Document Type

Thesis

Date of Degree Completion

Summer 2019

Degree Name

Master of Science (MS)

Department

Biology

Committee Chair

Dr. Kristina A. Ernest

Second Committee Member

Dr. Alison G. Scoville

Third Committee Member

Dr. Daniel Beck

Fourth Committee Member

Dr. Jennifer L. Wilkening

Abstract

Roads often disrupt ecosystem connectivity, harming many wildlife populations. Wildlife crossing structures perforate the barrier-effect of roads, providing safe passage for species dispersing across roads, thereby reconnecting ecosystems. Some wildlife species live in modified habitats along roads and in habitat features within wildlife crossing structures, but their fitness in these potentially stressful environments is poorly understood. Chronic stress alters behavior, reduces reproduction, and has been linked to reduced survival. Animals affected by chronic stress in road-adjacent habitats could reduce the ability of wildlife crossing structures to improve connectivity across roads. I assessed stress hormone concentrations in a low-mobility species, the American Pika (Ochotona princeps), living in anthropogenic rock embankment along Interstate 90 (highway) in the Cascade Range of Washington. I extracted fecal glucocorticoid metabolite (fGCM) concentrations from fresh fecal samples to determine chronic stress levels in pikas living adjacent to the highway compared with those living in similar rock embankment in a rails-to-trails state park, and in natural rocky sites. I evaluated potential stressors in the highway and rails-to-trail habitats by measuring microclimate proxies (environmental temperatures, elevation, and longitude) and noise levels. A linear mixed-effects model was used to test for differences in fGCM concentrations among habitats and assess the potential effects of these environmental variables on stress. Pikas in the highway habitat had the lowest fGCM levels among the 3 habitats. Stress hormone concentrations showed significant relationships with longitude and noise, but not with elevation or mean daily temperatures. I hypothesize that the lowered fGCM levels of highway pikas may be a result of downregulation of the stress response under chronic exposure to stressors, potentially including highway noise. My results offer insights into the physiological response of pikas to potentially stressful environments disturbed by humans and may provide a good indicator of stress levels expected for pikas colonizing wildlife crossing structures now being constructed to improve wildlife connectivity across I90.

Available for download on Saturday, August 14, 2021

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