While American pika populations across the northwestern United States have been disappearing as temperatures rise, data from an unpublished study show that pikas in Glacier National Park do not follow the trend.
The furry 4-to-6-ounce rabbit relatives can survive cold climates because they have a thick coat and a high metabolism, which maintains their body temperature. These adaptations, however, can be disadvantageous in warmer months. When their body temperature breaks 109 degrees, pikas often experience potentially fatal stress levels.
On hot days they take refuge under the talus, or fields of large rocks, and forgo food. A sustained heat wave may inhibit their ability to store enough food for the winter.
Pikas do not hibernate, instead relying on the snow for insulation. A low snowpack makes this difficult, and an early melt disrupts their reproductive patterns.
For these reasons, “[pikas] are the canary in the coal mine for climate change,” said Mackenzie Jeffress, a pika researcher, in a 2013 video for Pikas in Peril, a project surveying pika populations across two national monuments and six national parks, of which Glacier is not included. “They are an indicator of climate change because they are temperature-sensitive.”
Pika occupancy decreases at sites where average temperatures increase and remain high; the native pikas either abandon the site or perish there. A long-term shift in habitat preference demonstrates this vulnerability. Thousands of years ago, pikas lived in valley bottoms. Now, they primarily occupy colder, higher-elevation alpine areas.
There is a particularly strong correlation between population presence in temperature in Nevada and California. As yearly low temperatures in the United States have risen annually in the last half-decade, 28 percent of documented pika populations in the Great Basin have gone extinct within the past 30-80 years.
The connection is weaker in Colorado and Montana.
Northwestern Montana’s average temperatures have risen by 2.34 degrees in the last century, which is 1.8 times the national average, and warming typically occurs faster at the higher elevations where pikas have migrated.
Data from a 2008-2010 study led by Lucas Moyer-Horner, of the University of Utah, show that, so far, Glacier’s pikas are unaffected by these temperature increases, or at least the effects of climate change on its populations are unlike what has been observed elsewhere.
After surveying over 1,000 sites, Moyer-Horner estimates that there are between 5,040 and 9,860 pikas in the national park. While the study was too short to demonstrate population stability, he found that there is no strong correlation between which talus sites pikas occupy in Glacier and the sites’ temperatures, elevations, or aspects.
“We found them at the lowest elevations, along Going-to-the-Sun-Road, as well as at the tops of the tallest peaks,” Moyer-Horner said.
The little mammals also showed no preference for north- or south-facing talus sites.
“So,” he continued, “they’re occupying the entire range at this point.”
From 2012 to 2014, Elizabeth Flesch of the Crown of the Continent Research Center and volunteer citizen scientists surveyed 45 pika sites in the park. Of the five lowest sites, located between 4,500 and 5,000 feet, three remained occupied during the course of their monitoring, one remained unoccupied, and only one that had been occupied in 2012 was found abandoned in 2014. These results affirm that Glacier’s pikas aren’t yet fleeing en masse from the lowest elevations.
Moyer-Horner says that he doesn’t know why this is the case.
“We found that body size and fur properties are the determining factors for pikas overheating,” Moyer-Herner said, so it’s possible that the park’s pikas might have adapted to a more diverse range of habitats than the pikas in California or Nevada. Moyer-Herner suggested that they might have shorter fur or smaller body size.
The park’s geographic location and cool climate is another likely factor. The impact of climate change on low elevation sites might be less significant in Glacier than it has been in regions further south.
Accordingly, Moyer-Horner predicts that Glacier’s pikas will be among the last in the United States to experience population constriction associated with climate change.
“In that way,” he said, “Glacier may be a critical refuge for the species as global temperatures continue to rise during the next 50-100 years.”
It also means that Glacier’s pikas could be among the last canaries to call, their cry a final warning of impending climate change.