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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.
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This content will become publicly available on February 1, 2026
Combining past and contemporary species occurrences with ordinal species distribution modeling to investigate responses to climate change
Many organisms leave evidence of their former occurrence, such as scat, abandoned burrows, middens, ancient eDNA or fossils, which indicate areas from which a species has since disappeared. However, combining this evidence with contemporary occurrences within a single modeling framework remains challenging. Traditional binary species‐distribution modeling reduces occurrence to two temporally coarse states (present/absent), so thus cannot leverage the information inherent in temporal sequences of evidence of past occurrence. In contrast, ordinal modeling can use the natural time‐varying order of states (e.g. never occupied versus previously occupied versus currently occupied) to provide greater insights into range shifts. We demonstrate the power of ordinal modeling for identifying the major influences of biogeographic and climatic variables on current and past occupancy of the American pikaOchotona princeps, a climate‐sensitive mammal. Sampling over five years across the species' southernmost, warm‐edge range limit, we tested the effects of these variables at 570 habitat patches where occurrence was classified either as binary or ordinal. The two analyses produced different top models and predictors – ordinal modeling highlighted chronic cold as the most‐important predictor of occurrence, whereas binary modeling indicated primacy of average summer‐long temperatures. Colder wintertime temperatures were associated in ordinal models with higher likelihood of occurrence, which we hypothesize reflect longer retention of insulative and meltwater‐provisioning snowpacks. Our binary results mirrored those of other past pika investigations employing binary analysis, wherein warmer temperatures decrease likelihood of occurrence. Because both ordinal‐ and binary‐analysis top models included climatic and biogeographic factors, results constitute important considerations for climate‐adaptation planning. Cross‐time evidences of species occurrences remain underutilized for assessing responses to climate change. Compared to multi‐state occupancy modeling, which presumes all states occur in the same time period, ordinal models enable use of historical evidence of species' occurrence to identify factors driving species' distributions more finely across time.
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- Award ID(s):
- 2022036
- PAR ID:
- 10621587
- Publisher / Repository:
- Ecography
- Date Published:
- Journal Name:
- Ecography
- Volume:
- 2025
- Issue:
- 2
- ISSN:
- 0906-7590
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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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.more » « less
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