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Is The American Pika Really On The Road To Extinction Due to Climate Change?
How accurate is the distribution of the American pika as an indicator of climate change? Darting about slopes of talus in the upper reaches of Western national parks, these six-inch-long cousins to rabbits have been portrayed by groups from the World Wildlife Fund to the Endangered Species Coalition as the forward scouts on the road to extinction due to a warming world.
Much of the concern for pikas stems from long-running research in the Great Basin that indicates warming temperatures are squeezing pikas up and out of their alpine haunts. However, a just-released study suggests that the diminutive mammals with the big ears and distinctive call are more widespread than thought in some areas of their geographic distribution and seem to be thriving in a temperature range greater than long assumed possible.
The research, by Dr. Constance Millar and Dr. Robert Westfall in the U.S. Forest Service's Pacific Southwest Research Station, seems to smudge, at least, the poster-child status the pika has been given by groups and organizations concerned about how a warming climate would impact wildlife across North America.
Last year the Natural Resources Defense Council and the Rocky Mountain Climate Organization cited the perceived plight of the pika in their report, National Parks in Peril, The Threats of Climate Disruption.
Pikas, which look like hamsters but are more closely related to rabbits, are mountaintop residents unusually sensitive to high temperatures, making them candidates as “early sentinels” to a changed climate. Researchers recently surveying 25 sites in the Great Basin (between the Rocky Mountains and the Sierra Nevada) known to have previously had pika populations failed to find any pikas in nine sites—primarily those at lower, hotter elevations, wrote the groups. This raises concerns for the future of the species as the climate continues getting hotter. The risks to pikas could be greater in the lower-elevation areas where they occur, such as Bandelier and Lava Beds (in California) national monuments, Craters of the Moon National Monument and Preserve (in Idaho), and Zion National Park.
And in February the Center for Biological Diversity criticized the Obama administration for refusing to provide Endangered Species Act protection for the pika, saying there's ample evidence that the species is in danger of becoming extinct by the end of the century due to warming temperatures.
That determination was based in part on the research by Drs. Millar and Westfall, who have identified roughly 500 sites in portions of the High Sierra, southwestern and central Great Basin, and central Oregon Cascades where they could identify "recent" pika presence. Their research notes that some 12 percent of these sites are at elevations nearly 1,700 feet lower than historical records have set as the borderline for pikas.
The conflicting studies, as well as other pika research and observations, seem to signal a need for more extensive field work to better gauge not only exactly how a warming climate could affect pikas but to more definitively map their current populations.
Pikas, due to the thick coats they grow to insulate themselves against the cold winters in the higher elevations of the Rocky, Sierra Nevada, and Cascade ranges, prefer their summer climates cool and moist. You can often see or hear them in the high country of Grand Teton, Rocky Mountain, Yellowstone, Glacier and Yosemite national parks, where they reside in talus fields so they can escape the mid-day sun in summer, and predators, by darting underground into cooler sanctuaries.
Throughout the growing seasons these tireless animals stockpile "haypiles" of vegetation to help get them through the long winters. Territorial in nature, pikas hold reign over home ranges of only about 50 meters. Within this zone they stash their haypiles, rear a litter, sometimes two, of offspring a year, and live to maybe 7 years in age.
Some conservation groups fear pikas will literally run out of elevation to stay cool. Long cited by these groups as evidence that a warming climate is slowly but steadily squeezing pikas toward extinction is the research Dr. Erik Beever produced from surveys in the Great Basin, the area between the Sierra Nevada and Rocky Mountain ranges that drains internally. Dr. Beever, a wildlife ecologist, based his work on revisiting 25 sites with historical records of pikas in the basin. His field work in the 1990s and early 2000s collectively noted that pikas have been lost from nine of the 25 sites in the 55-86 years since their last recorded presence, and at sites that retained pikas, the lower limit of pikas was moving higher in elevation.
At the same time, the research by Drs. Millar and Westfall could be cited as evidence that these tiny animals can tolerate more extremes than some think. Their work, published in the February issue of Arctic, Antarctic and Alpine Research (and attached below), points to thriving pika populations in the areas they've surveyed in recent years.
In addition to their findings, Dr. Beever himself in 2005 found a "robust" pika population at one site in the Great Basin where in the 1990s the species was detected but considered to be "functionally extirpated." This incorrect classification he attributes to not initially being able to either survey the site during optimal hours of the day or to re-visit the site, both of which he did for all other extirpated sites in both the 1990s and 2000s.
Dr. Beever has also found populations in the structurally complex formations at Lava Beds National Monument some 800 meters below where they would be expected to be found (given distributional relationships evident in the Great Basin), and notes that a previously unknown population was found in northwestern Nevada in 2002. That discovery, he wrote in a paper published in 2008, "highlights the importance of seeking out original sources of information and performing spatially extensive fieldwork. Results presented here further illustrate that although thermal influences appear to be the single strongest determinant of pika distribution currently, such influences interact with a number of other factors to determine persistence."
Furthermore, Dr. Beever told the Traveler last week that in British Columbia there currently are "robust densities" of pikas.
Reached at her office in California, Dr. Millar, a paleoecologist with a Ph.D. in genetics who currently is focused on "the role of historic and ongoing climate change in high-elevation forest biogeography, demography, and adaptation," attributed her findings in part to looking for pikas in areas where others hadn't and in part to having developed a recognition of optimal pika habitat.
"It’s a very wide-ranging species so it wouldn’t be surprising that the situation differs in different locations. So, where I happen to focus, the High Sierra, the eastern Sierra, in particular, it’s really not surprising. People really haven’t looked there," she says. "There just hadn’t been a systematic look. We have such an abundance of habitat, and high connectivity and high stratification across elevations that people don’t get out much onto those taluses and that happens to be where I work."
Drs. Millar and Beever both have surveyed pika populations in the Great Basin, though with little overlap. What Dr. Millar has found in her field work in the basin is that the talus conditions and habitat in general are not as favorable for the mammals as that found in the Sierra Nevada.
“Pika habitat in the Great Basin is more fragmented, and mountain ranges are highly isolated from one another. This diminishes the capacity of pika to move between taluses within a range, and to move between mountain ranges,” she says. “Our surveys were far less extensive in central Nevada ranges (Shoshone, Toiyabe, and Toquima) than in the Sierra Nevada and adjacent southwest Basin ranges, but where we did survey, we looked from low elevations to highest elevations in the region. What we found, however, was a significantly lower current occupation of taluses across a narrower elevation range than in the Sierra Nevada.”
Possible explanations for lower pika numbers range from environmental factors, including climate change, to disease or competition for habitat, says Dr. Millar. It also could be due to the “the fragmented nature of habitat in the Great Basin (which could lead to less migration), relatively poorly quality of habitat, and great isolation of ranges in Nevada,” she continues.
These factors, when combined, could mean that pika populations are not “declining relative to past (numbers), just that ‘equilibrium conditions’ are lower,” says Dr. Millar.
Dr. Beever, though, remains firm in his conclusions, and notes that other researchers have followed his footsteps and reached the same findings.
“When we say the species is gone from a site, I have very high confidence in that assessment," he says during a telephone call from Anchorage, Alaska. “We’re not seeing pikas just come back into places where they’ve been lost from, at the level of entire sites. We’re also not seeing great recoveries of population in terms of lower elevational limits."
A strong supporter of Dr. Beever's findings is the Center for Biological Diversity, the non-profit group that failed earlier this year to get the U.S. Fish and Wildlife Service to agree that the American pika is threatened by climate change.
“I guess what stands out to me is Connie Millar’s study provides a snapshot of where pikas are present in the Sierra Nevada, but in-depth studies looking at pika populations over time are finding that pikas are declining," says Dr. Shaye Wolf, a biologist with the center who specializes in population ecology. “Connie’s study is telling us where pikas are present in the Sierra Nevada, but not whether those pika populations are healthy or persistent. So I think the study has value in providing a baseline of where pikas are now in the Sierra Nevada, but that it will require future work and in-depth studies over time to figure out whether those pika populations are healthy and whether they will persist under warming climate conditions.”
Both Dr. Beever and Dr. Wolf questioned how many others could successfully and confidently apply the "rapid assessment" protocol in the same manner that Drs. Millar and Westfall used to identify pika populations. In it, researchers look for one of the following signs: an actual sighting of a pika or hearing its "chee-chee-chee" warning call; fresh urine, which leaves a white, milky stain on rocks; scat, which Dr. Millar said "are basically a little like BB-gun shot" and which are dark brown when fresh, or; haypiles.
"If there's green vegetation (in the haypiles), you know for sure it’s a currently used site. If there’s brown vegetation it’s within the last few years," she says.
But Dr. Beever, who bases pika presence only on a sighting, hearing its call, or finding recent haypiles, questions how many researchers could recognize that urine or scat is "fresh" and distinguish pika urine stains from stains made by other mammals that also use talus.
“I’ve talked with Connie about it, and I like Connie, she’s great," he says. "And I expressed with her my concern that even if she feels really confident in being able to assess when a fecal pellet -- understand that these fecal pellets are about 2 to 2.5 millimeters in diameter, so they’re very, very small, and they’re spherical -- so where she feels really confident about her ability to determine whether those are fresh or not, I have been more conservative in my approach in the sense that I do not consider fecal pellets alone as evidence of the species’ presence. And I told her that. I said, 'Even if you’re confident, I’m not confident that that’s a repeatable method'."
While Dr. Wolf questions Dr. Millar's contention that the pika populations she found were "thriving," Dr. Millar says that was evident from the many sites she was able to verify presence of the mammals. In one area in California's Mono Basin on the eastern edge of the Sierra she found pikas spread over 6,000 feet of elevation.
"By and large, where we looked in the Sierras the sites appear to be close to saturated," says Dr. Millar. "The other justification for that statement is the range limits that we found were greater than historic, so it’s hard to say a species is doing poorer than in the past if they’re expanding their range in all directions.”
In the end, she says, when it comes to climate change it's very difficult to make broad assessments of pika presence or population vigor without extensive field work.
"If you use global or hemispheric, or even regionally down-scaled climate projections onto mountains, and then you use that information to speak about a particular habitat in the mountains, you're likely to be off," says Dr. Millar, "because there’s so much micro-climatic process variability. Slope by slope, aspect by aspect, cirques are different then mountain-top summits, taluses are different than slopes adjacent that are just ground.
"So once you get down to the scale of something that affects the pika, you can’t say they’re just going to walk off the top of the mountain because it’s getting warmer."
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