HUMAN DISTURBANCE AND THE PHYSIOLOGICAL RESPONSE OF ELK IN EASTERN WASHINGTON

David Jachowski,Scott Mccorquodale,Brian Washburn,Joshua Millspaugh

doi:10.2461/wbp.2015.11.3

Abstract

Stress hormone measures have proven useful for assessing effects of human disturbance on wildlife populations. However, most studies are of short duration or limited geographic scope (i.e., without spatial replication), leading to concerns about confounding effects of biotic conditions. Previous research correlated fecal glucocorticoid metabolites (FGMs) of elk (Cervus elaphus) with human disturbance, but this factor also co-varied with seasonal climatic conditions, making it difficult to make broader inference regarding the role of human disturbance. In this study we attempted to simultaneously evaluate the effects of climatic conditions and human disturbance by comparing the year-round physiological stress response of elk to varying levels of human disturbance at three study sites in south-central Washington State. FGMs were consistently elevated throughout the year at the study site receiving the greatest amount of human disturbance. We observed support for a positive effect of precipitation and increasing temperature on FGMs at the low-disturbance site, but less support for importance of climatic variables in explaining FGMs at the high-disturbance sites - suggesting that climatic variables were likely of secondary importance compared to anthropogenic stressors in elk at those sites. Collectively, while we were unable to disentangle the effects of site- specific stressors, our findings suggest that in this environment, humans were a dominant stressor influencing FGM levels. Therefore, interpreting results of physiological studies requires that researchers account for a broad combination of biotic and abiotic stressors at a particular study location. We particularly encourage future investigators to account for the potential confounding effect of human disturbance that could override other stressors.

Highlights

Human disturbance associated with road development and activity has been linked to a variety of negative effects on some wildlife, ranging from population declines and loss of genetic diversity [1, 2], to altered spatial ecology [3, 4] and physiology [5, 6, 7, 8]
Previous research correlated fecal glucocorticoid metabolites (FGMs) of elk (Cervus elaphus) with human disturbance, but this factor co-varied with seasonal climatic conditions, making it difficult to make broader inference regarding the role of human disturbance
FGMs of elk sampled at the sites receiving high human activity (Barber Flats and Yakama) were over twice as high as those sampled at the low human disturbance site (ALE) (Fig. 2)

Summary

Introduction

Human disturbance associated with road development and activity has been linked to a variety of negative effects on some wildlife, ranging from population declines and loss of genetic diversity [1, 2], to altered spatial ecology [3, 4] and physiology [5, 6, 7, 8]. The impacts of human disturbance can be difficult to monitor, and detecting negative effects such as loss of genetic diversity or population declines often requires long-term research [9]. To quantify such insidious effects on wildlife, stress hormone measures are being used as an efficient, non-invasive metric for detecting the impacts of roads and other human disturbances on wildlife physiology [8, 10, 11]. Millspaugh et al [5] observed distinct elevations in FGMs associated with road activity and high temperatures; peaks in tourism disturbance and temperatures co-occurred in the summer, making it difficult to discriminate the relative importance of tourism vs. temperature

Methods

Results

Conclusion