Aug. 26, 2016 – American pikas – small herbivores that typically live in rocky slopes, known as talus, across many mountain ranges in the American West – are disappearing from some locations across the West due to climate change, according to a study by the U.S. Geological Survey and some of its partners.
Researchers found evidence of widespread reduction in pika range in three mountainous regions including the Great Basin, southern Utah and northeastern California. To ascertain why losses had occurred, they examined climate variables and amount of suitable habitat as predictors of pika persistence at research sites. Pikas have been dubbed an “indicator species,” which helps alert scientists to a change in the biological condition of a particular ecosystem.
“It is certainly clear that changes we have observed in pika distribution are primarily governed by climate, given that nearly all of our climate-related predictions have been borne out,” said Erik Beever, USGS research ecologist, and lead author of the study. “However, we are still refining our understanding of the exact combination of direct and indirect pathways by which climate is bringing about change.”
In 2014 and 2015, researchers surveyed over 910 locations across four states to record any pika sightings, vocalizations, and fresh food caches that they could find. Site selection was based on detection of pikas in historical surveys that occurred over roughly 100 years from the late 1890s to the early 1990s. Resurveys allow for a longer-term perspective, which is unavailable without valuable historic surveys.
In 2014 and 2015, researchers resurveyed dozens of talus patches scattered within nine sites in the Great Basin with historical records of pika presence that had not been surveyed since 1935. Pikas were not found anywhere within five of these extensive (roughly 4-mile-diameter) sites. When added to previous Basin resurveys, results indicate a >44 percent loss of pikas from sites across the Great Basin with historical records.
In Zion National Park and Cedar Breaks National Monument in southern Utah, pikas were not found at any of the locations from which they had been previously reported. Those historic evidences, obtained from museum specimens, photographs, or videos, occurred from the 1960s up through 2011 in Zion and through 2012 in Cedar Breaks. In northeastern California, pikas were not detected within 11 of the 29 historical sites. Additionally, researchers found widespread evidence that pikas existed at many places across that region in the past, but no longer occupy those areas.
Results suggest that short-term changes in pika distribution occurred in some sites due to phenomena such as drought, but other sites have not had pikas for decades. “Combined with our previous work across the western U.S., the results illustrate that pika losses are not confined solely to the Great Basin, but that the rate of decline is quite variable across the western landscape,” Beever said.
Pikas are an excellent species to study wildlife responses to climate because they can be abundant, are easily detectable and active during the day, live in identifiable habitat, and are sensitive to climate.
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In the Great Basin and southern Utah, both temperature and precipitation variables were strong predictors of pika presence, but not in northeastern California, where other studies have found habitable talus to be one of the strongest predictors of pika persistence. Even though suitable talus habitat is abundant in the Great Basin and southern Utah, climate conditions strongly appear to be limiting pika distribution in these regions.
Results suggest that losses are more pronounced in more-isolated regions of the study, and that climate outweighs the importance of habitat area in those regions. Temperature appears to be the factor most strongly influencing the pattern of pika persistence in these regions.
More-extensive surveying and monitoring will enhance the current understanding of pika distribution, especially in areas with more dramatic pika losses. Findings have added new understanding to the trend in distribution of pikas, and can assist land managers in decisions regarding conservation and management efforts. Additionally, the results add to the growing body of pika research that illustrates the nuance and variability with which climate can influence the distribution of mountain-dwelling wildlife.
The article “Pika (Ochotona princeps) losses from two isolated regions reflect temperature and water balance, but reflect habitat area in a mainland region” is published in The Journal of Mammalogy.
The study is a collaborative effort between the USGS, California Polytechnic State University, U.S. Forest Service, National Park Service, Princeton University, Montana State University, College of the Siskiyous, Bureau of Land Management, and U.S. Fish and Wildlife Service.
More information about species response to climate can found on the USGS Northern Rocky Mountain Science Center website.