzyme immunoassay. We quantified how fecal pellet age (i.e., 0-6 days), variable summer temperatures, and precipitation affected FGM concentrations. Fecal pellet age had a strong effect on FGM concentrations (β_Age = 0.395, s.d. = 0.085; β²_Age = -0.061, s.d. = 0.012), which were lowest at the beginning and end of our exposure period (e.g., mean_day6 = 37.7 ng/mg) and typically highest in the middle (mean_day3 = 51.8 ng/mg). The effect of fecal pellet age on FGM concentrations varied across treatments with warm-dry and cool-wet conditions resulting in more variable FGM concentrations relative to control samples. Given the confounding effects of exposure and environmental conditions, if fresh fecal pellet collection is not an option, we encourage researchers to develop a temporally consistent sampling protocol to ensure all samples are exposed to similar environmental conditions.

Publication types

Research Support, Non-U.S. Gov't
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animals
Confounding Factors, Epidemiologic
Environmental Exposure*
Feces / chemistry
Female
Glucocorticoids / metabolism
Hares / physiology*
Male
Metabolome
Models, Biological
Stress, Physiological*

Substances

Glucocorticoids