Relating sub-surface ice features to physiological stress in a climate sensitive mammal, the American pika (Ochotona princeps).

Jennifer L Wilkening,Chris Ray,Johanna Varner,Gil Bohrer

doi:10.1371/journal.pone.0119327

Jennifer L Wilkening, Chris Ray + Show 2 more

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https://doi.org/10.1371/journal.pone.0119327

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Abstract

The American pika (Ochotona princeps) is considered a sentinel species for detecting ecological effects of climate change. Pikas are declining within a large portion of their range, and ongoing research suggests loss of sub-surface ice as a mechanism. However, no studies have demonstrated physiological responses of pikas to sub-surface ice features. Here we present the first analysis of physiological stress in pikas living in and adjacent to habitats underlain by ice. Fresh fecal samples were collected non-invasively from two adjacent sites in the Rocky Mountains (one with sub-surface ice and one without) and analyzed for glucocorticoid metabolites (GCM). We also measured sub-surface microclimates in each habitat. Results indicate lower GCM concentration in sites with sub-surface ice, suggesting that pikas are less stressed in favorable microclimates resulting from sub-surface ice features. GCM response was well predicted by habitat characteristics associated with sub-surface ice features, such as lower mean summer temperatures. These results suggest that pikas inhabiting areas without sub-surface ice features are experiencing higher levels of physiological stress and may be more susceptible to changing climates. Although post-deposition environmental effects can confound analyses based on fecal GCM, we found no evidence for such effects in this study. Sub-surface ice features are key to water cycling and storage and will likely represent an increasingly important component of water resources in a warming climate. Fecal samples collected from additional watersheds as part of current pika monitoring programs could be used to further characterize relationships between pika stress and sub-surface ice features.

Highlights

Climate change in the form of rising temperatures, changing precipitation patterns and increased frequency of extreme weather events is occurring at an unprecedented rate [1]
If habitats underlain by ice promote pika health, we hypothesized that glucocorticoid metabolites (GCM) concentration would be lower in samples collected from within rock-ice features (RIFs). To further characterize this relationship, we modeled GCM concentrations in pika scat as a function of microclimatic conditions measured in situ over the previous two years
This research was conducted in the US Rocky Mountains at five study sites: Niwot Ridge Long Term Ecological Research Site (NWT), Green Lakes Valley Watershed (GLVW), Brainard Lake Recreation Area (BLRA), and Rocky Mountain National Park (RMNP) in Colorado, and Emerald Lake (EL) in Montana (Table 1)

Summary

Introduction

Climate change in the form of rising temperatures, changing precipitation patterns and increased frequency of extreme weather events is occurring at an unprecedented rate [1]. Increased atmospheric CO2 has resulted in changes in plant productivity and plantherbivore interactions [5], [6]. Much of the world’s human population depends on water resources that originate in alpine ecosystems, and up to 80% of the planet’s fresh surface water comes from high elevation watersheds [7]. These mountainous and highland regions are often referred to as the world’s natural “water towers”, and evidence suggests that warming may occur more rapidly at these higher elevation locations [8]-[11]. Similar declines around the world will have far reaching consequences for both humans and wildlife [1]

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