New study documents population declines in Great Basin
U.S. Geological Survey scientists have filled in another piece in the pika puzzle, finding that changes in distribution of populations of the tiny mammals are mainly influenced by climatic factors. The new study, published in The Journal of Mammalogy, helps show how global warming will affect the species.
Several previous research efforts have been inconclusive, and one study from Colorado suggests that pikas are holding their own in the highest reaches of the central and southern Rocky Mountains. But the new study, conducted in 2014 and 2015 at 910 sites, showed widespread reduction in pika range in three mountainous regions including the Great Basin, southern Utah and northeastern California.
Another recent study that included National Park Service researchers tried to project where pikas will be able to persist in places like Rocky Mountain National Park, Crater Lake and Yellowstone National Park. More information is available on the NPS Pikas in Peril website.
A 2012 study in the Great Basin found that pikas living in lower elevations are moved uphill 11 times faster during the past decade than during the 20th century, suggesting their habitat is rapidly dwindling. That study also found some pika populations may be able to hang on by using non-traditional habitats at the edge of their climatic niche.
Pikas are considered a bellwether species for global warming impacts in the alpine zones because they have a fairly narrow range of habitat, based on temperatures and the availability of food and cover.
In a press release, USGS researchers said they compared their findings with historical surveys made between the late 1890s and the early 1990s. Their new surveys showed that pikas had vanished from several areas, including five of nine sites in the mountains of the Great Basin, the mountainous basin-and-range territory extending from eastern California to central Utah.
In that region, pikes live in discontiguous patches of habitat on so-called sky islands, where the populations are genetically and geographically isolated from one another.
The species has apparently vanished completely from some sites in Zion National Park and Cedar Breaks National Monument in southern Utah, where they had been documented as recently as 2011 and 2012.
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.
The study found that short-term changes, including drought, are a factor in pika distribution, but that long-term global warming is also in play.
“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,” said USGS biologist Erik Beever.
The study found that temperature and precipitation were strong predictors of pika presence in the Great Basin and southern Utah, but less important in California, where the presence of habitable talus was more important.
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.
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 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.