Search for: All records

Pikas are captured, anesthetized, marked with colored ear-tags, non-lethally sampled, and released at point of capture during June-October. Study sites include a gradient of elevation and slope aspect, allowing a comparative study of pika response to variation in climate and sub-surface microclimate. Daily variation in snow cover and sub-surface temperatures are measured using data loggers placed within the territories of marked pikas. Focal territories are revisited at least once to characterize available vegetation via transect sampling and at least annually to service data loggers and record pika survival. Samples collected for genetic and physiological studies include ectoparasites, blood, saliva, urine, feces and hair as well as records of sex, stage, reproductive status, weight, foot length and body temperature. 

Long-term monitoring of habitat occupancy can reveal patterns of habitat use, population dynamics, and factors controlling species distribution. The American pika (Ochotona princeps), a small mammal found in rocky habitats throughout western North America, has been targeted for occupancy studies due to its relatively conspicuous behavior and its unusual adaptations for surviving long, cold winters without hibernation. These adaptations include an unusually high resting metabolic rate and maintenance of body temperatures near the lethal maximum for this species, which would appear to compromise the pika's ability to survive warmer summers. Recent monitoring as well as projections based on future climate scenarios have suggested this species is experiencing a period of range retraction due to warming summers and/or loss of insulating winter snow cover. Niwot Ridge is situated ideally to test competing hypotheses about the trajectory and drivers of pika range shift. The pika is still common throughout the Colorado Rockies, but published models differ markedly regarding projections of the pika’s future distribution in this region. Niwot Ridge has experienced warmer summers as well as shorter periods of insulating snow cover in recent years, and there is evidence that pikas are now less common than they once were in at least one area on the ridge. This study is designed to provide robust data on pika population trends through long-term monitoring of occupancy in a spatially balanced random sample of pika habitat patches centered on Niwot Ridge. Survey plots (n = 72) were selected according to a Generalized Random-Tessellation Stratified (GRTS) algorithm, stratified dichotomously by elevation, average annual snow accumulation (SWE), and probabilities of pika occurrence based on previous data. Each plot extends 12 m in radius from a GRTS point. To ensure that each plot contains at least 10% cover of talus, plot coordinates were adjusted (usually less than 50 m) or replaced using the GRTS oversample to select the next available and suitable plot within the same categories of elevation, SWE and probability of occurrence (see "pika-survey-GRTS-plot-tracking-record.cr.data.csv" for plot strata, survey schedules, GRTS sequence, and records of plot replacement or location adjustments). Trained technicians survey plots for pikas and fresh pika sign (food caches and fecal pellets) as well as metrics of habitat quality. Each year, 48 of the 72 plots are surveyed in a rotating panel design (24 plots are surveyed annually, 24 in even years and 24 in odd years). Plots are surveyed in August when pikas are engaged in food caching and other conspicuous behaviors related to territory establishment and defense. Data collected at each plot are detailed in a survey manual ("pika_survey.cr.methods.docx"). Each plot is outfitted with a data logger (sensor) to record sub-surface temperature several times each day. Photos of plot and sensor locations are used in navigation and sensor retrieval. Each survey is completed during a brief (half-hour) visit to the plot to service the sensor and to record habitat and pika data. A subset of plots (n = 12) are selected for double surveys each year to allow estimation of pika detection probability. Estimates of detection probability are also informed by data on time to detection of pikas and pika sign recorded during each survey. Samples of fresh pika fecal pellets are collected from occupied plots and are stored as vouchers of pika presence and for use in studies of population genetics and physiology, including studies of physiological stress in relation to habitat quality and microclimate. 

Long-term monitoring of habitat occupancy can reveal patterns of habitat use, population dynamics, and factors controlling species distribution. The American pika (Ochotona princeps), a small mammal found in rocky habitats throughout western North America, has been targeted for occupancy studies due to its relatively conspicuous behavior and its unusual adaptations for surviving long, cold winters without hibernation. These adaptations include an unusually high resting metabolic rate and maintenance of body temperatures near the lethal maximum for this species, which would appear to compromise the pika's ability to survive warmer summers. Recent monitoring as well as projections based on future climate scenarios have suggested this species is experiencing a period of range retraction due to warming summers and/or loss of insulating winter snow cover. Niwot Ridge is situated ideally to test competing hypotheses about the trajectory and drivers of pika range shift. The pika is still common throughout the Colorado Rockies, but published models differ markedly regarding projections of the pika’s future distribution in this region. Niwot Ridge has experienced warmer summers as well as shorter periods of insulating snow cover in recent years, and there is evidence that pikas are now less common than they once were in at least one area on the ridge. This study is designed to provide robust data on pika population trends through long-term monitoring of occupancy in a spatially balanced random sample of pika habitat patches centered on Niwot Ridge. Survey plots (n = 72) were selected according to a Generalized Random-Tessellation Stratified (GRTS) algorithm, stratified dichotomously by elevation, average annual snow accumulation (SWE), and probabilities of pika occurrence based on previous data. Each plot extends 12 m in radius from a GRTS point. To ensure that each plot contains at least 10% cover of talus, plot coordinates were adjusted (usually less than 50 m) or replaced using the GRTS oversample to select the next available and suitable plot within the same categories of elevation, SWE and probability of occurrence (see "pika-survey-GRTS-plot-tracking-record.cr.data.csv" for plot strata, survey schedules, GRTS sequence, and records of plot replacement or location adjustments). Trained technicians survey plots for pikas and fresh pika sign (food caches and fecal pellets) as well as metrics of habitat quality. Each year, 48 of the 72 plots are surveyed in a rotating panel design (24 plots are surveyed annually, 24 in even years and 24 in odd years). Plots are surveyed in August when pikas are engaged in food caching and other conspicuous behaviors related to territory establishment and defense. Data collected at each plot are detailed in a survey manual ("pika_survey.cr.methods.docx"). Each plot is outfitted with a data logger (sensor) to record sub-surface temperature several times each day. Photos of plot and sensor locations are used in navigation and sensor retrieval. Each survey is completed during a brief (half-hour) visit to the plot to service the sensor and to record habitat and pika data. A subset of plots (n = 12) are selected for double surveys each year to allow estimation of pika detection probability. Estimates of detection probability are also informed by data on time to detection of pikas and pika sign recorded during each survey. Samples of fresh pika fecal pellets are collected from occupied plots and are stored as vouchers of pika presence and for use in studies of population genetics and physiology, including studies of physiological stress in relation to habitat quality and microclimate. 

Many animals are herbivores, which means they get all their nutrients from eating plants. American pikas are cute rabbit relatives that eat plants in the mountains. But alpine winters are harsh, so pikas spend their entire summer gathering and storing plants to eat under the winter snow. Just like people, pikas in Colorado have a favorite food: a plant called alpine avens. This plant species is a special pika snack because it contains natural preservatives called phenolics, which keep the food fresh all winter. We studied how climate change is affecting this important feature of the pika’s favorite meal. Alpine avens contains more phenolics now than it did 30 years ago, so they preserve better in storage. But there is a catch: these preservatives can be hard to digest. Studies like this help us start to understand the many complicated ways that climate change affects herbivores like pikas. 

Climate change in mountain regions has exposed high-elevation species to rapidly changing temperatures. Although climate exposure can be reduced in certain microclimates, the quality of microclimatic refugia might also degrade with climate change. The American pika ( Ochotona princeps ) often inhabits high elevations, and is considered climate-sensitive due to its narrow thermal tolerance and recent extirpations in some warmer portions of its range. Pikas behaviorally thermoregulate by taking refuge in the subsurface microclimates found in taluses and other rocky habitats, where daily thermal fluctuations are attenuated and somewhat decoupled from free-air temperatures. Changes in microclimate might reduce the efficacy of this behavioral thermoregulation. This study compares recent (2009–2021) subsurface temperatures at a long-term pika study site with a rare instance of historical (1963–1964) data from the same location. We also place historical and recent microclimates in context using long-term data on free-air temperatures from the same area. Recent free-air temperatures were often warmer than historical records, and subsurface temperatures exhibited even stronger warming between periods. Temperatures measured in the talus were often dramatically warmer in recent records, especially at the deeper of two subsurface sensor placements in this study. Winter months showed the greatest changes in both talus and free-air temperatures. Differences between historical and recent microclimates were not explained by the precise placement of sensors, as recent temperatures were similar across a wide variety of subsurface placements, and temporal changes in free-air temperatures at the historical study site were also reflected in data from nearby weather stations. Together, these results suggest that subsurface microclimates important for pika thermoregulation have changed over the past few decades, perhaps even faster than observed changes in free-air temperatures. The generality of these results and their potential ramifications for ecosystem processes and services should be explored. 

Abstract BackgroundDistributional responses by alpine taxa to repeated, glacial-interglacial cycles throughout the last two million years have significantly influenced the spatial genetic structure of populations. These effects have been exacerbated for the American pika (Ochotona princeps), a small alpine lagomorph constrained by thermal sensitivity and a limited dispersal capacity. As a species of conservation concern, long-term lack of gene flow has important consequences for landscape genetic structure and levels of diversity within populations. Here, we use reduced representation sequencing (ddRADseq) to provide a genome-wide perspective on patterns of genetic variation across pika populations representing distinct subspecies. To investigate how landscape and environmental features shape genetic variation, we collected genetic samples from distinct geographic regions as well as across finer spatial scales in two geographically proximate mountain ranges of eastern Nevada. ResultsOur genome-wide analyses corroborate range-wide, mitochondrial subspecific designations and reveal pronounced fine-scale population structure between the Ruby Mountains and East Humboldt Range of eastern Nevada. Populations in Nevada were characterized by low genetic diversity (π = 0.0006–0.0009; θ_W = 0.0005–0.0007) relative to populations in California (π = 0.0014–0.0019; θ_W = 0.0011–0.0017) and the Rocky Mountains (π = 0.0025–0.0027; θ_W = 0.0021–0.0024), indicating substantial genetic drift in these isolated populations. Tajima’sDwas positive for all sites (D = 0.240–0.811), consistent with recent contraction in population sizes range-wide. ConclusionsSubstantial influences of geography, elevation and climate variables on genetic differentiation were also detected and may interact with the regional effects of anthropogenic climate change to force the loss of unique genetic lineages through continued population extirpations in the Great Basin and Sierra Nevada. 

Abstract Climate change is increasing temperature, decreasing precipitation, and increasing atmospheric CO₂concentrations in many ecosystems. As atmospheric carbon rises, plants may increase carbon‐based defenses, such as phenolics, thereby potentially affecting food quality, foraging habits, and habitat suitability for mammalian herbivores. In alpine habitats, the American pika (Ochotona princeps) is a model species for studying effects of changing plant chemistry on mammals. To survive between growing seasons, pikas cache “haypiles” of plants rich in phenolics. Although they are toxic to pikas, phenolic compounds facilitate retention of plant biomass and nutrition during storage, and they degrade over time. Alpine avens (Geum rossii, Rosales: Rosaceae) is a high‐phenolic plant species that comprises up to 75% of pika haypiles in Colorado. Here, we tested the hypothesis that contemporary climate change has affected the nutritional value of alpine avens to pikas in the last 30 years. Specifically, we compared phenolic activity, nutritional quality, and overwinter preservation of plants collected at Niwot Ridge, Colorado (USA), in 1992 to those collected between 2010 and 2018, spanning nearly three decades of climate change. Phenolic activity increased in alpine avens since 1992, while fiber and nitrogen content decreased. Importantly, overwinter preservation of plant biomass also increased, particularly on windblown slopes without long‐lasting snow cover. Previous studies indicate that pikas at this site still depend on alpine avens for their winter food caches. Higher phenolic content in alpine avens could therefore enhance the preservation of haypiles over winter; however, if pikas must further delay consuming these plants to avoid toxicity or invest extra energy in detoxification, then the nutritional gains from enhanced preservation may not be beneficial. This study provides important insights into how climate‐driven changes in plant chemistry will affect mammalian herbivores in the future.